May 1964 Same Old 40c
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PIONEERS IN MINI A TURIZA TION
"A-SERIES
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AUDIO TRANSFORMERS & INDUCTORS
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TYPE A CASE
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FOR TRANSISTOR i TUBE APPLICATION
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with high conductivity oute case, effects good inductiv shielding. The die cast case pre vides top and bottom mounting These units are adaptable fo printed circuit use.
The conservative design am manufacturing procedures em ployed make these units suitabl< for virtually all types of commer cial equipment and ideal fo quality amateur service.
Write for latest catalog of over 1,200 STOCK ITEMS with UTC high reliability
UNITED TRANSFORMER CORP.
150 VARICK STREET, NEW YORK 13, N.Y.
PACIFIC MFG. DIVISION: 3630 EASTHAM DRIVE, CULVER CITY. CALIF.
EXPORT DIVISION: 13 EAST 40*h STREET, NEW YORK 16, N. Y. CABLE: "ARLAB"
73
Magazine
Wayne Green W2NSD/1 Editor, etcetera
ing Noise Lock
Matching VHF Antennas
K2TKN
K5JKX
Where Have our Bands Gone? W2DUD
The Quad-Quad
12
16
» » i j v + ■* ■ i
W8HHS 20
Class D Amplifier
K5JKX
26
12 Volts from 6
K6BIJ
32
May, 1964
Single Tube Oscillator-Multiplier
K5JKX
34
Vol. XIX, No. 1
SSB, DSB, AM, etc.
■ *. -k
K6HJH
r fe ■ I
36
Inboard Calibrator for the NCX-3
WB2MAH
42
Push-to-Talk for the HT-37
W2ZBS
46
Gardner Modulator Revisited
WA2AKK
50
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73 Magazine Is published monthly by 73, Inc., Peterborough, N. H. The phone number is 603-924-3873. Subscription rates have just been hiked (after considerable warning) to $4.00 per year, $7,00 for two years, $10 for three years world wide. Second class postage is paid at Peterborough, New Hampshire and at additional mailing offices. Printed in the U.S.A. Entire contents copy- right 1964 by 73, Inc. Postmaster: please send form 3579 to 73 Maga- zine, Peterborough, New Hampshire.
Now Hear This, Fellow Amateur
W4LCY
Frequency Standard W2LYH
More on the Vertical J
Big Brother and How He Grew
Amateur Radio Emergency Service
Correspondence from the Members
TVI
K5JKX
K4ZJF
K7KYG
k i ■ ■ ■
I P ■ ■ ■ ■* ■ i
K6BIJ
54
60
62
64
68
69
* ■ m *
76
Novice Transmitter
K1WXY 78
H«S*T\
XYL-G3NMR
80
Hobbyist? Write!
■ m m
W1MEG
83
Letters 71, 74
New Products
72
MAY 1964
1
W2NSD/1
never say die
Why Johnnie Can't Read
It's too painful, I can sympathize with John's problems. It must really bug him to get erudite letter after erudite letter telling him and the ARRL off. each with that little "cc to 73" at the bottom. Ill try to bring you little samples of the mail that somehow never makes it into QST in our letters department
I understand that at a club meeting down in New Jersey in mid March, attended by Huntoon, a "League Official" publicly doubted the validity of the 73 poll of amateur opinion on RM-499. Johnnie, stop deluding yourself. The results of the poll are accurate and you know it, It doesn't seem possible that even wishful thinking could put that nagging figure of 80% opposed to 499 out of mind. Not only did the 73 poll give this figure, but we find the same proportion when we examine the FCC files on 499 in Washington. The mail received provides a similar tally, as do polls at hamfests where a count is taken without a Hoover brainwash,
Johnnie, even the polls being taken by your own Directors are giving you almost the same results (which you don't dare publish in QST), Wake tip old boy. Don't try to sell us that 50-50 jazz, we all know it isn't so.
Johnnie, why don't you send Dick and a helper up here to count the ballots, I'll provide gas money round trip for them (from Con- necticut) plus room and board while they are counting . . . (limit 30 days room and board to this offer), They will be provided all of the ballots we're received, our capitulation sheets, computer, a card table, and two camp chairs. We hope they'll be up for a visit and bring along a list of all of the chaps that they know of who have sent in favorable ballots to check against our ballots. They're all here, every last one of them , . . and a pitful few favorable votes there are.
World's Fair
The Worlds Fair in New York is an obvious place to show off our great hobby. Here is a place where we could show millions of people, including in all probability, virutally every foreign dignitary in the world, the value of amateur radio to our country. What a mar- velous place to display evidence of the equip- ment we can design and build for ourselves, evidence of our unique ability to perform public service, and our ability to bring the world together through people-to-people com- munications.
Hun toon , . . front and center for a couple questions.
Johnnie, who, exactly made the arrange- ments for the exhibit? Who called Coca-Cola and suggested the exhibit? Who decided, and what influenced him to decide, that this ex- hibit would not contain one single item of home constructed equipment? Why have you decided to install a complete "appliance operators" setup? How did you manage to con the trusting clubs of the Hudson Division into agreeing to man this completely commercial installation? How are you going to explain this to your Directors this month? Will they accuse you of hypocrisy for talking technical achievement on the one hand and then pushing commercial equipment when it comes to a show down? Will they wonder why the equip- ment of one single manufacturer was chosen instead of using a cross section of several manufacturers? How will you explain this decision to all of the other manufacturers?
ARRL Fights Back
Since I have been sorely vexing the ARRL of late I naturally expected some sore vexation in retribution. The S. V, has arrived, "73 Magazine is not acceptable as an exhibitor at the 1964 ARRL National Convention." My vex is very sore. It fair brings tears to my eyes
73 MAGAZINE
SI N G L
IDE
AND
FILTE
ACF-4
9 mc center frequency
Bandpass 6 db 3 kc (approximate)
ACF-2 Two -crystal filter circuit using low impedance link input and 2K resistive output load, Unwanted sideband rejection greater than 30 db. $9.95
ACF-4 Four-crystal filter cir- cuit using nominal 600 ohm input and output: Unwanted sideband rejection greater than db. $18,95
WRITE TODAY
FOR
YOUR
|
iy S3 " /;•■ ■'.■■•; v |
|||
1964 CATALOG
ACF-6 Six-crystal filter circuit using nominal 600
ohm input and output, Unwanted sideband rejection
greater than 55 db. $27.95
MATCHING OSCILLATOR CRYSTALS for the ACF
filter series. Recommended for use in 03-4 oscillator. CY-6-9LO $4.40 CY-6-9HI $4.40
OS-4 Crystal Oscillator $6.95
SE-6F Mounting Case
Special AOC case for mounting filter plates,
$5.50
* Add-On-Circuit
International Crystal Mfg. Co., Inc.
18 North Lee, Oklahoma City, Oklahoma
Please rush 1964 catalog.
Address.
City.
PLEASE PRINT
Zone ^State,
* ,. BE
^*>»u
*W*
c r y!
NC.
18 NORTH LEE • OKLAHOMA CITY, OKLA.
MAY 1964
o
the LEADER in
CRANK-UP
TOWER
DESIGN
The full-strength Hercules 66-3 has diagonal bracing— a unique feature in all E-Z Way Towers. It's designed to support a large 20 m or 40 m beam; 4 eL Du-band; or 6 el Triband Wind area 22 feet at 66 feet in 60 MPH winds.
The 3 sections of the Hercules tele- scope from a minimum height of 30 feet to a maximum 62 feet. A worm gear winch tilts the tower over for easy access to your beam.
n
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MODEL TORBZ 66-3 |
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&955.00i |
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WIND LOAD CHART |
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Ant |
Full |
Height Half Height |
Min. |
Height |
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Model Wind Area |
MPH |
Hgt. MPH |
Hgt. |
MPH |
||
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TORBZ 66-3 |
22.2 |
66 |
60 |
50 86 |
32 |
[25 |
|
TORBZ 66-3 |
13,2 |
66 |
75 |
50 90 |
32 |
140 |
|
TORBZ 66-3 |
Z2 |
66 |
90 |
50 100 |
32 |
150 |
|
TORBZ 75-3 |
17.0 |
75 |
60 |
55 86 |
33 |
125 |
|
TORBZ 75-3 |
10,0 |
75 |
75 |
55 100 |
33 |
140 |
|
TORBZ 88-3 |
12 |
88 |
60 |
65 36 |
38 |
140 |
NEW E-Z WAIT HERCULES DELIVERS THE ULTIMATE IN TOWER POWER
HERCULES Painted Galvanized
TORBZ 66-3 955.00 1.095 00
TORBZ 75-3 l(055.0O 1,240.00
TORBZ 88 3 1,187.50 1393 50
100'
MOTOR WINCH
The E-Z Way Motor Winch raises ami lowers towers to any height with- out guys. When towers are motorized a larger beam can be used because the tower is normally lowered to safer elevations. Standard features: Combination worm gear drive; totally enclosed motor and gear box; remote control switch; spiral grooved winch drum; positive crank down and limit- er switches. Assembled complete with hardware and instructions, just $389,50 for TORBZ 66-3; $399.50 for TORBZ 75-3 and $495.00 for TORBZ 88-3.
E-Z WAY TOWERS, INC
5901 E, BROADWAY TAMPA, FLORIDA
when I think of the tens of loyal ARRL camp followers who will be robbed of their golden opportunity to spit epithets in my face. My heart renders when I think of the hundreds of dollars we will save in not driving all the way down to rotten old New York in the middle of ghastly August. I tremble in dismay when I think of the poor families of those gouging porters who take hours to carry a small box to our postage stamp sized $200 exhibit space . . . the one over in the comer behind the pole. Alas, I will miss those canasta games with the other exhibitors while waiting vainly for someone to come to our exhibits > even if only to try to steal something.
It is not terribly depressing, when one has completely accepted a seemingly unavoidable unpleasant fact, to suddenly be reprieved. Virginia and I had decided that inspite of the first Hudson Convention back in I960, which we considered a fiasco, and the second in 1962, which we prudently avoided (if we are to believe the dismayed groans of some of those who did attend) j that we would support the National Convention this year, even if it cost us our shirts.
If you really want to see 73 at the Conven- tion and promise to buy a subscription, some booksj or maybe an Institute membership, then first you've got to convince Huntoon to change his mind, Now I doubt if Hunty changes his mind easily, particularly when he*s emotionally upset, so you 11 have to be very convincing. The basic question is this: is it really fair* for the ARRL to force us to save all that monev bv such a sneakv action?
My March editorial apparently bugged Huntoon for a mailing went out to all affiliated clubs picking out three of my hints at possible things to come, labeling them flagrant misin- formation. No doubt a few clubs will dutifully pass along this letter as Gospel It is bound to happen that some will look into 73 and see that there is a lot more flagrant information than flagrant misinformation,
Auto-Call, the club paper for 17 radio clubs in and around Washington, D, C, de- voted considerable space to my editorial, including many quotes from it.
RM-499 W4TYH and K3VUQ went through the FCC flies on RM-499 and reported that there were about 3000 items in nine file folders. Some were petitions, some were individual comments, others were letters of inquiry. It took all one day to sort out the mass, They found that between 80 and 85% of the amateurs
(Turn to page 85)
73 MAGAZINE
*sss§&
with the NEW
HAMMARLUND HXL-1 linear amplifier
Regardless of the exciter you are now using — the HX-50. the HX-500, or any one of a host of compatible competitive units, yon will TAKK COMMAND the moment you're hooked up to the incredible HXL-1,
The HXIi-I is so rugged, it can be held 'key down1 at a kilowatt for more than an hour * . . without damage. It delivers the full metered le^al power of 1 KW CW input- — tWO W PEP input. Here is a "no-nonsense" linear that delivers the power you pay for — the performance you want.
fiend for complete technical literature today — or see and try it at your nearest authorized Hammarlund distributor,
FEATURES
Complete coverage— 80 to 10 meters
Broad Banded Input Circuit
3 Element adjustable Pi network output
Built-in multi-purpose meter including linearity test
Control circuitry compatible with most transmitters and transceivers (i.e. HX-50, HX-500, "S" line and KWM1, KWM2, etc.)
Efficient Ground-grid circuit using 2 high dissipation triodes (United 572A)
Husky, self-contained solid state power supply with silicon rectifiers
Only connection required between exciter and amplifier is a coax cable. All relay switching built into amplifier.
Power nacked performance on SSB. CW and AM. 1500W PEP input; 1 KW CW input
Designed for 115/230 volt operation
Same physical size as the Fabulous HX50. (17V2" wide; 9V2" deep; 9Va" high)
HRfTintRRLUND
MANUFACTURING COMPANy/a GIANNIIMl SCIENTIFIC COMPANY 53 West 23rd Street, New York 10, New York
Cable Address: SUPERPRO
|mi*i*iii I tit
MAY 1 964
Bill Ashby K2TKN Box 97 — Sunset Lake Pluckemin, N, J.
Strong Noises
or
The Flying Noise Lock System
Like the weather, everv one cusses noise but few attempt to do much about it, except trying to learn to squint their ears, which isn't easv*
Noise comes in various forms and intensities and it is pretty hard to find any two of the hundreds of noise definitions in print that describe the same thing.
For our purposes, let's say noise is detectable energy that never happens twice in the same place or the same way.
This lets out ignition noise, power line leaks, rotating or vibrating contact arcing; i.e.; repe- titious pulse trains of wide bandwidth; for modem circuitry— noise bl ankers— rhododendron swamp hole punchers, etc., have pretty well settled their hash.
We are talking about electron motion noise. That non-coherent crud that is generated in infinite amounts throughout the whole galactic universe; measurable amounts when current is passed thru a hot resistor ; and microwatts of which, in the input stage of any receiver, keeps us from hearing weak signals, "Johnson noise" as it is usually termed, is smooth and evenly distributed, but totally non-coherent If a channel of 10 kc width centered at 450 kc was mixed with a channel of 10 kc bandwidth of the same shape factor but centered at 460 kc in a linear mixer the noise in each channel would neither add nor subtract, you would just get noise. The instantaneous peak value de- pending on the value in either channel at that instant and the gain or loss in the linear mixer.
This is an extremely controversial subject and the above definition treads on some highly educated toes, but remember nothing was men- tioned about averages, non-linear detection, pre- or post-detection integration or attempting to measure finite values of noise power. All of these complicate the above picture to the nth degree and has been known to drive long friends at each other's throats with bare knuckles, knashing teeth and bloodshot eye.
Since we aren't going to discuss any of these,
let alone try to use them in practical circuits, we will let the communication theory hounds worry these points into obscurity*
If you were to look at the output of one of the foremen tioned if channels with a wide- band, ultra-fast rise and fall-time scope operat- ing well below the overload point, you would describe the pattern as very fine, continuously changing grass growing equal distances up and dawn. Widening the pass-band of the if chan- nel would make the grass finer in changing detail and severely nan owing it would give a coarse, ever changing structure. At any instant in time it can have any amplitude, frequency or phase and it may or may not be the same at any other instant— in other words, complete n on -coherence. It is extremely doubtful that noise in this state can be modulated or detected without serious changes in its basic structure.
Mixtures of verv weak signal and lots of this type of noise are extremely difficult to picture. It is not really known if the noise rides on top of the signal or vice versa or whether they just intermingle. We do know that any at- tempt to measure or detect any part of this mixture with a non-linear or averaging circuit of any kind wipes out the smaller variations and squelches out the weak signal. By weak signal, we mean one whose peak value is 20 to 30 db under the peak values of the associated Johnson noise in the circuit. By using all linear circuits in your revr (product detector-BFO, etc.) CW signals that are 30 elb below the peak value of the noise can be heard and with long practice slow CW can be read by a very expert ear when approximately 20 db below the noise peaks, It is doubtful that unknown signals of these intensities can be located or acquired by tuning this type receiver unless they peak up occasionally to much higher levels.
The commercials and military people have a number of systems that can pass useful in- formation over circuits where the received signal is this far down in the noise. The majority of these are closed loop systems of
6
73 MAGAZINE
SIGNAL INPUT
C-24V DC. OUTPUT
~~T*T~™
n
u
n
REFERENCE INPUT
FIGURE I
little value to independent amateur operation. In these, some definite form of information is included in the transmitted signal and the re- ceiver does not actually detect but correlates to locate this pattern of information out of the morass of noise. Another way to describe this —a key shaped block will only pass thru a key shaped hole— the round, square, oblong and triangular ones are ignored. If the receiver knows exactly the frequency— in fact, the exact received phase of the desired signal, then dig- ging 30 db inside the peaks of noise is no prob- lem.
What then, could two independent amateurs, half way around the world from each other, do to realize some measure of improvement in very weak signal in the presence of strong
noise reception? This might be on 20 meters when the band is dead or on 432 mc using the moon as a reflector, but we must have a chan- nel that is free of QRM. We want to get below that weak signal threshold that is so apparent in every receiver when a weak signal fades abruptly into the Johnson noise of its front end- Many schemes have been tried by various amateurs— use of WWV as the phase lock iden- tification; Dicke Astronomy setups with high speed switching between antenna and con- trolled noise source with, synchronous detec- tion, to achieve a hair-bigger balance that nulls out all receiver noise; and the only one that has given any concrete results— fantastic stabilization of the transmitted frequency to the extent that phase coherence between it
10 V ZENER
EITHER
BAl mod,*™-
OUTPUT O^^-T TERMINAL
SQUARE
WAVE OUTPUT
FIGURE 2
-Z4V.
MAY 1964
and a stable BFO could he integrated inside a human head. A number of simple and very complex open loop phase-lock systems have been attempted (AFC of the L.O. or BFO to stay in phase stable relationship to received signal) but all seem to require very strong signal peaks to lock up so aren't much good, or noise peaks kick them off the desired signal, which is disastrous.
Flying Noise-Lock System
In experimenting with many variations of a number of the above systems, it became ob- vious all depended on a phase detector that really was just that. It had to be linear to both signal and noise and to give output that was a true measure of phase between a known and an unknown and to reject by at least 30 db any improperly phased inputs and particularly suppress input amplitude variations for these would be primarily noise. Since inventing such a circuit could be hard work I spent some time in research (lifted the circuit from a piece of equipment designed for another purpose). This is a double-balanced modulator that reallv is almost idiot-proof (Figure 1),
The diagonally opposed transistors are switched on and off by the square wave refer- ence frequency. When they are switched on they are amplifying in a linear manner during that half cycle* In this way when the incoming signal is exactly in phase with the reference, the two transistors connected to one collector load resistor draw increased current and the other two less so there is a several volt dc difference between the collector ends of the balanced collector load resistors, 180° phase difference reverses this dc difference, and random phase gives zero dc output.
Random phase relative to the references or
amplitude variations at either input such as noise result in some noise output but this will be attenuated bv at least 30 db if the circuit is not overloaded.
Since the phase of a desired weak signal is not known, we are going to look for it. The very weak noise output from the balanced modulator caused by random phase and noise peaks is amplified in a linear dc amplifier and applied as AFC control to the base of a transistor whose collector-emitter circuit form a reference oscillator. The output of this is fed to a Schmitt trigger to form the sym- metrical square wave required by the bal- anced modulator. Just enough filtering time constant is used to keep the AFC circuit from oscillating, but yet allow a wide band of posi- tive and negative noise pulses to sweep the reference oscillator back and forth at random noise rates (Figure 2),
The result is very complex but can be simply described by the apparent action. It appears to lock up on every random noise pulse that gets thru the balanced modulator. If this pulse is moving in frequency— so does the reference os- cillator—locked on. During this instant there is dc output from the balanced modulator for the oscillator is either exactly in phase or out with the noise pulse and this establishes the flying lock. But a noise pulse doesn't last— it moves clear off frequency or dies in amplitude and at its AFC minimum threshold the circuit jumps to the next best noise pulse available. This may result in the oscillator locking up in the same phase or opposite resulting in dc out- put from the balanced modulator of opposite polarity. Because noise is completely random the output circuit flops back and forth in polari- ty and amplitude of dc in a totally random manner for there are are just as many flings as
FAIRLY BALANCED TRANSISTORS
50 Kt INPUT
SQUARE WAVE MP\JT
-£4V
FIGURE 3
8
71 MAGAZINE
There is just no better way of getting started in VHF than with the newest of the new in the Clegg line — the 22'er two meter transceiver. This ready-to-go station combines many of the fine features that have made the Clegg name famous in VHF ham circles for years plus re- finements to make 2 meter AM phone operation more interesting and challenging, It is realistic- ally priced — your distributor will have complete information.
Features
1. Triple conversion receiver with NUV1ST0R RF stage provides
a) Better than .25 /*v for 10 db s + n n
b) 8 KC selectivity with steep skirts
c) fmage rejection better than 50 db
2. Exclusive new receiver tuning system pro- vides extremely good frequency stability
3. Smooth Slide Rule Tuning Dial
4. Illuminated Panel Meter doubles as calibrated S meter on receive and "relative output'' meter for transmitter tune up
5. Effective Automatic Peak Noise Limiter on receiver
6. Built in Speaker
7. High level plate and screen modulation with speech clipping for typical Clegg "high talk power" performance
8. Broad Banded Transmitter Circuits for ease in QSY
9. Push to Talk
10. Transmitter frequency spotting switch
11. Provision for (external) linear amplifier and VFO
12. Conservative 11 watt rating (input)
13. Unit will operate with either 8 or 12 MC
crystals
14. Self contained universal power supply for 115 Volts AC and 12 Volts DC
|
15. Tube line-up |
l |
|
VI 6CW4 |
Rcvr RF |
|
V2 6DJ8 |
Mixer/VLO Tripler |
|
V3 6DJ8 |
VLO/Cathode Follower |
|
V4 6AU6 |
2nd Mixer |
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V5 6BA7 |
3rd Mixer |
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V6 6BA6 |
IF Amplifier |
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V7 6AL5 |
Diode detector/Noise Limiter |
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V8 12AX7 |
AF Amplifier AF Amplifier |
|
V9 6BQ5 |
Rcvr Audio Output Xmtr Modulator |
|
V10 6EA8 |
Xmtr XLO 1st Multiplier |
|
Vll 12BY7 |
Buffer Amplifier |
|
V12 12BY7 |
Xmtr Driver |
|
V13 2E26 |
Xmtr Final Amplifier |
Squires - Sanders, Inc
475 WATCHUNG AVENUE. WATCHUNG. N. J.
MAY 1964
9
Mi
INPUT
0-1 Mo CHART DRIVE
30 K
Switch omitted from rii^ir^m fur » imp licit?
Time Constant (sec] .001 .01
.1
1.0 10.0
C2-C3 (midt .0047
,047 .47
4 7 47.0
C4 fmfdj D] .1
1.0 10,0
100.0
-24 V.
FIGURE 4
there are Bangs even during a few miliseconds (Figure 3).
By means of a cathode or emitter follower, a volt or so of linear if signal is stolen from the last if in the station receiver. The BFO and all non -linear detectors must be decoupled or disabled.
This linear if output is fed to a split phase inverter to feed the double balanced modulator, rather than use a center tapped if transformer that could restrict or modify the frequency response at this point, The balanced driver transistors match the input impedance of the emitters of the balanced modulator. The total gain of these stages is not enough to produce non-coherent noise at the output without if input so that the reference oscillator rests on its natural frequency which should be ap- proximately centered in the if passband of the receiver.
Under normal operating conditions, observa- tion should be made occasionally with a high gain scope between the input Test Point and ground. Any evidence of signal at this point indicates severe overload of the balanced mod- ulator and i/-rf gain in the receiver should be reduced .
Tune the receiver across a fairly weak sig- nal, The reference oscillator will lock up as soon as the signal is in the pass band of the if and balanced modulator* Several volts of dc dif- ference is potential between the balanced modu- lator collector load output terminals will be in evidence. Upon tuning the signal thru the cen- ter of the if passband this dc output will flop to the opposite polarity as the reference os- cillator locks in the opposite phase. This will
hold till the signal is tuned out of the if passband and the reference oscillator AFC lets go and the oscillator heads for center, then random noise in the AFC loop starts the whole system searching at the noise rate again; it is looking for signal!
With very weak signals the operation of the flying noise lock system is slightly different. It will be necessary to add a high-gain, variable time-constant dc amplifier for the resultant dc shifts from weak signals may be 30 to 50 db below the peak swings from noise (Figure 4).
As outlined before, during no signal con- dition, the dc output from the balanced modu- lator flops back and forth at a random rate. By introducing longer time constants in the indicator amplifier, we can reduce the am- plitude of these swings caused by short pulses of noise without interfering with the circuits' abilitv to indicate dc shifts that are caused bv signals of longer duration than the time con- stant used,
Really weak signals will not indicate a locked up oscillator AFC but the indicator circuit will register more swings or "hits" toward one polarity than the other. Tuning across a very weak signal slowly will show increased hits toward first one side than toward the other as the signal modifies the phase on either side of the if passband.
This flying noise lock system tends to in- tegrate hits when signal is present even in extremely small amounts. Use of some time constant in the indicator amplifier slows down the irregular swings of the output due to nois< but doesn't in t ere fere with the output swinging over and staying there when signal is present
10
73 MAGAZINE
then going back to the irregular swings cen- tered around zero during no signal (Figure 5).
This Schmitt trigger circuit can be used across the recorded output of the indicator amplifier. This circuit keys the relay from the differential output and this keys an audio oscillator so slow CW can be read by ear. With very weak signal there will be errors in keying caused by noise pulses but the over-all result is far better than attempting to directly read a signal buried this far in the noise. For really solid results under very weak signal conditions a pen recorder allows reliable inte- gration of signal hits actually thin the valleys of the noise pulses.
Without signal, there should be approximate- ly 1 volt, peak to peak, of undistorted noise (measured with a wide-band scope) at the base of the reference oscillator. Attempts to increase this time-constant, or AFC filtering, will make this system a normal phase-lock affair j with attendant poor performance in ac- quiring weak signals. At the same time, any non-linearity in any part of the system. Par- ticularly before the balanced modulator will wipe out weak signals.
This system digs out the information that a signal is there— now we must teach ourselves how to use the result to efficiently communi- cate. There are several approaches being looked into, probably one of the best is toward the use of a digital sampling integrator circuit following the balanced modulator. Allen, K2UYH is working in this area with excellent
promise.
The Flying Noise Lock system is completely and dynamically unstable during no signal con- ditions. But if anything shows up in the if
passband that even is slightly coherent or that happens twice in the same way, the system locks up and narrows down. Under minimum detectable signal conditions, noise peaks kick it off but it goes right back to the signal. With- out signal, tune the BFO across the noise if on a standard receiver— this crud is just the type of information the Flying Noise Lock system lives on. Use of phase modification in- formation from a really good double-balanced phase detection circuit is something radically new, so don't knock it until you have tried it.
It is not possible, at this time, to plug in numbers prov'ng just how sensitive this Flying Noise Lock system is. I do know that it will reliably indicate signals that are buried further in the Johnson noise than anything ever seen at this QTH. The system completely ignores all types of pulse type noise just as though it wasn't there, as long as they do not saturate the rf-ff section of the receiver- It would appear this is the best presently known means of invading the never-never land of better than —200 dbm in minimum detectable signal sensitivity . Just trying to calibrate signal and noise generators at these levels is quite a job, On the air testing is slow for at —200 dbm there is no such thing as a dead band— just a morass of birdies and harmonics that are below the thresholds of any other receiver. We have succeeded in getting a firm grip on this tiger's tail— a little taming and we will be cranking 30 to 50 db improvements into communication range equations. A quick look at any of these and it is apparent why the last five years and the next is well worth any possible effort— get in and get your feet wet!
. . . K2TKN
40 mf 25 V
150^-
IN34
THRESHOLD CONTROL
1
-24 V.
FIGURE
i_
♦
T
♦
v —
L Ry
MAY 1964
11
Matching the VHF Antenna
Jim Kyle K5JKX
It's pretty well established by now that for anything at all more than low-power local ragehew purposes, feedline loss can't be tolerated at YHF. Granted it's not alwav s
4
possible of practical to use that beautiful low-loss open-wire feedline— but anybody can take care to see that the losses in his line are as small as possible*
One cause of increased loss is SWR, Al- though the additional loss imposed by SWR is usually considered unimportant unless the SWR is extremely high or the line is extremely lossy to begin with, llir extra loss is still pres- ent and often can add just enough to other loss factors to make the difference between easy copy of a "deep-fringe*" station and merely detecting his carrier in there somewhere!
And there's really little excuse for having an SWR greater than 1.001 at your favorite operating frequency. It may increase some- what as you QSY about a band, but making a proper match between antenna and feedline is so easy that the presence of detectable SWR at the chosen frequency should be cause for shame to any operator,
A couple of years ago, VHF ops had some slight excuse for the situation, because making a perfect match required a bit of ingenuity or special components. But now, there's a gadget available for $4.75 which does it all— and the excuse is gone.
This isn't just a plug for the Cushcraft CL-MS "universal matching stub/8 however, because getting a perfect match with this (or any similar) device requires a bit more thought and knowledge than were written into the factory instructions. And thafs the purpose of this article.
In case you haven't seen the gadget, it consists of a pair of aluminum rods, )k inch in
diameter and 42 inches long, spaced 1% inch center-to-center and supported at either end by a polystyrene insulating block which fastens to a modified twin-lead standoff so that the whole thing can be clamped to the antenna mast Between the insulators at each end are a movable shorting bar which can run up and down the rods, and a pair of movable terminal points (one per tube) which can also be put almost anywhere*
This amounts to a half-wavelength (at 144 Mc) parallel line of 300 ohms surge im- pedance. According to generally accepted belief, such a line can be used to match any feedline to any antenna, provided the shorting stub and feedline tap point are properly ad- justed.
However, it ain't quite that simple. If the antenna's impedance is fairly high or fairly low, the belief is correct. A point exists some- where along the line at which the resistive component of the complex standing-wave is the same as the surge impedance of your feedline, and when the feedline is moved to that point and the shorting bar adjusted to its proper location to tune out the reactive com- ponent of the standing wave then you'll have a perfect match.
But (just to take the hardest case first) what happens when the antenna's impedance just happens to be a pure resistive 300 ohm? The "matching stub" is then perfectly matched itself to the antenna, and no matter where along the stub you put the feedline tap the portion of the stub between the feedline tap and the antenna is still a matched 300-ohm line, and as such drops forever out of sight so far as offering any assistance in getting a match is concerned.
To plug in a specific example, let's say we're
12
73 MAGAZINE
Well, almost . . . the Waters Channelator ™ is one of the biggest improvements you can make in a KWM-^/l\. The Channelator has six crystal positions which can be used for transmitting, receiving, or both, or the PTO can be used for one and a crystal for the other. Instant bilateral transceiver.
Since most of us have two or three channels where we usually talk, the Channelator is ideal. With a flick of the switch we can check the net frequency and call in or just listen. In the car we don't have to carefully tune from one channel to another and don't have to retime the dial every time a leg hits the PTO knob.
Or perhaps you like to work DX. You can flip in a crystal for the transmitter, knowing that you are in the band, and go hunting with the PTO for the receiver. You can check your transmitter frequency with a switch flick at any time for QRM.
MARS members can put in two or three MARS channel crystals and flip from one channel to another with the one switch . . . mobile or at home.
The Channelator is designed to fasten to the side of the KWM in a few moments without the slightest marring of the cabinet. It takes its power from the accessory socket in the KWM (thus will operate with any KW7M power supply ) . There is one simple solder connec- tion to make ( which you can reach from the top ) and a plug to put in . . . and you're in business. The crystals for the Model 349 Chan- nelator are available from Waters for $6 each. There is a pad on each crystal which will vary it over % kc either way so you can zero in exactly on a net channel. Specify whether crystal is for USB or LSB.
The Channelator is now in stock at most ham distributors around the country. The price is only $70.9.5 i less crystals) .
The Channelator and all the other WTaters ham products are given the full treatment in the new Waters catalog. Send for one.
Waters Manufacturing, Waylcmd 73, Massachusetts
MAY 1964
13
■■
PEED
ANTENNA
MOVABLE SHORT
FIGURE I
MATCHED LINE TO ANTENNA
FIGURE 2
|
• FEED i |
> |
|
TO ANTENNA |
|
ANTENNA {MATCHED WITHOUT STUB)
LENGTH TO BRING PROPER
FEED
POINT TO FEED
STUB TO PRODUCE SWft
B EQUIVALENT
FIGURE 4
using a 52-ohiti line (without a balun) to feed an antenna which happens to be exactly 3(K) ohms, matching the stub impedance. The only place on the line we can find a resistive point at which to feed is % wave above the shorting bar (the resulting Ji-wave shorted stub effectively isn't there) and the best resistive SWR we can obtain will be 300/52 or 5.77 to 1. Not good. Toying with the stub length may reduce this a bit by putting in low resistance and fairly low reactance, but we'll find it virtually impossible to get far below 2-to~l SWR.
At this point, let's pause and look at some pictures. Figure 1 shows the general arrange- ment and factory-recommended hookup of the 'universal" stub. Figure 2 shows what happens in effect when the stub is perfectly matched to the antenna. Figure 3 is a graph showing reactance of a shorted 300-ohm line and of an open 300-ohm line (resistive components de- pend upon so many variables that no graph can be given for them*.
By plugging the values from Figure 3 into Figure 2\ effective hookup, you can readily see why the recommended arrangement cannot work whenever the stub is a perfect match to th antenna itself* If a mismatch exists between stub and antenna, then any feedline imped ant within the range Zstub/Zant to Zant/Zstub can be matched, but impedances outside this range ate also out of luck so far as matching goes*
The real sharp-eyed among our readers will have noticed by now that, from Figure 3, the reactance anywhere on a quarter- wave reson- ant line (a quarter wavelength long, one end shorted and the other end open) is always zero. At a point 1/12 wavelength up from the shorted end, for instance, the reactance look- ing toward the short will be —519 ohms (distance to short) while that looking toward the open end will be +519 ohms (distance to open) and the sum of the two is zero*
This offers a possibility of turning our gadget into a truly universal matching device; regardless of the antenna or feedline im- pedances, any one can be made equal to the value of the other plus a parallel third resist- ance, and the resistive component of this re- sonant line can offer this third resistance.
For instance, a third-resistance value of about 63 ohms would reduce our antenna re- sistance of 300 ohms down to the 52 ohms necessarr to match the feedline. And the
r
quarter-wave resonant line which results when the shorting bar of the matching device is placed exactly a quarter- wave down from the open end of the gadget offers a handy variable RF resistor.
Unfortunately, it doesn't work that way* Q of the line at 2 meters is about 2000, and when all the slide-rule work is done you come up with a tap point less than )i inch away from the short. In addition, five times as much power goes into the matching device as into the antenna; it ain't quite worth it.
But don't give up hope. There's another way. It's not quite so easy to see at first glance, but it works and works well* A full descrip- tion of exactly how it works would require pages of involved math and a few Smith charts
+ 8/5 ^
+ 625 -
20 30 *C M U TO 90 »0 fOO UO '20 HO .+0 ftO *0 sTQ
ELECTRICAL DEGREES LINE LENGTH
F1CURE 3
14
73 MAGAZINE
as well, but the general picture isn't so hard to see,
Put simply, it's this. If we can introduce a 5,77- to- 1 mismatch across a 300-ohm line, there will be a point every half-wavelength along that line at which the effective im- pedance is 52 ohms of pure resistance. All we have to do is to hook the feedline to the end of the matching device as shown in Figure 4 and we're on our way.
The problem of getting the required 5,77- to-1 SWR on a 300-ohm line which is feeding a 300-ohm antenna is a bit more involved; for this, we use the shorting stub, and this is where we have to use a Smith chart for the details (don't let that scare you away— you don't need it in practice). Assuming that we had the proper 5.77~to-l SWR on the 300- ohm line, we would find the line impedance varying from a low of 52 ohms resistive up to a high of 1,731 ohms resistive. In between, the impedance would have both a resistive and a reactive component.
Just for the example, we did use a Smith chart to find out what the reactive component would be at the first point along the line having 300 ohms of resistive component* It's a negative 600 ohms.
Now all we have to do is to supply a posi- tive 600 ohms of pure reactance at the same point to tune out the negative 6003 and we have 300 ohms of pure resistance again. Fig- ure 3 tells us that a 1422-inch (at 144 Mc) por- tion of 300-ohm shorted line will give us the reactance; fortunately, the resistive component of the line is so high that we can consider this to be pure reactance*
The Smith chart also told us how far from the 52-ohm point that 300-J600 ohm point was; the distance is 0.188 wavelengths.
So we connect up as in Figure 47 with the distance from the feedline to the antenna tap measured as 0.188 wavelengths (15-7/16" at 144 Mc) and the distance from antenna tap on down to shorting bar as another 14M inches, and the Job is done. WeVe achieved a perfect match.
The Smith chart, though, was necessary only to show an example of how this works. In practice it's much easier.
First, try the factory-recommended tech- nique. It works most of the time. But if you can't find a combination of adjustments which gets the SWR down, or if you get a low SWR only with the feedline right up near the anten- na connection and the shorting bar anywhere from % to % wavelength down from there, then antenna and feedline connections as
ERY
IGH
PI rORMANCE
COMMUNICATION ANTENNAS
BEAMS
orward Gain
ftuocrd. Lightweighr, and real pepfomerj ffoomt 1" aluminum Cubing. fl*ffltftH --** aJumrnum *Od preai- lembled on boami. Be-dd- Mo'ch for direct 52 ohm reed Add on Hading \\H o*ailab^ for dual and quad arrays-
Model A 144-1 1 — 11 element, 2 merer, boom 1 T\ . . . Model A 144-7 — 7 element, 2 merer, boom 3' Model A 2 20 II— II element, IV* meter, boom 1,5' Model AJ^O-H — 1 1 element, *& iweiet, boom 5* . . ,
$12.75
e 85
9.95 71%
& METER SEAMS full we. wide tpaced, booms I }k~ and 1 Vj~ diameter, element* *4"* diameter aluminum tubing, feddi Mouh for direct 52 ohm feed 1^1 SWR
Model a50 -3— S element. 6 meief„ boom a* ►..* $13*5
Model ASO 5 — 5 element, 6 *«#*•♦, boom 12' M . 19.50
Model A5Q d — -o element. 6 meter, boom 20/ . . , * . ... 32.50
Model A50-ID — 10 element. 6 meter, boom 24' 49,50
COLINEARS Broad Band Coverage
Ideoi oil around VKF antenna* featuring lightweight, mecha-ica! balance, high power gain, major front lobe. low SW*T low angle or fodiatron, and large capture area.
Model CL- 1 14 — 2 meter, Id element colinear .....* + + Jlo 00
Model Ct 216 — 1 '/* meter, 16 element cotinear< . . , I 2 85
Model Ch-4i6 — & meter, 16 element tolmeor. 9.B5
Model CL MS— Univeriol matching, itwb mafrhes 300 ohm 16 element
antennat to 200. 5?. Or 72 ohm leed Fines ♦ ♦,.,.»♦ 4,75
Add on ilach^ng hitt available far 32, 64, and I 26 element arrays.
TWIST Another CuthCrafl lit!
for Tracking Oscar III
For latellite tfackfng, bock matter, or paint to paint com- municalioni. Thie TwEit prgvitte* either vertical or horizontal and lefl or right circular polarisation. Ideal as a combina- tion point iq point or bote 1a vertical mobile antenna. Reddi
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Model No, A144 ?Q7 Single 20 element TWIST .......
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124.95
BIG WHEELS & HALOS 360 Coverage
©
The omoiing Big Wheel if a horizontally polarized, broad- band, omrihdifectional gain antenna. Il provide* direct 52 o"m <oa*ia< feed.
Model No. ABW I 44 Single 2 meter Big Wheel . Model No. ABW 220 Single 1 '/j meter Big Wheel Model No. ABW 430 Single % meter Big Wheel 2 Bay slacking Kitt available
■ m - « *
* * *
4 Boy flocking Kir* available ,.,,.*.. .♦- ........ .*.**..* 1 .75
MOBILE HALOS: Aluminum conitfudkm, machined hardware: Reddi Match for 52 or 72 ohm d#rect feed. 2 meter. Dual halo two bands one S2 ohm feed line.
Model AM-2M — 2 meter, with fnoit. ,.,...._„.....**<*,----
Model AM 22 — 2 meter, traded Complete . .._..,.....
Model AM-6M — 6 meter, with mati ..,,<........ • ••-*■
Model AM-26 — 6 and 2 duol halo, with mot* . —
58-70 !4.95 12.50
17,45
NEW ZIPPER PORTABLE BEAMS
6 & 2 Meters
w.f h wing nut conflructron f« ttrfdy t*t»g out povtcrb lit?, ond 7JP ascembly.
CombinaTion ZlPPf* with 5 element! on 2 meter*. 3 element* On 6 meteri Model No. A26ZP „...., ,....». JIS.PS
6 Meter 3 element ZIPPER Model No. AJO IP . . .
■* * « ■*■ ■■ ■
$10,95
SEE YOUR DISTRIBUTOR OR WRITE FOR FREE CATALOG. BUY CUSK CRAFT FOR MOIE SOLID VALUE ii PERFORMANC»
62) HAYWARD ST
rVf +
MANCHESTER N H
MAY 1964
15
shown in Figure 4.
Start with the antenna tap right up at the feedpoint and the shorting bar a quarter* wave farther on. Move the antenna tap for the lowest SWR reading you can get, then adjust the shorting bar to see if you can make it lower yet. When the shorting bar has been readjusted, try moving the antenna tap again. Getting into the right ballpark is easy; reduc-
ing the SWR from a LI reading on down to 1,01 can be tedious,
However, don't stop until you can no longer get any flicker of the SWR -meter needle at all. Then you can be sure that you have— for your favorite frequency at least— the per- fect match!
+ KoJKX
*
Where Have Our Bands Gone?
Wells Chopin W2DUD 1 1 8 Woodmancy Lone Fayetteville, N. Y.
In the beginning around the early 19Q0*s we literally picked a place to transmit on. Things were good— the longer the wave length used the better they thought the results were. You even found a few hams operating around 300 meters. Then suddenly we found ourselves relegated to 150 to 220 meters. This disturbed
l^lFtll JW- •
LICENSE NO.
\?.*
UNITED STATES OF AMERICA
F EGERAL RADIO COMMISSION
RAOIO STATION LICENSE
CLASS :
A meteor
C*U_ SIGNAL
$ 0 0 B
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DaladtftaV
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RADIO CflMMISSION.
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Fig, 1
the gang a little and work was started to get additional space for ham radio* Thus the ham bands were extended with special licenses to wave lengths from 150 meters on down. The famous trans-Atlantic experiments by hams on 100 meters stimulated interest in higher frequencies. The ARRL tests of the higher frequencies followed with the result that it was proved by hams that this new spectrum was indeed quite useful and even gave amazing
Department of Commeacs
REVISED U. S. AMATEUR REGULATIONS
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W tJ TKRRELU
16
73 MAGAZINE
think small
*
No one but Hallicrafters could shoehorn such sheer,
unadulterated talk power into so beautifully
compact a package as the new SR460 Tri-band
Transceiver, Why Hallicrafters alone? Eight
productive, successful years of SSB am) transceiver
experience, leading to such advanced, exclusive
techniques as AALC (Amplified Automatic Level
Control) providing up to 12 db, of effective
compression . . . R1T (Receiver Incremental Tuning)
with ± 3 kc; for superior net and CW operation
... and a superbly designed crystal lattice filter
which makes the most of the desirable SSB
transmission characteristics. A built-in changeover
relay permits direct operation with the HT-45 or
other linear amplifier. Sensitivity is less than 1 pv
for 20 db. (yes, 20) S + N/N ratio.
The receiver employs a separate AVC amplifier
providing a figure of merit of 100 db. These and a
dozen other outstanding features make the new
SR-160 your best transceiver buy. Write for
complete specifications or see your Hallicrafters
distributor today.
■K
Small size: 1 5" x 6'/2" x 11" Small weight: Only l3l/4 lb.
Small price: $349,50 less power supplies
and mobile mounting kit.
NEW SR-160
Tri-band SSB/CW Transceiver
Fifth & Kostner Aves. Chicago, HI. 60624
Export: Hallicrafters International Djv. Canada: Gould Sales Co., Montreal, P.Q.
FEDERAL COMMUNICATIONS
COMMISSION
RULES GOVERNING AMATEUR RADIO
OPERATORS AND STATIONS
EFFECTIVE DECEMBER 1
1938
ALLOCATION OF FREQUENCIES
152.25. Frequencies for exclusive use of 0 ma (ear stations, — The following hnnds of frequencies are allocated exclusively for up* hy amateur stations:
tscooo to fioooo kilocycle*, n 2000 to tisono kltnejcfea;*
224000 to 2&0000 kilocycles." 400000 to 401 QUO k it or y ties.
17! d to 2000 kilocycles* 8500 to 4000 kilocycles. 7O0O to T300 klloeyclci s 14000 to 144O0 k Hordes. 20000 to 30000 kilocjr-clw.
[52.26. Use of frequencies above 3GGG00 kilocycles.— The licensee of an amateur station may, eubject to change upon further order, operate amateur stations, with any type of emission Authorized for amateur stations, on any frequency above 3UOQ0O kitacyrlra without separate licenses therefor.
152.27. Frequency bands for telephony.— The following hands of frequencies are allocated for use by amateur stations using radio- telephony, typo A-3 emission :
1 BOO to 2000 kilocycle 28S00 to 300O0 HlficyclfiSt #1000 to 90000 kilocycle*,
112000 to 11 WOO kilocycles." 224000 to 230000 kilocycles." 400000 to 401000 kilocycles.
■ Bubjrri to riijfim to "HM tfl ;hJS0" MlocytlHi t» ic«irdHttrt with tl» ^flter-AiwrV cab ArrmnBwnieckt CoT^Hnf RHfliortrooiiintefliton" H**mni W3T.
■ Tto Comm tartan re«rT« tin rt*tat to chains vt caned »«• fr«m*n$1« wliliwt t4rlb#« ootlr* or bearlBl.
Fig. 3
results in daylight. This is the period when all our trouble really started. The commercial interests moved in and since that time have been consistently chopping away segments of our bands.
Many individuals have given long hours of their time and at considerable expense in campaigning to save ham radio and our bands.
If it had not been for these early hams and the ARRL we would not be here today. Over the years we have consistently lost ground. Why? Let's take a look at some of the official documents of the early period and see where we were and where we stand today. Figure 1 is 1927. It is interesting to note that in 1927 hams in foreign countries were using fre- quencies in addition to these. For instance: DX was a lot easier— you could work the Australians and New Zealanders across band on 32 to 34 meters. The South Americans were generally between 35 and 36 meters and if you preferred Europe you merely called CQ Eu- rope and looked from 42.8 to 44 meters. This was the DX man's dream— you even knew where to find the country you needed. So the over-all loss of ham bands since 1927 has been substantial. Figure 2 is a page from the FCC regulations of 1928. This is about the time when the ARRL and individual hams finally realized that we were in trouble and fighting for our life. The ARRL and individual hams did an excellent job of promoting ham radio and succeeded in slowing this trend. Analysis of the situation further, you find that since that time, what we have been really doing, is fighting a delaying action. Let's take a look at 1938 in Figure 3. Notice the chopping has begun. Figure 4 shows 1946. Figure 5 is a composite.
It's obvious unless we stop this trend of cutting back our VHF frequencies and moving us toward UHF and EHF, we will, in the near future, be talking on a beam of light and with todays technology maybe that's not such a bad idea.
It would seem, that just like all good negotia- tors, that for a change we ask for more spec- trum than we have and want, so that we have a bargaining position. Perhaps we can reverse this trend or at worst stop this nibbling away
1927
1,500
3,500
7,000
14,000
in KC
2,000
4,000
8,000
1 6,000
56,000 64,000
400,000 401,000
1,715
3,500
7,000
1 4,000
28,000
56,000
1 1 2,000
224,000
400,000
1938
2,000
4,000
7,300
14,400
30,000
60,000
1 1 8,000
230,000
401,000
1946
1,750
3,500
7,000
14,000
28,000
50,000
1 14,000
235,000
420,000
1215
MC
2300 MC
5250 MC 10,000 MC 21,000 MC
Fig. 5
2,050
4,000
7,300
14,400
29,700
54,000
148,000
240,000
450,000
1,295
2,450
5,650 10,500 22,000
1,800
3,500
7,000
14,000
21,000
28,000
50, 1 00
1 44,000
220,000
420,000
1215
2300
3500
5650
1 0,000
21,000
ABOVE
1963
2,000
4,000
7,300
14,350
21,450
29,700
54,000
147,900
225,000
450,000
MC 1,300
MC 2,450
MC 3,700
MC 5,925
MC 10,500
MC 22,000
30,000
MC MC
16
73 MACAZINE
FEDERAL COMMUNICATIONS
COMMISSION •
RULES AND REGULATIONS
(TITLE +7 TELECOMMUNICATION CHAPTER l)
PART 12
RULES GOVERNING AMATEUR RADIO SERVICE
EFFECTIVE APRIL 1, 1946
(R<rH*od to Htf % 1946)
(1) IfetouJ *fi ntt
1750 Id 2050 he. 3500 to 400(1 ko. 7000 to T3ffl> ke. HhOOOto H, 400 lie,
28 to 29,7 me. 50 to 64 infl, 144 to 148 me 1215 to IMS me, 2300 tq 2450 rat. 62JIO to 5054 me. 10,000 tfl 10,50011115. 21,000 to 22.000 mo*
(fc) Tbfl band of frequencies 420 to 450 mega- cycle* ii allocated for use by amateur uUtioiii (and temporarilj by other ncrvieea for »peeml wr navigational aids) subject to the limitation of 6G watts peak antenna power*
(c) The band of frequencies 235 to 240 meg*- ^
' cy cle« w allocated for use by amateur Italian* un til L. -
■ January 1, 1940; the frequency band 220 to 225
megacycles ia allocated for ti&c by amateur sta- tions beginning January 1, 1049-
Fig, 4
at our bands. We can prove our ranks have grown and our bands have shrunk and if that isn't argument enough I haven't seen one. Let's pull out the crying towel— history shows us to be the father of radio. Our work proved this VHF spectrum valuable. Chapping away at our bands is like killing your own father- slowly— and that just isn't cricket these days* This is the time for all of us to pull together* We need more public relations work, Our leadership must be the most intelligent we can get and in addition aggressive beyond any- thing that has ever been done before,
. . . W2DUD
FRESH UP WITH 6-UP 73'$ new VHF magazine.
$2.00 a year — send name, call, address, Don't miss it.
6-UP
Peterborough
N. H.
Connectors Mounted on Side
Connectors Mounted on Back
S$£^
Models 55GA^2 and 592 are single pole, 2 posi- tion switches with UHF-type connectors.
MODEL 550A-2
(Less Dial Plate)
MODEL 592 $735 ea.
(Includes Dial Plate)
Connectors Mounted on Side
Connectors Mounted on Back
Models 550A and 590 are single pole, 5 posi- tion switches with UHF-type connectors.
MODEL 550A $8.25 ea.
{Less Dial Plate)
MODEL 590 $8.25 ea.
(Includes Dial Plate)
Connectors Mounted on Side
Connectors Mounted on Back
MODEL 551A $7.95 ea.
(Less Dial Plate)
Models 551A and 591 are 2 pole, 2 positron special pu rpose switches with UHF type connectors. De- signed for switching any RF device in or out of series connection in coax line circuits.
MODEL 591 $7.95 ea.
(Includes Dial Plate)
PLUS A FULL LINE of single and mul- tiple-gang units with choice of "UHF", "BNC", "IM" and Phono-Type con- nectors (write for literature).
The New Switching Units shown above have the following specifications:
Power Rating: 1KW amplitude modu- lated, impedance 52-75 ohms— Fre- quency Range; Audio to 100 MC— Cross Talk; —45 db between adjacent outlets (at 30Mc) —60 db between alternate outlets.
See your local QBW) Distributor or write direct for literature
BARKER & WILLIAMSON, INC
BRISTOL, PA. • Telephone (215) 788-5581
MAY 1964
19
THE
Qua
Array for Two
Doug De Mow W8HHS 10598 Peninsula Drive Traverse City, Michigan
If I were to caunt the articles written about cubical quad antennas. I would doubtless need a small computer to get an accurate tally. Yet, this antenna is regarded with continued favoritism due to its simplicity of structure, excellent performance and for the availability of the low priced materials which go into its assembly.
Although numerous articles have been pub- lished during recent years which related to multi-element quads, nothing has been pre- sented in connection with broadside stacking of these very excellent antennas. The content of this article is the by-product of 2 years of continual experimentation with 2 meter cubical quad configurations. With the help of WSEK1 (who is currently using the array described in the text) the end result of this experimentation brought forth an antenna which has outper- formed even the best multi-element Yagis and collinear systems against which it was put into competition. The cost of this entire array is something less than $8.00. The forward gain is measured at 15.5 decibels. The front to back ratio exceeds 28 decibels and the front to side ratio is so outstanding that it was virtually im- measurable*
Although the author regards the use of coaxial cable at VHF with something more than casual disfavor, we shall describe the system with the use of a simple coaxial harness and a terminal impedance suitable for use with RG-ll/U cable. (UG!) Should the progressive VHFer desire to take advantage of low loss
balanced feedline, he will find it necessary to merely add a conventional half wave halum transformer at the feed point of the array. This will convert the unbalanced 75 ohm terminal
impedance to a balanced condition for use with 300 ohm optMi wire or low loss uhf ribbon line. In addition to the many desirable features ad- ready mentioned in this article, the completed array is exceptionally light in weight and ex* hibits very little wind resistance. It presents a fairly large aperture (capture area) which is of prime importance in receiving at vhf.
The Structure
The framework which supports the 4 three element quads is made from low priced, thin wall, electrical conduit 1" dia. material was used in the final model but there should be no reason why smaller diameter conduit could not be used. Aluminum tubing, if readily avail- able, would of course make the array much lighter.
The element supports are made from %" dowel rod (available at the local hardware or lumber store), and are either boiled in paraffin wax or weathcrproofed by coating them with exterior spar varnish. This will prevent warp- ing and deterioration caused by weather con- ditions.
The driven elements, directors and reflectors are made from ^10 copper wire which is passed through holes drilled in the outer ends of the wooden dowel rods, The tuning stubs on the reflectors are continuation of the ^10
2a
73 MAGAZINE
I5kc
!
■'.-■y-:
1
OVER THE
.54 to 31.5 mc
FREQUENCY RANGE
RXD
RECEIVER
w._£aH .iif.i
• •!■!■££>!•£
©
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W ?W\
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?CD
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£^„
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■; : : :-f
r.: :■
MV!!,I"-. ^i1'!!.1^:.--.1 J.1'!^.:.::::.^.:^:::^;;^!;,,-::
This new GPR-91RXD Communications Receiver has all of the features — selectivity, sensitivity and reliability — of our GPR-90RXD receiver.
AND IN ADDITION has 15 kc bandpass for ISB reception of four discrete voice channels or up to 64 teletypewriter chan- nels, when used with our Model SBC-2, Sideband Converter.
Two of these receivers, with common oscillators, such as TMC Model VOX-5, (see line illustration at left) make one of the finest diversity receivers available on the market today.
Our engineering department will be happy to discuss ancillary equipment in our general catalog that may be gggS&ftfe. used with this receiver to fill any of your
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Request TB 3009
m
a 5
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CORPORATION MAMARONECK, N. v.
+*^ • ■v-*- ^ v *• ■"-*■ • --•.•-•■•••----■- • .. •• • m jj.-m- ,v_ m m jm; ......;
0oA*MUNl^
and Subsidiaries OTTAWA, CANADA » ALEXANDRIA, VA. • GARLAND, TEXAS • OXNARO, CALIF. • SAN LUIS OBISPO, CALIF. • POMPANO BEACH, FLA. • LUZERN, SWITZERLAND
MAY 1964
21
wire used for the reflectors.
The metal plate located at the center of the framework, which attaches to the antenna mast with U-bolts, is made from W* steel plate.
The wooden supporting dowels for each element of the array are glued into wooden center hubs (cut from %ff plywood with a circle cutter) which are held in place on the %" conduit arms with 2 set screws as shown in the illustration. Other methods for fabrica- tion of the supporting assemblies should pre- sent themselves after examination of the illus- tration in the article. However, not being par- ticularly skilled at metal work and with mate- rials being scarce in this area, the method shown was used.
DRIVEN ELEMENT
DIRECTOR
Harnessing The individual bays are adjusted with the spacing between elements to give a terminal impedance of 75 ohms at 145 ma The 4 bays
REFLECTOR 22.5M EACH SfDE
SHORT *-
10" STUB
REF
DR.
DIR
■19-
*U-
42-
DRSVEN ELEMENT 81.0" EACH SIDE
DIRECTOR 19.5" EACH SIDE
Element data
SWR is 1:1 to 1 over 1 mc
144.5 to 145.5 with these dimensions and
spacings.
Hub detail
Material
%" clear pine or plywood
3/s" dowel rod
set screws #6 x 1 Vz"
sheet metal screws
are spaced )% wavelength apart, both vertically and horizontally, Added aperture and possibly slight additional gain could be realized by using full-wave spacing between bays. We did not exploit this possibility because of the added size of the array.
It is necessary to use 3 quarter wave match- ing transformers made from 50 ohm coaxial cable during the harness assembly. These pieces are spliced into the 75 ohm sections of line, taped with scotch electrical tape at the points of connection and then coated with epoxy resin cement to prevent moisture from entering the coax cables, RG-59/U and RG-58/ U line was used in the described model Better results would be obtained through the use of RG^ll/U and RG-8/U cables. The latter of course are somewhat more bulky. All connec- tions in the harness should be well soldered to prevent intermittent conditions and possible corrosion at some later date.
The harness cables can be held securely in place by either taping them to the supporting
73 MAGAZINE
Detroit, Michigan: MDoes an excel- lent job of swinging a 20-40 combi- nation and stacked Finco 6-2 beam/'
San Diego, California; "I am well pleased with the rotor to date, holds and turns stacked 40M and up beams in 50 mph winds with no difficulty/'
Los Angeles, California: "I have personally installed 3 other HAM-M Rotors in the past 3 years (all of them OK) so I feel that I'm buying the best."
Houston, Texas: "Wonderful! Was using the AR-22 (the CDE TV auto- matic) and it did a fine job for 4 years, but put up a larger beam and needed more power/'
Anchorage, Alaska: "Due to below- zero weather, it took quite a while
to get up but the last couple of weeks it has proved perfect. Wish I had one years ago/'
Alamor California: "Works very well and purchased on recommendation of my friend who has been using one for 4 years and likes it quite well/'
Swarthmore, Pa.: "Am very pleased with the results. More than meets my expectations/'
Pluckemin, New Jersey: "The HAM- M rotates and two TR-15's tilt the 6-foot parabola for 432 and 1296 mc."
Chicago, Illinois: "It really does the
p i
New York, N. Y.: "This is a perfect rotor. Can't see where you can im- prove it."
(a sampling of mash notes received by our HAM-M)
At $119.50 amateur net the HAM-M is the greatest rotor value around! For technical information, contact Bill Ashby K2TKN. Your local CDE Radiart Distributor has the HAM-M in stock,
CORNELL
DUBILIER
CORNELL-DUBIUER ELECTRONICS. D(V. OF FEDERAL PACIFIC ELECTRIC CCX + 118 E. JONES ST. FUQUAY SPRINGS. N, C.
CDE makes a complete line of the world's finest rotors: Ham, heavy-duty automatic, heavy-duty manual, standard-duty automatic, standard-duty manual., and the industry's only wireless remote control rotor system!
framework or using cable clamps attached to the steel supporting frame with sheet metal screws.
J2" X 12* X k/4' STEEL PLATE-*
Tune-up After Assembly
Assemble all bays in their respective posi- tions on the supporting framework, Next, at- tach a suitable length of 75 ohm coax cable temporarily to the feed point of one of the upper bays. Do not attach harness until later! Support the entire antenna structure in such a manner that the bottom 2 bays are at least a wavelength or more above ground and well away from nearby objects. A field strength meter of some type should next be placed 5 or more wavelengths directly in front of the array and preferably 2 or 3 wavelengths above ground. Use a horizontal pick-up antenna on your fs meter. Next, apply transmitter power to the feedline you have attached to the upper bay. While observing the reading on your f* meter (a buddy is handy for this), carefully adjust the shorting strap on the reflector tun- ing stub for maximum forward power as noted on the meter. Once this point has been located, solder the shorting strap in place.
Antenna support construction
Material:
4 pieces I " conduit 44" long
4 pieces 3A" conduit 36'* long
8 U-bolts for 1" conduit
2 U-bolts for 1 Vs" mast
1 I2"x 12"x 14" steel plate
MAY 1964
23
wm
DRIVEN
ELEMENT
I
DRIVEN
ELEMENT
2
fi
L,
SPLICE
T,
SPLICE
SPLICE
Ti
Jt
SPLICE
DRIVEN
ELEMENT
3
SPLICE
SPLICE
DRIVEN
ELEMENT
4
TO TRANSMITTER QUAD-QUAD ANTENNA HARNESSING ARRANGEMENT
L — 1 RG-ll/U, any length (short as pos- sible) but all L-l's must be same tength,
L — 2 RG-1 1/U, any length but both must be the same,
T— I RG-8/U, ?2%" long,
L — 3 RG-1 I/O, any length to transmitter (or through balun to 300 ohm line) .
It would be wise to adjust each individual bay in the same manner as we have just de- scribed, However, if you do not wish to be this thorough, good results can be secured by care- fully measuring the length of the timing stub from the shorting strap to the reflector, and duplicating this dimension on the other 3 bays, Next, comes the harness installation.
Details for this can be found in the illustration showing the harness assembly. A word of caution— make certain that the same polarity is observed on each driven element of each bay, when attaching the harness* In other words, make certain that all coax center con- ductors attach to the right hand terminal of the driven element and all outer shields at- tach to the left hand terminals. If you should mistakenly cross phase these bays, serious impairment of the array's performanace would result due to improper phase relationships.
Performance
There are several distinct advantages to be gained through the use of this antenna type. First, the quad-quad array exhibits a diversity
effect with regard to polarization. It responds equally well to vertical and horizontal signals. I know there will be some who will disagree with this statement, but observations over the two year period have proven this to be fact. In addition to the polarity convenience, fading on tropo work is far less than with other hori- zontally polarized arrays. This of course can be attributed to the dual polarity characteris- tics of the quad array, all of which is advan- tageous under adverse conditions. Another feature of this antenna system is its excellent back and side rejection. This is especially helpful in congested metropolitan areas where several stations are operating close in fre- quency and creating cross talk problems etc. Minor lobes are virtually non-existent. This helps in rapid pinpointing of distant signals. The antenna presents a large capture area which is particularly beneficial in receiving. (The larger the capture area, the greater the slice you take from the air and consequently the more signal you will collect on your an- tenna.)
The first model of this antenna was built and used by the author. It was built on a wooden framework. There were 4 bays but each was comprised of a 2 element quad. The elements were made of heavy duty aluminum clothes- line wire and all connections to them were made by using sal-met soldering flux, The system was in use for one year^ mounted 40 feet above ground and surrounded by nearby trees. With 25 watts of transmitter power, nightly skeds were maintained for several weeks (CW) with W8YIO who was 190 airline miles distant. Many phone and CW contacts up to 600 miles away were made with this same set-up. Though the less elaborate quad-quad array had a reduced forward gain compared to the one described in this article (12.3 db), it did a remarkable job and was taken out of service only because further ex- perimentation was desired.
By stacking 2 of these arrays, one above the other, a very effective DX antenna could result.
Without the hard work and cooperation of W8EEF, who helped develop this antenna sys- tem, this article would not be possible. We hope you will be as pleased with your quads as we are with ours,
. . . W8HHS
24
73 MAGAZINE
15 ? f.„„,A *■ SO
lively, year-round DX band stop
MIC
VALUE CHECK LIST
Compare everybody's trans- ceiver data and prices. Read all the small print.
X Y Z SB-33
|
Four bands: 80-40-20-15 |
I |
• |
||
|
Built-in AC power supply |
/ |
|||
|
Built-in speaker |
/ |
|||
|
Panel-switchable sidebands |
/ |
|||
|
Price . . complete as above |
A |
SB-33 further supports its claim to being the greatest SSB transceiver value available by offering an excit- ing fourth band, 15 meters. Sun spot minimums not withstand ing, 15 meters is frequently open for coast- to-coast and DX operation, proved this well during the recent phone DX contest by providing "pipe line" channels to South and Central America... to Europe from the East Coast.,. to JA, HI, VS1, VK and ZL from the West Coast This band is ideal for SSB transceiver operation; the major activity being in the 21.25-21.45 mc U.S. phone band thereby allow- ing all stations — DX and otherwise — to be "zeroed".
Fixed or mobile, SB-33 plays this band like a hot smash off the distant fences! The all-solid-state receiver performs in a manner that must be heard to be believed. Reminder: SB-33 is all-solid-state throughout except for the RF driver and the husky, double PL-500's in the amplifier.
For those who want the big signal at modest cost, the SB1-LA Linear Amplifier. Delivers 1 KW P.E.P. on 8040-20, 750 watts P.E.P. on 15.
.,:■:. ..: . . ...... ,,,,..,...■.,
Please send f u ft information on 3B1-LA Linear and SB-33 Transceiver.
389.50
SIDEBAND ENGINEERS
317 Roebling Rd. So. San Francisco, Calif.
NAME
t '. .; 1 1 ' 1 — i p— ^i-
NUMBER STREET
CITY
ZONE STATE
Export sales: Raytheon Company, International Sales & Services, Lexington 73. Massachusetts, U.S.A.
MAY 1964
25
Introducing a new type of audio circuit for Transistors
D Amplifier
Jim Kyle K5JKX 1236 N.E. 44th St. Oklahoma City 11, Okla,
Long-time readers of these pages will recall that from time to time we have latched onto the latest circuit developments from other countries, working on the theory that a good idea knows no national boundaries.
Well, they've done it again. Our British cousins have developed a new type of audio circuit, specifically for use with transistor which allows efficiency comparable to that you'd expect to find in a Class C rf stage!
Since it is so different from the conventional three classes of amplifiers, theyVe dubbed it "Class D" operation. Unlike the conventional three classes of amplifiers, Class D depends on power relationships rather than voltages.
Before we get into the details of just what it is and how it works, let's look at the "black box" operating characteristics of Class D amplifier. Like a conventional Class A, it draws the same total current from the supply throughout the audio cvele. However, like a Class C, the active devices inside (the output transistors, in other words) dissipate only a small percentage of the power drawn from the supply. Something like 99 percent of the power shows up at the output terminals! Input drive requirements can be as little as you like.
How all this comes is a bit complicated, though. Let's start by abandoning the concept of a transistor as being a gadget "just like a
2N255t Etc
o-
1NPUT
OUTPUT
tube only a little bit different" and look at it as another type of animal— a current-controlled switch!
If we hook up a transistor according to the schematic in Fig. 1 and leave the input terminal floating, we will find almost the fuU supply voltage present at the output term- inal. With no base current being supplied, the transistor is a pretty good approximation to an open circuit.
But if we now shove, say, one milliamp of current into the base (a flashlight cell in series with a 1500-ohm resistor is u one-mil current supply) we will find almost no voltage at all present at the output. The transistor is now biased to full conduction, and its resist- ance between collector and emitter is a small fraction of one ohm.
You can see that we are completely ignor- ing the usually used "linear*' portion of the transistor's characteristics, and operating either at cut-off or at saturation.
Now lefs look at what's happening inside the transistor so far as power consumption is concerned, when we operate in this way. The (purely hypothetical) pure curve of Fig. 2 will help to examine this.
With no base current and the "switch" open/' the collector-to-emitter voltage is vir- tually equal to the supply voltage. This is point 0 on Fig. 2* You can see that almost no current flows through the transistor, so the internal power dissipation (being equal to C-E voltage times C-E current) is vanishingly
FIGURE I
With full base current the "switch" is "closed" and current flow is limited only by the series load resistor. We have assumed for the purpose of Fig. 2 that this value is 4 ohms in our example. With a 12- volt supply, 4 ohms
26
73 MAGAZINE
NEW!
GROUND RADIAL i SYSTEM KITS
Take the work out of fabricating your antenna ground system
Here are ground radial systems for getting improved perform- ance from long-wire, vertical and other "HAIVT and "SWL,f antennas which are operated against ground. These radial sys- tems will also improve the efficiency of ungrounded antennas such as doublets, zepps and directive arrays reducing the losses resulting from ground imperfections. Excellent as permanent or temporary ("Field Day") installations. Complete, ready to roll out radial systems in two sizes to satisfy most uHAMfP and "SWLM requirements. Uses No, 14 gauge solid copper radial wires electrically and mechanically bonded to central hub. Drive pegs are provided for securing radial wire ends. Just locate center hub where you want itr roll out the radiafs and ■■■HBBnBRiSHSflHHHHHHB you're in business. Radials can be easily buried to preserve
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will allow 3 amperes to flow. The voltage from collector to emitter is almost zero; the transis- tor operates at point C. Again, however, the internal power dissipation is vamshingly small.
During the brief instants when the switch is turning on or off, the transistor operating point will shift from 0 to C along the dotted line, which is a load line for a 4 ohm resistor. The solid curved line represents a power dis- sipation of 1 watt; you can see that, while internal power dissipation is almost zero at each end of the load line, it becomes quite high during the transition periods between "on" and "off/* However, since the transistor makes the trip from 0 to C or vice versa in a matter of only a very few microseconds, this does no damage.
Fig, 2 has one more point for us— when the switch is closed we are dissipating power, but this power is used in the load resistor rather than in the transistor itself,
Now assume that we send a regular series of pulses, a perfect square wave to current, to the input terminal of our switch. We could expect to get a regular square wave out. If we placed a DC ammeter in the supply lead, we would read not 3 amps but instead VA amps of current— actually, half the time 3 amps would be flowing and the other half of
I he time the current would be zero. The volt- age, likewise, drops to half* The load resistor would be dissipating IM times 6, or 9 watts; the transistor would, as always, just be loafing along powerwise.
All of which, you may say, is very fine but what does it have to do with an audio ampli- fier, Class D or otherwise? Actually, this con- cept of the transistor as a switch is the heart of the Class D circuit. As shown in the pre- vious paragraph, the transistor just loafs along even though the load is consuming 9 watts of power. What we are talking about is 99 per- cent efficiency; all we must do now is find a way to use this trick in an audio amplifier.
To see how this is done, lets back away
4 -i
AMPERES
FIGURE 2 Switch curve,
MAY 1964
27
for a moment and consider the vacuum-tube Class B amplifier. This gadget, also, is a switching amplifier— though few of us consider it in that light. Still, only one of the two tubes works at a time. For half the cycle one tube operates and the other rests, then on the other half -cycle their roles are reversed.
This comparison provided the clue but not the complete answer. After all, the vacuum tube Class B amplifier is working as a linear amplifier when it's working, Our transistor switch is either on or offf with no in-between*
It's almost impossible to give proper credit to the inventor, since so many people in Britain are working with this basic type of circuit. But someone with a flash of genuis happened to look at the theoiy of pulse modu- lation while realizing that audio is power rather than either current or voltage alone. From there it was a simple step to the idea of pulsing our transistor switch at a supersonic rate, and varying the width of each pulse in direct proportion to the audio power present at the amplifier input.
This produces, at the output of our switch, a string of supersonic pulses whose width (and resulting individual power content) is deter- mined by the input signal To go back to our example in Fig. 2, let's assume that our square wave of current has a frequency of 50 kc. This makes the switch be on for 10 microseconds and then off for the next 10 microseconds. The total length of time for one cycle of the square wave ( on time plus off time) is 20 microseconds, The equal on and off times result in 9 watts being dissipated in the load resistor.
Now if we can vary the makeup of the square wave to make the on time longer and the off time shorter, with their total still 20 microseconds, we can change the amount of power dissipated in the load. For instance, if we lengthen the on time to 15 microseconds and cut the off time back to -5, the load will be dissipating 3 amps for % of the time and nothing for the rest of the time. Average current flow becomes 2lA amps, instead of 1M, while the voltage drop (average) rises to 9 volts from the previous 6. The power dissipa- tion has thus climbed from 9 watts (1% times 6) to 20M watts <2K times 9). If we widen the on time to 19 microseconds and thus cut the off time to only 1 microsec- ond, the average current in the load will be 19/20 times 3 amps, or 2.85 amps. At the same time, the average voltage drop across the load will be 19/20 times 12 volts, or 11.4 volts. The average power in the load under these conditions is 2,85 times 1L4, or 22.49 watts.
Similarly, we can reduce the on time and lengthen the off time to reduce the average power in the load- By now you probably have the picture, so we'll only run this calculation for the extreme 1 -microsecond -on, 19-micro- seconds off, case. Under this condition, average current in the load is 1/20 of 3? or .15 amp, while voltage is 1/20 of 12, or .6 volt Result- ing average power is 0.09 watt* Thus we can start with a perfectly square wave and produce 9 watts in the load, and by varying the pro- portions of on and off time in the wave have anything from 0,09 watt to 22.49 watts in the load circuit.
As we mentioned earlier, this square wave (we should say pulse wave, since it is square only at one operating point) is at a supersonic frequency, so we can't hear it. But if we vary the width of individual cvcles at an audio rate, the power in the load will also vary at an audio rate— and this variation in power will come through to our ears loud and clear. Our ears act as low-pass filters cutting off some- where above 10 kc, and the pulse wave itself makes no difference.
However, if you keep dogs (who can hear the 50 kc signal) or if you intend to use a Class D circuit as a modulator (we'll get into this a little later) it would be a good idea to put an additional low-pass filter at the output of the amplifier, just to make sure the pulse wave doesn't get out and cause trouble.
At this point, we have a working Class D circuit— except that we blithely said before that we varied the pulse width at an audio rate, and didn't mention how we do this. Any- thing that will give us pulse-width modulation will work, but in the interests of keeping things as simple as possible let's look at one specific hookup which is ideal for transistor use.
First, of course, we must generate our 50 kc square wave, Instead of making it square to start with, let's make it a sawtooth. Then let's feed it into a Schmitt trigger hookup set to fire at half the sawtooth peak voltage, to square it off.
The reason for doing it this way instead of making it square to start with is that we can now feed our audio wave into the Schmitt trigger at the same time and automatically vary the firing point to vary the proportions of the pulse wave. Fig, 3 shows how this works.
To start with, let's examine it with just the sawtooth present. Things always have more meaning with numbers, so let's assume that our sawtooth is 10 volts high at its peak, and the Schmitt is set to fire at 5 volts. Since we're using a 50 kc sawtooth, it will take 20 micro- seconds to climb from 0 volts to 10 volts , and
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MAY 1964
29
^PLoLTLrLrunj
^a. 1 r
LTLTLn-RJirun
I I I r T r 1 1 1 1 1 —
0 20 40 60 80 100 120 140 160 180 ZOO TIME IN MICROSECONDS
FIGURE 3
Varying the pulse wave.
then it drops back to 0 volts. In the figure, the vertical scales are all in voltage while the hori- zontal scale is in time.
As the sawtooth starts from 0, the Schmitt sits at 0 input and its output is similarly 0. (The Schmitt, in case you didn't recognize it, is nothing but a pair of switches hooked up so that each one turns the other one off.) After 10 microseconds, the sawtooth voltage has risen to 5 and the Schmitt turns on, bringing its output voltage up to the supply-voltage level. As time passes, the sawtooth keeps rising but since the Schmitt is already turned on it makes no difference. At 20 microseconds, the sawtooth falls to zero and as it passes through 5 volts on the way down, the Schmitt turns off and its output drops to zero also, From here, the cycle repeats. You can see that the Schmitt is on for 10 microseconds and then off for the next 10, and so forth.
Now let's see what happens when we add a 5 kc sine wave to the input. Just to make it simple, let's make this wave the same peak-to-peak voltage as our sawtooth, or 10 volts.
Starting as the sine wave crosses the zero point, the input to the Schmitt will also be zero since the sum of the sine and sawtooth waves is zero. The sine wave is rising toward its 5 volt positive peak at the rate of 0.14695 volts per microsecond at this point (the first 10
£00 K
■vw
lOmf
AUDIO
>IO INPUT I/..
Vt P-P \\T
TO CLASS C STAGE
FIGURE 4
Experimental 70 watt class D modulator. Modulator transformer: primary to handle 3 amps, 4 ohms dc resistance (each half) — secondary to suit. Either side of supply may
be grounded, Adjust value of 10 K resistor for square wave at bases of 2N277's with no audio. Adjust 390 mmfd capacitor if necessary for 50 kc square wave frequency.
30
73 MAGAZINE
microseconds represent 18 degrees, and the voltage at the end of this time would be 5 times sin 18, so the rate in volts per micro- second is 1/10 of this or 0.14695) while the sawtooth is climbing at & volt per microsecond. At any given time the Schmitt input voltage is the sum of these two, so that we can add the two rates together and divide into 5 to find out when the combined wave will reach 5 volts and turn the Schmitt on. The more-or- less exact time when this happens is 7.72859 microseconds after the zero point*
From this 7% (approximately) microsecond point the Schmitt remains on until turned off when the sawtooth falls back to zero at 20 microseconds. For this cycle of pulse wave, the off time was 7% mircoseconds while the on time was 12K microseconds.
Starting point for the next cycle finds the sine wave at 2.389 volts (it is 36 degrees from zero, so the voltage is 5 times sin 36) while the sawrtooth is at zero. Going through the same procedure of determining the rise rates, we find that the sum of the two waves will pass through the 5 volt point 4.03586 micro- seconds later and turn the Schmitt on, where it will remain until the sawtooth next falls to zero.
So during this second cycle of pulse wave, the off time fell to 4 1/32 microseconds while the on time rose to 15 31/32 microseconds.
We won't go all the way through the cycle this way since the figures get extremely com- plicated near the peaks of the sine wave and you undoubtedly see how it works by this point. On the negative going half -cycles of audio it works the same way except that, since the sign of the audio voltage is reversed, the difference between the two waveforms rather than their sums determines when the Schmitt fires. Thus the off time will increase while the on time decreases.
At this point someone is sure to ask "Why not use the Schmitt itself as the output stage? It's a switch, you said.'* And the answer is that it can be used if you want to keep things as simple as possible.
However, the real beauty of this type of amplification over all the more-conventional classes is that, once you have converted the audio to a modulated pulse train, you can boost it on up to any level you want with a series o£ switches! A typical Schmitt, designed for fastest possible switching (we have to keep that transition time short, remember, to stay out of the high-power-dissipation regions with our power transistors) will switch maybe 5 watts on and off. It can control a switch which is handling 500 watts! This one, in turn, can
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control a 50 kilowatt switch* And so forth. For an extremely low-power amplifier. Class D is hardly worth the trouble of putting together the pulse modulator. But for moderate or high power, it drastically simplifies the circuitry.
Now that we've gone through the Class D amplifier to see how it works, you'll probably want some practical how-to-build-it informa- tion. As this is written there has been no op- portunity to build and de-bug a circuit, but the design of Fig. 4 is offered as a starting point for any interested experimenter.
The eagle-eyed among you will note several differences between Fig. 4 and the example circuits mentioned earlier. The most obvious, and the most major, is that it uses push-pull switches driven from the two halves of the Schmitt, instead of a single switch.
Using switches in push-pull as shown here doesn't have all the advantages associated with tubes in push-pull, but does have one great advantage— current through the total trans- former primary will always be the same. When one switch is on, the other is off, so current in one side will be maximum when the other side is minimum. But averaged over an audio cycle, the average current in both sides is equal; it also happens to be equal to the no-signal current, giving the circuit its similarity to a Class A circuit in this respect.
Xo low-pass filter is shown, although the circuit is intended as a modulator. This is due to the transformer used, a common 115 volt filament job. A transformer of this type is a pretty good low-pass filter in itself, at 50 kc* Should any 50 kc energy get out and give you spurious sidebands at 50 kc intervals from your carrier frequency, add an rf choke be- tween modulator and final, with a capacitor to ground large enough to bypass the 50 kc widiout hurting your 3 kc audio limit
Audio input level isn't especially critical, but it should not be allowed to exceed the peak level of the sawtooth (which in this circuit is about 10 volts). If it does, you'll get a clipping effect since the sawtooth voltage is used to turn the switches off every cycle!
For additional data on this type of circuit, try the writings of D. R. Birt and K. C. John- son in Wireless World. In addition, an article by George F. Cooper in the June 1963 issue of Audio (published by Radio Magazines* Inc., Mineola, N. Y.) discusses the circuit as it ap- plies to high-fidelity amplifier design. For other approaches to trigger circuits and tran- sistor switch design, try the G-E Transistor Manual and Howard W, Sams* Transistor Cir- cuit Manual by Allan LyteL But for the best information on the subject, try it yourself!
, , . K5JKX
12
f
rom
6
Vladimir Gercke K6BIJ Box 143 Weimar, CoL
Dynamotors in a mobile operation are things of the past. With their 30% efficiency, com- mutator arcing and mechanical inertia, they cannot compete with transistorized power supplies.
However only a 30-40 watt rig can be operated from a 6 volt battery. It is possible to build a higher power transistorized supply, but buying a 12 volt car is cheaper.
The following two circuits designed to pro- vide 12 volts from a 6 volt car system were built and tested. Both require no changes in your present electrical system other than in- serting one resistor,
In the first one (Fig. 1) the value of resistor Rl is chosen so that a voltage drop across it is 6 volts with charging current to the battery held constant and reduced about 50%. This will
make available 12 volts at the "A?s terminal of the generator. A typical case with a 30 amp generator will look like this: the generator is producing its normal 30 amps, but the voltage at "A" is now 12 volts instead of normal 8 be- cause the field coil has 12v/3 amps across it instead of usual 8v/2 amps. The 12 volt out- put is split in two equal parts— 15 amp is avail- able for your 12 volt load ( 180 watts) , and the other 15 amps are dropped by Rl to 6 volts and are used to charge the battery. Your volt- age regulator MAX current contacts are ad- justed to open at 15 amps instead of 30, and their action will keep the generator output constant at various engine speeds,
It is recognized that this method puts 50% overload on the generator, but if your engine does not overheat and you do not drive through
32
73 MAGAZINE
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"I I
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f
MAY 1964
33
E V. LOAD g o
KNFE SWITCH
'~1
6 V GENERATOR
JT
n, -
6 V
15 AMPERE
._ >- ■ 0 4 "
□_
£
s v
BATT£>T
VOLTAGE REGULATOR
FIGURE I
2000 mf
l£ V LOAD
D tt
6 V. BATTERY
FIGURE £
See TRIAD brochure TY-61 for components not shown here.
the desert, it seems to be perfectly safe. When 12 volts are not needed, switch SW is closed and the system returns to normal, except that the maximum charging current is now 15 amps (10 ohms across "F" and GND on your regulator will restore it to 30 if necessary),
A word of caution— open Rl will result in a burned out generator, better use a 150-200 watt resistor.
Second circuit (Fig. 2) makes use of an ordinary transistorized dc to dc converter. Both input and output are 6 volts, the output
is simply connected in series with the car battery providing 12 volt output for the load.
No transformers are available commercially but they can be easily wound at home. No calculations are necessary— you just pick up any 100 watt 60 cycle transformer that has a 6 volt winding on it and remove all wire, counting the number of turns on the six volt winding only. Using the heaviest wire pos- sible, wind two identical centertapped wind- ings using the same number of turns each side of centertap as the original 6 volt winding had. These windings will be II and L2< L3 is same as L2/L3, but uses thin wire about 28 to 30 gauge,
"B" is a 12 volt light bulb. It serves as a bleeder passing about one ampere and doubles as an indicating light showing the presence of
an output.
The 6 volt, 12 amp output (72 watts) in series with your car battery will provide 140 watts of 12 volts output to the load. "S" are silicon stud rectifiers rated 50 PIV at 15 or more amps. Do not use selenium units as the voltage drop across them is too high. Tran- sistors are the same as you would use for a regular 6 volt transistorized power supply delivering the same wattage output. Triad brochure TY-61 will help you select them as well as other component values for your cir- cuit.
The same ideas can be used to get 24 volts out of a 12 volt car electrical plant.
. . . K6BIJ
A Single Tube Oscillator-Multiplier
Jim Kyle K5JKX 1236 N.E. 44th St. Oklahoma City, Okla.
Need something small yet reliable to provide a crystal-controlled signal at 200 mc or below?
Here's a single-tube circuit which can do the trick, yet is equally useful at 1800 kc if your interests run to low-band work. And the single-tube description doesn't resort to tricks like the Compactrons to do it, either. We're talking about just one little pentode. If you use a triode-pentode or the like, you can move the upper frequency limit out to 600
mc at least!
The schematic may look a bit odd at first, but here's what we have; Forgetting the sup- pressor and plate and considering only the cathode, grid, and screen, we find a conven- tional Miller crystal oscillator. This circuit works with either fundamental or overtone rocks, and will give good output as high as 50 mc or more with third-overtone crystals.
Now let's move on to the plate, By using
34
73 MAGAZINE
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electron coupling, we have separated the crys- tal and plate circuits sufficiently that the plate tank may run straight through, double, triple, or even quadruple. And by using a 50 mc overtone rock to start, then quadrupling in the plate circuit, we come out at 200 mc from the single tube.
For some examples of the circuit's usefulness, a 6U8's pentode half can be used with a 45.667 mc crystal to get 137-mc output from the tripling plate circuit; this will be adequate to run a 144 mc to 7 mc converter, leaving the triode half of the tube free to use as a mixer*
Again, a 6AG7 or 6CL6 can provide 48 mc or 50 mc output, from 24 or 25 mc overtone rocks and doubling in the plate. With this circuit a 2-tube 90-watt 6-meter CVV rig could easily be built.
At lower frequencies, a 2-band CW rig could be designed around 7 mc rocks, a multiband tuner in the plate, and a pi-net output Very little more would be needed to make it operate on 40, 20, and 15, and 10-meter use would not be impossible, Suitable tubes would be a 6CL6 and a 6DQ5, and input could run up to 120 watts or more. How about this for portable operation?
Some of the less-obvious advantages offered include easy crystal switching, since one side of the rock is grounded, and almost perfect isola- tion of the load at all frequencies so long as screen voltage is kept low enough so that the plate doesn't swing below the screen.
Let's be fair; this circuit didn*t originate here, It came from Ed Steinberg, and was originally published in Electronic Design maga- zine. However, Electronic Design is an engi- neering-level publication with circulation re- stricted to professional engineers, and this cir- cuit is just too good not to pass on. Have fun with it!
OUTPUT
!_! resonates at xtal freq.
L0 resonates at desired harmonic
SCR B+ should be regulated
MAY 1964
35
More About
SSB, DSB, AM, etc
Thomas Prouty K6HJH MHD Research, Inc. Newport Beach, California
The battle started in the early 50s when hamclom divided against itself over "SSSC" (which was too much of a tongue twister to survive)* John Costas made matters worse in 1956 when he added DSB as ground for fur- ther subdivision, I've followed this thing through the pages of LR.E, (including the Professional Group on Communications Sys- tems), Electronics, CQ, QST, 73, and heard it discussed in every other gathering of hams for about 10 years. It has grown out of all proportion and left men without the use of their reason— much like racial prejudice. I am finally compelled to have my say. Congratula- tions, W3AQT: you finally got to me (April issue, p 17),
The Ground Rules
There are generally two basic types of peo- ple who argue modulation systems. They are: those who understand and enjoy the mathema- tics of communications systems and those who understand a faint voice running 2 watts 3000 miles awav but wouldn't know a Bessel func-
■
Hon if they tripped over it. Most hams fall somewhere in between.
Since each group uses different approaches, they have divided the whole mess into two distinct battles, each with two sides. Most of the present confusion comes from trying to settle the matter once and for all in so general a way that it answers the problems of both groups. It cannot be done.
Since this is being written for ham consump- tion, we can leave out the jazz that goes into a systems study for NASA or the Signal Corps and consider only the particular problems that a ham might have. In articles written for the engineering profession, such things as input power, weight, cost, or reliability might be suitable criteria. Of these, cost is perhaps the only one which would also apply here, and more will be said later on this point although no numerical comparisons will be attempted.
So from here on, this discussion will be con- cerned with voice (not sine wave) transmis- sion, using a transmitter whose average power input to the final amplifier stage is limited to 1 kw. Just to keep things simple, it will be assumed that only the final amplifier con- tributes power to the antenna although more about this point later on. We will consider the fact that since a ham does not have control over both ends of the transmission circuit, he must determine the results of operation be- tween his transmitter and the various types of receivers with which he may come in contact (If you ever tried to operate wide band FM in the old days, you know what I mean.)
Finally, a word of warning— if you read the high brow magazines, make sure that argu- ments presented there are based on the same sort of comparisons that are important to you,
Power
One of the first things that must be con- sidered is just what contributes to the ability of a communications system to transmit intel- ligence. At the receiver, the important thing is the signal-to-noise ratio, that is, the amount by which the signal exceeds the noise. Nowadays, nearly everyone is familiar with the concept of signal-to-noise ratio when used at the receiver but this involves a knowledge of the propaga- tion losses, antenna gains (or losses), etc. If we used the concept of signal-to-noise ratio as it exists at the transmitter, we have in effect the same concept without the propagation and antenna considerations. Granted, the actual number of signal-to-noise ratio at this point might seem astronomically large, but if we Further refine the concept by eliminating the temperature and Mr. Boltzmann's constant, we come to the concept of intelligence power per cycle of bandwidth. This is the real way to compare modulation techniques.
Many discussions on this subject bog down over a peak vs. average power argument. You
36
73 MAGAZINE
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MAY 1964
37
have all heard the ^2 kw peak envelope power** bit for SSB. Have you ever seen an AM envelope on a scope? Have you noticed that with 1002 modulation the peak voltage is twice the unmodulated voltage? Since power is proportional to the square of the voltage, then it would seem that the peak envelope power for AM is 4 kw. Of this, 2 kw is in the peak carrier and 1 kw is in each peak sideband. So what! People don't talk in peaks but in a whole series of sounds having varying degrees of loudness. By clipping we can suppress the peaks and have a high average level This is what must compete with the average noise power at the receiver.
Here's a New One for You
If you are still skeptical, let me simplily by giving an example. Consider a pulse code modulation system in which speech, having a spectrum lying between 300 and 3,000 eps, is sampled at a rate of 2 samples per cycle or more. The sampling rate must then be 6 kc/s or higher; let's stop at 6. Since we want to exceed the noise at the receiver with these pulses we will keep them at their maximum value at all times. Therefore, we will avoid pulse amplitude modulation (PAM) and use either pulse width modulation (PWM) or pulse position modulation (PPM). See Fig, 1 for a diagrammatic explanation of these modul- ation systems.
If we use PPM* all o£ the pulses are alike. If we use PWM the width will be varied above and below an average value. Since the modula- tion frequency does not go down to dc, we can assume the average value in our power cal- ^illations. Let's start the fun by assuming a 1 microsecond pulse width. With 1 microsecond pulses transmitted at a 6 kc/s rate, we have a
MODULATING WAVEFORM
PULSE WIDTH MODULATION
DELAY *
pi
PULSE POSITION MODULATION
FIGURE )
duty cycle of only 0,6%. This means, that for an average power of 1 kwT we can use a peak power of 167 kw. , >'!!
Before you go out and buy some big bottles, read on. The receiver must have a much higher bandwidth to handle this kind of a signal and therefore, its noise input will be higher. If we use a pulse which has a roughly triangular waveform, the receiver may have the minimum bandwidth. As the pulse gets wider, the receiver bandwidth may get nar- rower, so that as the peak pulse power goes down, so does the noise power at the receiver input. The sad truth is that for any practical combination of peak power, pulse width, and bandwidth, the power density which we may reach with this system is about 0.25 watts per cycle of bandwidth. Since this number may not mean much we shall develop similar num- bers for AM, SSB, and DSB and see how they compare. But as you read, remember, if peak power would do the job, the whole world would be using pulse code communications. (Actually, a good portion of it is but for different reasons. A discussion of this subject is interesting but too involved to include here-)
Good Otd AM
Let's look at AM for a minute, For 1 kw of carrier power we can put 500 watts in the modulation if we use sine wave modulation. But people don't talk in sine waves so the situation is somewhat different. Speech differs from a sine wave in the way in which its intensity fluctuates. Thus it is impossible to keep the level of modulation at or near the peak value without clipping.
What about clipping? Clipping helps in speech communications systems because all Systems are limited bv the hardware to the peak power which they may handle. By clip- ping, which we may also look upon as in- stantaneous AGC, we are merely smoothing out the peaks and valleys in our speech in- tensity profiles and enabling our transmitters to operate nearer their peak output for a greater percentage of the time. We are there- fore, increasing the amount of the time when our signal will exceed the noise at some remote receiver* Clipping can be used to varying degrees with different types of com- munciations svstems. With AM, ver\ heavv clipping can be used. Even infinite clipping, or square wave modulation, is feasible and if you hide in one of the corners of some remote UHF band you can use such techniques; the splatter will keep you off the lower bands.
Just to give AM a real boost, let's assume
as
73 MAGAZINE
rfnatfen, QUALITY MADE COMPACT ANTENNA
that we are using 100 percent clipping, or square speech waves* Now, instead of having 500 watts of audio packed onto our carrier, we have 1 k\v\ This divies up as follows: 1 kw in the carrier, and 500 watts in each of two sidebands. If we use both sidebands in the receiver ? we have 1 kw of intelligence power (the carrier contributes no intelligence) spread over 6 kc/s or 0.167 watts per cycle* If the receiver has a 3 kc/s bandwidth and only uses one sideband, we have 500 watts spread over 3 kc/s or the same 0,167 watts per cvcle. Without clipping, the power density is cut in half since we can no longer put as much power in the sidebands. Also, since the speech in- tensity will vary and we are limited to a peak intensity of 500 watts, the actual power density which we can achieve in practice is even less than half. Since "how much less*' be- comes a difficult question, let's just avoid it by assuming half. Then we can use 0.083 watts per cycle for AM with no clipping.
SSB
With SSB and an average input to the final of 1 kw then we will have just 1 kw of power to play with and if we are lucky, it will appear in just one sideband. (We will consider effi- ciency later). It doesn't matter whether clip- ping is used or not because it doesn't effect the average power one way or the other. With AM the power in the carrier is limited and we are trying to pack as much sideband power onto that carrier as we can. So we clip the speech to raise the average power that we can use without over-modulating. With SSB we have no carrier so we don't have the same problem. In fact, the only reason to consider clipping in the SSB case is that it might reduce the peak power demand on our linear amplifier.
Clipping must be used carefully with an SSB transmitter, however, since heavy clipping can actually increase the peak power demand on the final Moderate clipping and filtering can be used successfully and if a high pass filter having a 6 db per octave roll off below about 800 cps is used ahead of the clipper with a low pass filter having a steep roll oft above 2750 cps alter the clipper, heavy clipping will give good results.
At any rate, clipping wont help us any here so we come back to 1 kw spread over 3 kc/s of bandwidth which gives a spectral power density of 0.33 watts per cycle.
DSB In a recent article by W3PHL (73 Magazine, February 1963) quite a bit was said about the way in which the power should be delivered
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MAY 1964
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to a DSB final and the way in which it should be measured. Just to set the record straight, the conclusion which described a DSB final that packed in 1800 watts of average power is just not consistent with the legal limit of 1 kw. It doesn't matter what kind of complex logic you employ to get to a conclusion, a watt is still a watt and if RMS sensing meters having 0.2p5 second time constants are used to measure the volts and amps, then the result will be true power input (thermal equivalent) to the final on the same basis as it is in the case of an SSB final.
So with 1 kw of input to the final we will have I kw divided between the two sidebands* Again clipping does us no good since there is no carrier to consider and the effect on the size of the final amplifier is the only consideration that might make clipping worth while. The spectral power density is 1 kw over 6 kc/s or 0,167 watts per cycle.
What's the verdict? So far the spectral power densities look like tli's:
AM (no clipping)
AM (100% clipping)
SSB
DSB
PWM or PPM
AM (no clipping)
0.083 watts per cycle 0.167 0.333 0,167 0.25 0.0624 watts per cycle
//
tt
* *
ts
it
it
tt
Efficiency W3PHL assumed 75% for a class C amplifier and 602 for a linear, These figures are probably representative of the best current practice so let's keep them. Then the table shown above should be modified as follows (assuming DSB to use a high level modulator):
AM (no clipping) 0.0624 watts per cycle
AM (100% clipping) 0,125
SSB 0,18
DSB 0.125
PWM or PPM 0,1875
Look who wins nowI (I wonder what kind of a fight this will start*)
Receivers
For reasons to be explained later, let's examine the whole situation for several different types of receivers. The most important practical cases would include bandwidths of 3T 6, and 15 kc, plus synchronous receivers. Since a synchronous receiver is already pretty complex, let's assume that it has a number of "square" filters which the operator can select for opti- mum reception of any given signal. Also, I like to give phase coherent receivers an ad- vantage in signal-to-noise performance of 1.414 instead of 2 as is often quoted for them.
Watts per cycle of receiver bandwidth System Receiver
3 kc/s 6 kc/s 1 5 kc/s Sync AM (no
clipping) 0.0624 0.0624 0,025 0.0882
AM (100%
clipping) 0.125 0.125 0.06 0.176
SSB 0.18 0.09 0.036 0.18
DSB 0,125 0.125 0,06 0.176
PWM or PPM 0.093 0.187 0.075 0,264 Note: The pulse width used with PWM or PPM has been assumed to have been optimized for 6 kc/s receiver bandwidth to show the effects of non-optimum receivers on system performance. The pulse width could easily be changed to suit other receivers.
Conclusions No one should be caught dead without speech clipping on his AM transmitter. If you can afford one, you should have a synchronous receiver. From there on, it is up to you. There really isn't much difference. Just remember that some judicious filtering will be required if you want to use PWM, PPM, or heavy clipping without splatter.
Discussion
OK, you say, so all this jazz is fine but what makes the SSB signals get out when the AM Signals don't? I think the answer to this is not to be found in the science of radio but in the practice of it First, SSB is more com- plicated and therefore has been practiced more by the better educated and equipped ham, or by the ham who chooses to buy his rig. So the transmitter is probably a little better. Second, SSB addicts found long ago that that stability requirements forced them to pretty good receivers and this produced a sizable improve- ment all on its own. Thirdly, there is the sub- jective factor of not having all those heterdynes. Fourth, the convenience of VOX operation make the whole thing more enjoyable. These factors plus the "real" improvement due to SSB account for what happens— I think.
Now for the practical approach, Most of the preceding junk assumes that you have plenty of money; the whole band to yourself, and control over both ends of the circuit. But it is just not so in hue life, Most hams have some purpose in their hobby. If operating is the one that interests them, they must operate with some other ham or hams. So each one has got to pick his intended receivers- If you like to talk to the SSB crowd, don't go on AM— you won't make it. If DX is vour real aim in life, why not brush up on your code? (111 bet you thought we would overlook CW altogether —didn't you?} If new things interest you, try DSB and consider building a synchronous receiver— I am.
40
75 MAGAZINE
SERVICE
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MAY 1964
41
That probably didn't satisfy many of you, Let's consider a different tack. You don't have a key to Ft. Knox so the cost per watt is irn portant.
The grounded grid linear amplifier deserves special mention here. Its simplicity, low cost, and the fact that it can be "over 100% efficient'' (remember that drive power also contributes to the output) make a strong case for transmit- ters based on this. Also the high price of high level plate modulators should be considered. These facts, coupled with the 50% duty cycle of average speech and the effect this can have on power supply requirements makes a very compelling case for SSB and DSB. Stated another way, the average ham has a better chance of getting the legal limit if he uses the lower cost SSB and DSB systems than if he uses AM. If he doesn't want a big voice but can be happy with 10 watts, then the picture changes and AM looks good. Don't ask me where the cross-over occurs!
Consider who you leave out though when you plan your system. Nearly everyone is now familiar with SSB tuning and nearly any reasonable receiver will do* Those with receivers that have at least one steep side to their passband can copy DSB, some won't even know that the other sideband is there. But those with wide conventional receivers can't copy DSB at all.
To summarize it all up, let's make some simple statements:
1) If you use AM, use plenty of clipping and filtering,
2) If you can afford it, buy or build a synchronous receiver.
3) Choose a system to suit your tastes, the mode your friends useT or the amount of money you have. There is scarcely 6 db between the worst and the best and a Httle time spent on your antenna will nearly always be more rewarding at less cost.
4) If "maximum effectiveness" really bugs you remember that the only reason we didn't include a big discussion of CW here is be- cause it would shame everyone out of the place —you can pack in 5 watts per cycle without even starting to get fancy and at less cost than any other system.
5) Please forget all about PWM and PPM. They are hard to put to practice and the splatter problem is fierce. And think of the arguments this would start.
6) One of the things that keeps our hobby so active is the fact with all the scientific methods at our disposal, there are still no 4 right" answers to all problems and everyone can develop, practice, and talk about his own opinions and ideas.
. . . K6HJH
An Inboard Calibrator for the NCX-3
Many hours spent reading the myriad brochures on tranceivers resulted in the pur- chase of a beautiful new NCX-3. After careful unpacking and a brief inspection of the instruc- tion book, I I looked everything up and put out a CQ on the low end of 75, "Get back in the phone band," said a voice, "But I am in the phone band/' said L "You are two kc out," replied the voice. Sulking, I tuned up on CW down in the Novice band and got a calibration check from a friendly novice who was all too pleased to tell me his crystal freq. For the time being at least, I was calibrated* As much as I hated to face it I needed a calibrator. My checkbook was still recovering from the shock of almost $600,00 spent on the NCX-3, power supplies and other accessories; so it was no
George Morton WB2MAH ex W4HUP
Pbom by A. J. Spatafor* WB2FGL
surprise that another $27*00 wasn't readily on tap. Besides, I didn't like the idea of anything sticking out of the rig when I put it in the mobile. I would have to make a calibrator and then I could mount it inside the NCX-3.
National engineers used the shoehorn treat- ment to squeeze all those components into that little box, so there seemed to be no room for a calibrator— or any thing else. Consultation with my good friend, Jack Daniels, produced the opinion that normal mounting was out of the question. I guess this is the conclusion that National's boys came to or else they wouldn't have made provision for mounting one out- board.
Looking the problem over in a new light I found there was enough room for a small
42
73 MAGAZINE
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I I I I I I I
chassis behind the meter. If the tube and crystal were installed horizontally instead of vertically there was more than sufficient space there. Digging through the junk box I managed to come up with all the parts except the cry- stal, I even had a piece of aluminum that could be cut to make a chassis. A caU to one of the locals resulted in a swap of a pair of 6L6s for a cr
nal strip (3 term & ground), and the grommet The type of trimmer you use for CI will deter- mine what size hole(s) you will need there. Mount CI. Run a small piece of bare wire
Chassis Construction Cut a piece of aluminum to 6"x2'\ Cut small notches 1% from each end on both sides, make these notches &" deep as shown in Fig. 2, Cut in XA" from all corners, drill holes referring to Fig, 2, Holes for mounting the crystal socket are under 2, the grommet hole under 2, space for mounting C 1 under 3, 4 is the tube socket cutout and 5 is the hole used to mount the terminal strip.
Bend the aluminum on the dotted lines as shown on the template, to form a chassis. Look at Photo #2 and you will see that there is a quarter inch lip all around, the lip on each end of the chasis as shown should be bent the opposite way so you will have surface to mount the calibrator in the NCX-3.
Wiring Mount the tube socket, crystal socket, termi-
Just tike in the soles brochures except some- thing has been added behind the meter. Wiring from the calibrator can be seen run- ning to the large hole under the meter for internal connections.
MAY 1964
43
Mounting detail showing chassis placement. Change in position of crystal and tube in new Installations (see text) is suggested.
The calibrator fits in perfect ly, be careful not to hit those coils just to the left of the calibrator.
from one of the terminals on CI through one of the pins of xtal socket and to the ground lug on the terminal ship. Ground pins 2, 4 and 7 of the tube socket to the ground lug terminal Mount C4 (10 mmfd) from pin 5 of the tube socket to one of the terminals on the strip, R3 goes between two of the terminals on
FILAMENT
CALIBRATOR SOCKET ON REAR OF MCX-3
6AK6
100 Kc CRYSTAL
220V
PART OF Rw MICROPHONE GAIN CONTROL
the strip. Finish wiring as per diagram Fig* 1, Solder a piece of #18 hookup wire 24" long to pin 3 of the tube socket. Three more 24" lengths are soldered to the terminals of the terminal strip; the ground lug, the B+ end of R3 and the output side of C4. These go through the grommet Parts values and layout is not critical as long as reasonable tolerances are considered. LI should be mounted in such a manner that it is equidistant from all ground points for maxim tun output.
Installation Not wanting to drill holes or otherwise foul up my new pride and joy, It was decided that a new means of mounting the sub-chassis would be needed. Glue was the answer. Yes, glue! Not model glue, but that expensive Eh> pont stuff guaranteed to hold two boards together so well that wild horses couldn't pull them apart. Thirty five cents will buy about 100 times what you wiU need to do the job, so maybe you can borrow some from a neighbor.
FIGURE J
Under chassis wiring of the calibrator fol- lows the wire harness (white arrows), the ground lead is connected to ground terminal next to hole in upper LH corner.
Apply a thin coat of glue to the areas to be joined and then press firmly into place as shown in the photos, with this exception; the tube should be on top and the crystal flu bottom. This will protect the crystal from excess heat in your installation. I have had no adverse effects but if I had it to do over again I would do it the other way- Besides if you mounted it like I did you will have the grommet and wires feeding through it away from the chassis if you followed Fig. 2. The template was drawn with this revision in mind. Don't worry about the ability of the glue to do the job. I have had this rig in and out of the mobile and fixed set-up for three months now and it is as sturdy as ever. I haven't had a chance to get any wild horses yet, so I will make no promises on that account. The only problem with the glue is in getting an effective
44
73 MAGAZINE
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I I
1
MAY 1964
45
t
4
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5
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I
1-1/2
z-wtr
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FIGURE 2
de ground. This is why we ran a ware from the ground lug of the terminal strip.
After giving the glue time to set, ran the wires from the grommet through the hole under meter. The photos will give you an idea of how it is done. Connect the ground lead to the ground lug on the first terminal strip you come to under there. Run the others to- wand the back of the chassis following the wire harness to the calibrator socket at the rear of the NCX-3. The little white arrows in the ihoto shows the way. The calibrator output ead goes to pin -4 of the socket the filament connection to pin #7 and the B - lead to pin 8.
Push-to-Talk
for the HT-37
Rolf Carlson W2ZBS
When the background noises in the shack get Unusually loud (two small harmonics run- ning around), the author on occasion has wished for a push to talk circuit in his HT-37 for more positive control over the station's operation! Anyone who has used voice control (VOX) knows its susceptibility to sounds other than the operator's voice. In looking over the circuit diagram, it was obvious that a push to talk modification for this transmitter could be accomplished in several ways. However, the author desired a) the simplest and easiest modification, and b) no changes to the normal
V \5B
./2-t2AT7
Rt'Oy Tube
To MOX Actuate
Relay
Added W«re
Ptione jack Added On Rear Of Chots=i
FIGURE I
Plug in the tube and crystal, turn on the power and you are ready to try it out. Allow a few minutes for things to cook a little, then pull the mic gain control out, this will apply B+ to the calibrator (a switch is part of this control for exactly this purpose). You should find a strong signal near one of the 100 kc dial divisions, Eureka, it works!
To zero the calibrator it is necessary to use a receiver capable of tuning \VWV or a local BC station that operates on a multiple of 100 kc. Run a short length of wire from pin #4 of the calibrator socket in the XCX-3 to the antenna input of die other receiver. Zero beat and you are set. Be careful if you use ac/dc set and a BC station as your standard, you could get quite a charge out of the calibration. Alter zero beating your reference sig, button it up and you are in business, safe from fear of an FCC QSL.
. . . WB2MAH
Parts needed in addition to those shown in Fig, 1 :
2x6 inch piece of aluminum for chassis
seven pin miniature tube socket
three terminal and ground terminal strip
crystal socket
Miscellaneous mounting hardware
operation or appearance of the transmitter
The modification to be described here re- quires installing a phone jack and a piece of hookup wire soldered between the phone jack and a terminal strip in the VOX circuitry. That's about as simple a change that can be made these days! (Fig. L)
Now that you see there is hardly anything to it, let's install the change.
First, before wc do anything, look at the hack of the HT-37. If your unit is similar to the author's (serial #259222), you will notice two % inch diameter unused holes, one near the 11 pin control outlet and one near the 50 ohm rf coaxial plug. The phone jack used in our modification is installed in the lA inch diam- eter hole nearest the 11 pin control outlet. The next thing to do is to remove the top cabinet cover by removing the four screws on the sides.
Telegraph Key
V
Standard Phont Plug
FIGURE 2A
Single Burton Microphone Connector
7
o-
A
Amphenol Double P^n* Microphone Conr.ec tar* -±
Standard Phone PHig
FIGURE 2B
T^
Ta
Push-To-Tai* Mike Eland
46
73 MAGAZINE
TOUCH — IT'S ON!
".
a
%
TOUCH — IT'S OFF!
® MOTHER'S DAY SPECIAL
TUNG-SOL TOUCH CONTROL LAMP KIT
WITH THE AMAZING DYNAQUAD ELECTRONIC SWITCH Responds to a touch of your finger. This fascinating electronic hobby kit makes a bectu- tifuIly^styTed lamp of polished walnut ond brass finish that seems to work as if by magic.
Touch the base, it lights! Touch the center flange, it goes out! Friends are mystified until you let them in on the secret.
Dynaquad switch is completely electronic — completely concealed, There's nothing to break, or wear out. Works from standard 110v AC outlet.
Kit is complete, except for bulb and shade — something the woman in the house usually prefers to select. Dynaquad switch is fully assembled. There are only six wires to be connected. Just pliers and a screwdriver and the easy-to-follow instructions make building this attractive and useful lamp an hour's fun anyone can enjoy.
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Then turn the transmitter upside down (after removing the 5R4GY rectifier tube so it doesn*t get squashed) and proceed to remove the screws that fasten the bottom cabinet half. Now install the phone jack (make sure it is not the shorting type when the plug is out) and route a piece of hookup wire from R51 (220 ohm resistor) to the phone plug. Solder the wire to the resistor on the end opposite to where it is attached to the cathode pin 3 of VI5B (X 12AT7). Solder the other end of the wire to the hot connection of the phone plug. Replace the cabinet halves, the rectifier tube and that's it- Fig 2 shows two possible methods of use. (A) shows the simple expedient of using your telegraph key as a control device. With this method, the VOX sensitivity control is turned fully clockwise to prevent any audio from pick- ing the relay through the VOX circuitry. All operation positions work normally except that
M«
FONE
P.O. BOX 312
603*225-3358 CONCORD, N. H.
in the VOX position the transmitter is put on the air with the closing of the telegraph key.
Fig 2 (B) shows how a cable with suitable microphone connectors is uesd with a push to talk mike stand. In this case, since the hot lead of the microphone cartridge is grounded when the push to talk switch is open (true on an Actatic model G stand), the VOX sensitivity does not have to be turned down. To use this method, just insert the phone plug in the rear, and the mike connector in its normal position on the front panel, and you are in business. If you should desire normal VOX operation again (after the kids have left the shack) just pull out the phone plug, lock the push to talk handle in the closed position and everything works as if nothing had been done.
That's it ... a simple enough change to add another degree of versatility to an already fine piece of gear.
W2ZBS
"BEAMED-POWER" ANTENNAS and ANTENNA SYSTEMS
The Choice of the Discriminating Communication Engineer ... the Man who Never Settles for Any- thing Less than THE- VERY-BEST!
with 3
MATERIAL DIFFERENCE !"
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Send for PL64 condensed data and pricing* cata- log, describing the World's most Popular an- tennas from $6.95 to $999,00, Expanded data sheets — your favorite band, also available.
Communication and TV Antennas
rex
LABORATORIES
ASBURY PARK 25, NEW JERSEY, U,S.A*
MAY 1964
47
#
I
i
Sk
#
1
Featuring the same unmatched performance, reliability and crafts- manship you have learned to expect from Swan Electronics. These units are now in production.
■;
mammmmmmm
m
t*mm$ciz§.
y&nims ■ ■ ■
w-W-!- WW
SWAN-406 MIMATDIUXKII
CONTROL UNIT
Mi tiiature design for mobile mount in g in conjunc- tion with the Swan-400. May also be used for fixed station operation if desired.
• Phone Band Coverage as follows; 3-84.0, 7.1-7.3, 14,15-14.35, 2L25-2L45, 28-5-28. 7T and 28J-28.9 MC. (These ranges can be easily adjusted to cover other segments, if desired.)
• Direct reading dial scale calibrated in 2 kc incre- ments. Dual tuning knobs provide choice of fast 6:1 ratio or slow 36:1 vernier tuning.
• Transistorized VFO circuit with Zener regulated power supply,
• Temperature Stability: Warm-up drift Is virtually eliminated due to separation of the VFO from the transceiver's relatively high temperature, and by the use of transistors. Oscillator circuit is fully compensated for wide excursions in ambient operat- ing temperature,
• Voltage Stability: Zener voltage regulator completely isolates oscillator circuit from power supply varia- tions. Input voltage can change plus or minus 50 per cent with no change in oscillator frequency.
• Mechanical Stability; Extremely rugged construction and precision tuning system establishes new stand- ards In operating smoothness.
• Includes receiver R.F. Gain control; thus the 406 functions as a mobile control head, and makes it possible to install the Swan-400 transceiver in the trunk, if necessary.
• Compact size allows installation on the automobile dashboard within easy reach and visibility of the operator. Supplied with
mounting brackets and hardware, Only 3 in, high, 4^4 in. wide, 5 in. deep, 3 lbs. weight
.SWAN-400 5 BAND IOO WATT
Operates with the Swan-406 or
420 Frequency Control Unit, and
the Swan-1176, 117AC, or 512 DC Power Supply,
Covers the 10, 15, 20, 40 and 80 meter amateur bands.
Transmitter Power: 400 watts SSB, P.E.P. input, dist prod, down 30db. 320 watts CW input, 125 watts AM input. PA efficiency: 60 per cent
Two 6HF5 PA tubes, 6GK6 Driver Stage, 7360 bal. mod. 17 tubes, total.
Output Circuit: Wide range Pi Cou- pler, Coarse and Fine Adjustment
Panel Controls: Function Switch, Sideband Selector, Phone-CW Transmit Selector, Rec. A.F, Gain, Headphone Jack, Mic. Jack,
Mic. Gain, Carrier Bal.f P.A. Tune, PA Grid, PA Fine-Coarse, Band Selector.
Load
Grid Block CW Keying, Key jack on chassis rear.
Trans, Metering: 0-800 ma. P.A. Cath., and Grid Current position for over-modulation indicator.
Provision for Plug-In VOX Acces- sory,
High Frequency Crystal Lattice Fil- ter, Common to transmit and re- ceive circuits. 3 kc bandwidth. Unwanted sideband more than 40 db down. Carrier down over 50 db.
Overall audio bandpass^ essenti- ally flat from 300 to 3300 cycles, transmitting and receiving.
JUST THREE YEARS' AGO Swan Engineering introduced the now famous SW-120/140/ 175 single band SSB transceiver. Our company began as a one-man operation with Herb Johnson, then W7GRA, now W6GKL Jn three short years we have grown to include a talented management team of 13 licensed hams, and a top-quality production department. Our success would have been impossible without the tremendously enthusiastic support of Swan owners. We will continue our policy of providing the finest quality control and reliability, top dollar value, and customer service second to none. And now the latest development from the Swan laboratories. We think you' It agree tbat the Swan-400 is the most versatile, feature-packed transceiver on the market, regardless of price.
WB6AWJ WA6EDJ K6HON WAE1VC WB6JBL W6KNV
W60FT WA6QGLY K60UK W66KI WASYKZ WA6ZAC K6ZIK
•
*
L
I
A
Separate frequency control heads for maximum stability and ver- satility, in fixed, portable or mobile operation. Read the following specifications, and we think you'll agree. — The new Swan-400 is for you. _ —
©
wvwflft
►*.*«■
SINGLE SIDE1IAND TRANSCEIVER
Single Conversion Design. Spuri- ous emission and image response down more than 80 db.
Receiver Sensitivity: better than .5 uv for 10 db signal-plus-noise to noise ratio.
Wide range AGC system, S-rneter functions automatically when re- ceiving.
ACCESSORIES
AC Power Supply, Model 117B. .,.
500 Watt Mobile Power Supply, Model 512, Plug-In VOX Unit, Model VX-1 .......
100 KC Crystal Calibrator.
Built-in Speaker. Also provision for external speaker
5Vz in. high, 13 in, wide, 11 in. deep. 15 lbs. weight
C145
$25
SEE YOUR SWAN DEALER TODAY!
LECTRONICS CORP.
Oceanside, California
SWAN-42© FUIX
COVERAGE FREQUENCY
CONTROL UNIT
Designed for fixed station operation in conjunction with the Swan^fOQ SSB Transceiver. May be in- stalled for mobile operation if full frequency cover- age is desired.
• Full frequency coverage of 10, 15, 20, 40, and 80 meter amateur bands in 20 ranges of 200 kc each, including WWV range as follows: 3,4-3,6, 3,6-3.8, 3.8-4.0, 7,0-7.2, 7.2-7,4, 14.0-14.2, 14.2*14.4, 14.8- 15.0, 21.0-21.2, 21. 2-21 .4, 21.4-21.6, 28.0-28.2, 28.2-28,4, 28,4-28.6, 28.6-28,8, 28,8-29,0, 29.0- 29,2, 29.2-29.4, 29.4*29.6, 29.6-29.8,
• Direct reading dial scale calibrated in 2 Kc incre- ments. Dual tuning knobs provide choice of fast 6:1 ratio or slow 36a vernier tuning.
• Transistorized VFO circuit with Zener regulated power supply,
• Temperature Stability: Warm-up drift Is virtually eliminated due to separation of the VFO from the transceiver's relatively high temperature, and by the use of transistors. Oscillator circuit is fully compensated for wide excursions in ambient operat- ing temperature.
• Voltage Stability: Zener voltage regulator completely isolates oscillator circuit from power supply varia- tions. Input voltage can change plus or minus 50 per cent with no change in oscillator frequency.
• Mechanical Stability: Extremely rugged construction and precision tuning system establishes new stand- ards in operating smoothness.
• Matches the Swan-400 in height, depth, and styling. Plugs directly into the ^00, 5^ in. high, 6^4 in. wide, 11 in. deep, 9 lbs. weight.
• Supplied with mounting base which joins the 400 and 420 in a neat
tilt-up arrange- ment for desk top operating. (As il- lustrated above.)
Gardner Modulator Revisited
Barry Hoyt WA2AKK 25 Edge wood Rd Peekskill, N. Y.
Soon after I passed my General Class exam, I searched for a simple and effective means of modulating my 50 watt ( W rig. As I had not yet accumulated enough junk to make a plate modulator economical, some other form of modulation would have to do. I ran across the Gardner circuit in Volume five of "Hints and Kinks" and built the whole thing for less than five dollars, exclusive of tubes. It was my orginal intent to use this as an interim modu- lator until I could get something better going. The little thing worked like a dream and a slight modification of the original design made it even more effective. However, the time came when the lure grew too strong, and I built a plate modulator, The thing was large, heavy and noisy (the surplus modulation transformer tvas running a shade over its ratings) and, to my great surprise, showed no noticable im- provement in modulation strength and quality when compared to the Gardner circuit in the same QSO, These tests were made over both long hauls with marginal signals and local work. When the shack was moved to the base-
Audio
Input
Modulated R F Amplifier
o
B + For Speech Amplifier
FIGURE !
ment, I went back to the little cathode modu- lator and have been using it exclusively for over three years with consistent reports of ex- cellent audio quality and good "punch/* Its operating qualities and simplicity makes one wonder why it has been almost complete]) ignored for so many years.
Circuit
The basic circuit is shown in Fig 1. It con- sists simply of a class A amplifier connected between the cathode of the modulated stage and ground. Modulation is applied simultane- ously to the grid plate and the screen if the modulated amplifier happens to be a tetrode or pentode. This eliminates the need for a coupling transformer with its associated im- pedance matching problems and also makes it possible to eliminate the need for a separate plate power supply. In addition, high voltage for the speech amplifier is available through an audio choke and capacitor filter from the modulator plate. Thus, if supplied with fila- ment voltage, the modulator can be "installed" simply by plugging it into the cathode key jack of the final amplifier. This makes it an at- tractive circuit for use with portable rigs and most inexpensive CW-only rigs.
Fig, 2 shows the complete circuit with a speech amplifier using a more modern tube than the original. In addition, a 500 ohm po~ tentiometer has been added in the cathode of the 6Y6 for adjustment of operating conditions. The speech amplifier shown is for use with a high impedance mike, A carbon mike circuit is shown in Fig, 3 which has been used success-
50
73 MAGAZINE
NEW ! !
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for full details
on these great
new Swan rigs.
Then order from
HENRY!
SWAN 400 $375
SWAN 420 $120
11240 West Olympic Blvd. Los Angeles 64
Ph. (213) BR 2-0861, GR 7-6701
Butler lf Missouri ORchard 9 3127
93 \ N. Euclid AvCi| Anaheim, CaJif#
PR 2-9200
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fully wth an ARC-5 transmitter in stand-by and mobile service. With 1000 volts on its plate, the ARC-5 can be run at up to 100 watts input on phone. With currently available clynamotors delivering 1000 volts output, this combination makes a good, choice for a powerful but in- expensive mobile rig if you have a husky elec- trical system.
Construction
It is only necessary when building this unit
to keep all leads short which are goiug to the
first speech amplifier stage and to shield the
lead from the mike connector to the grid of
I/2-I2AX7
I/2-I2AX7
the 12AX7, If rf feedback occurs, it may be necessary to filter the input circuit with a -001 pf capacitor to ground and an if choke in the grid lead.
If the modulator is to be permanently stalled in the transmitter, it might be better to take supply voltages for the 6Y6 screen and the speech amplifier plates from an existing high voltage source in the transmitter through a dropping resistor. A switch, S-l is provided to change the transmitter over from phone to CW. The circuit as shown is capable of modu* latin g an amplifier whose plate current in this
6Y6
Q
Microphone
Cathode Of ModuloTed Amplifier
6 3 VAC
FILAMENTS
FIGURE 2
LI — any small audio choke, 2h or more or the plate side of o small output Trans- former
Rl — nominally 2000 ohms, 2W, adjust to higher valve if 6Y6 screen voltage ex- ceeds 1 35V
MAY 1964
51
6AU6
6Y6
Cor & on Mftraphane
FIGURE 3
mode o£ operation does not exceed about 100 to 120 ma. To find this current for your trans- mitter, look up the recommended plate modu- lated conditions for your final tube at the volt- age available and use about 80^ of this value, If this is over 120 ma as mentioned above, use two 6Y6 tubes with all elements tied in parallel.
Make sure, at any rate, that the maximum screen voltage of the 6Y6 (135 volts) is not exceeded and that the plate voltage of the 12AX7 does not exceed 300 volts. Be sure to check these voltages on standby as well as when the transmitter is under full load as on occasion these might be exceeded by quite a bit and you will be wondering where all the 6Y6s are going.
One more word of caution; be sure, especially when working with fairly high volt- ages on the final, to apply filament voltage to the 6Y6 before any high voltage is applied to the final This will be taken care of in most rigs if the filaments of the modulator are tied in with the other filaments or are at least ar- ranged so that they come on when the others are turned on. In arranging phone— GW switching, do not remove filament voltages from the modulator when operating CW lest you inadvertently switch back to phone and immediately apply high voltage,
Adjustment and Operation
Adjustment, once you get the hang of it, is almost as easy as plate modulation. After checking for errors and the usual smoke test, tune the driving stays in your transmitter for normal grid current in the CW position. When you switch in the modulator you will notice that the pot in the cathode of the 6Y6 controls the final plate current to a great extent. This is where this particular circuit differs from the original. Adjust the plate current using this control to a point somewhat below the rated operating current and tune the final for maxi- mum output as indicated on an rf voltmeter, ammeter, FSM or scope. Bring the plate cur- rent up to the value determined earlier in the article and advance the gain control while
speaking into the mike until there is a flicker in the plate current on voice peaks. If you have a scope available it would be wise to adjust the modulator until some clipping action is seen. If the plate meter is observed to flicker down- ward or clipping appears on the scope before any appreciable upward modulation takes place, increase the loading to the final or de- crease the plate current with the cathode pot, or both, until more upward modulation is indi- cated on the scope or the plate current is ob- served to flicker slightly upward*
It will be difficult to note a dip in plate cur- rent as the final tank is tuned through reson- ance with the modulator in the circuit and you must use some means of indicating rf intensity to tune up. This can be anything from a 9c neon bulb to a Bird wattmeter as long as you can tune for maximum output. Don't worry about blowing your final during this process as the modulator will prevent excessive plate cur- rent.
At this point you should conduct a test with a station who is receiving you about S-9 on a QRM-free band to determine that your signal is free of hum? noise, distortion and splatter. Once this test is passed, you are ready to enjoy many trouble free QSO's— and if you don't tell any one that you're not plate modulated, they will never know.
SUBSCRIBE TO QST
By sending in your subscription to QST through the Radio Bookshop subscription service you get all of the regular benefits as an ARRL member plus you help us out. You lose absolutely nothing and you give us just that much more of a lift, How about it? Subscription is $5,00 per year in the U. S,r including your ARRL membership. $5.25 in Canada; $6 else- where.
SUBSCRIBE TO CQ
If you are going to subscribe to CQ, at least do it through us. This will help us and drive CQ out of what is left of their minds- Subscription is $5 per year in the LL S., Canada and Mexico and $6 elsewhere.
The Radio Bookshop gives you this guarantee: if you subscribe to any magazine through Radio Book- shop and that magazine goes out of business before the end of the subscription, you will receive the unexpired portion of that subscription in 73Js. This is a point that has been worrying many amateurs lately as one magazine after another has been biting the dust.
Send your name, call, address, and zip code. Specify which magazine you want and if this is a new or renewal subscription. Don't forget the money too.
Radio Bookshop, Peterborough, N. HL
52
73 MAGAZINE
BROUGHT BACK BY POPULAR DEMAND! BURGHARDTTS TRANSCEIVER HIT PARADE.
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$1150.00 115.00 1 20.00 198.00
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14.50
109.50
$369.00 1 1 0.00 119.50
$389.50
79.50
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279.50
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3tC
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Swan 400 |
$375.00 |
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Swan 406 |
VFO |
65.00 |
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VFO |
1 20.00 |
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Yes, here ore lower prices on fop qualify-fully recon- ditioned and fully guaranteed equipment than you have ever seen before anywhere- We invite comparison, we challenge competition,
73
Stan Burghardt W0BJV
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AMATEUR USED EQUIPMENT LIST
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■ ■ - 9 -
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BC 22IP Frequency meter
CENTRAL ELECTRONICS MM-2 Scope CENTRAL ELECTRONICS 600L Linear .. COLLINS 30L-1 KW Linear, new demonstrator
DRAKE 1A Receiver .
ELM AC AF-67 Transmitter
GLOBE CHIEF 90 CW Novice Transmitter
GONSET G-66 Receiver and 12 volt supply
GONSET GSB-100 SSB Exciter , . . . ,
GONSET GSB-101 Kilowatt Linear
HALLICRAFTERS HA-2 two meter transverter with P26 match
AC Power SudpIv ■ *
HALLICRAFTERS HA-8 Splatter Guard . ,,
HALLICRAFTERS HT-32 AM/CW/SSB Transmitter
HALLICRAFTERS HT-32A AM/CW/SSB Transmitter
HALLICRAFTERS HT-37 AM/CW/SSB Transmitter
HALLICRAFTERS $-119 Receiver (new)
HALLICRAFTERS SR-150 Transceiver with P-150 AC Supply,
P-150 DC Supply and Mobile Mount
HALLICRAFTERS SX-10M1IA
HALLICRAFTERS R-46B Speaker
HALLICRAFTERS R-47 Speaker
HALLICRAFTERS HT-41 KW Linear ....
HEATH VF-1 VFO
HEATH HO- 10 Monitor Scope
HEATH SB-IO SSB Exciter , .
HEATH TX-l Apache Transmitter
JONES MICROMATCH 261/262 SWR Bridge and Meter
JOHNSON VALIANT AM & CW Transmitter
JOHNSON VALIANT II factory wired (like new)
JOHNSON RANGER I Transmitter .-
JOHNSON VIKING II Transmitter JOHNSON 122 VFO
JOHNSON 250-39 TR Switch
JOHNSON 250-46 Phone Patch
KNIGHT R100 Receiver with Speaker (like new)
LAFAYETTE HE-30 Receiver with Speaker (like new)
NATIONAL SW-54 Receiver
NATIONAL NC-88 Receiver .
NATIONAL NC-3Q0 Receiver with speaker
P&H LA400C Linear Amplifier (like new)
SWAN SW-120 Transmitter
SBE33 Transceiver — excellent
SWAN SW-12 DC 800 volt mobile supply
V-M 725 3 speed monoral recorder (demonstrator)
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$ 49.00
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ing
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» . * *
■ -9 1 P
i ■ I
■ * *
249,00 15.00 299.00 319.00 279,00 29,00
549*00 189.00
7.00
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229.00
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53
Now Hear
Ti nis
Fellow Amateur
Frank Phillips W4LCY Bang kok, Tha i tand
Recently; there have been several notable amateur personalities who have expressed their views concerning the fate of amateur radio. Generally speaking, all of the views have made one thing clear, and that is, the amateur will have to increase his value toward public service in order to maintain his existence. Many qualities and quantities were noted and pointed out which over the years we amateurs have taken for granted and as a result, has caused us to lapse into a false sense of security*
In looking over the ham bands in their pres- ent state, it is quite obvious from the way the frequencies are being utilized that a general up-dating is in order, Progress can be made in technical achievement, operating proficiency and proper use of equpiment. I agree with one author in that the frequencies are being used to a great extent in "projecting personalities" rather than in something more constructive. It is all too true that many amateurs are more adept at buying their equipment instead of building it, with the consequent loss of techni- cal ability. No doubt this is the aftermath of "our times" and the fact that "getting on the air" has been made too easy* However, the purpose of this article is not to review what has been said previously, but to point out that the amateur is not the only one lacking in incentive and regardless of how perfect, or valuable we may become, it will have little bearing on the outcome of future international conferences. If this bit of information shocks you, then the forthcoming information is in- tended to enlighten you.
Previous discussions on this matter have been glaringly superficial as they have tended to place the amateur in a poor light while supporting the other inhabitants of the fre- quency spectrum as being faultless, infallible and above reproach. Nothing could be further
From the truth. We are all familiar with the fact that there are two sides to everything. Let's take a look at the other side- The side that various spokesmen are reluctant to bring out; depicting the typical human trait of deliberately avoiding the responsible issues, or not being adequately informed on the sub- ject to a point where they can speak factually. For some time now, the amateur service has been a sore point with a number of countries who would much prefer to see the ham bands used for other purposes. This is not to say that they would use the frequencies for the general welfare of the international public, but it is to say that they would like to see them used for their purposes. It is a well known fact that there are countries who are completely hostile to an amateur service* It would not be difficult to comprehend this source of hostility if you were to closely scrutinize the basis for this state of mind. You will find communications systems that are inefficient due to poor en- gineering, there is a shortage of trained per- sonnel to operate these systems, there is op- position to acceptance of new and better modes of communication, there is no insight to any problem related to communi cations, they do not abide by the edicts of the ITU, (except on paper), and communication posts in their governments are filled by political appointment rather than on the basis of technical compe- tence. They have never contributed to the art, and furthermore, they never will They are quick to tell you that there is no need for them to delve into research, or experimentation, when they can purchase what they need on the open market. From the foregoing, one can deduce that this is not a healthy environment for the support of an amateur service- They just don't want any. They point out that the added load of an agency to handle amateur
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73 MAGAZINE
affairs and monitoring of the ham bands con- stitutes too much of a bother to warrant an amateur service. What they don't tell you h that they would much rather allot the fre- quencies to business enterprises because of the added revenue in taxes that would be avail- able. How can you possibly sell them the idea of having amateur radio when their outlook is mercenary. It is impossible. So what happens at an ITU conference? They vote against an amateur service! The only way that they would possibly vote in favor of amateur radio is that if there were something in it for them. Something tangible, that is.
It is a little known fact that in trying to cope with the frequency problem, one of the retarding aspects to a satisfactory solution is that many representatives do not "see" the problem as those who are more versed in com- munication engineering from a standpoint of long association or experience. In other words, the human factor is more of a governing agent than an enginering one. Just because a person is from the other side of the world, he doesn't comprehend the problem the same way that you do, How the laws of physics, or the re- quirements of an engineering necessity can be altered by human whims has always been the primaiy negotiating obstacle at an Internationa] conference* Nevertheless, it's there,
Also another ironic reality is the fact that many countries whom we have to cajole at the conferences, are, or have been in the past, recipients of technical aid in one form or another. Although original impetus was lacking in the initial stages of radio communication, they are now ^experts" in the field and they are now in the position to vote prohibitively concerning amateur radio affairs. I would also venture to say that if some of the representa- tives at the ITU conferences are indicative of many of the communication officials in govern- ments whom I have encountered, they haven't the faintest notion of the history , achievements, or functioning of an amateur service, This means one thing which is a natural defense when ignorance prevails. If you don't under- stand it? or don't know what it is; vote against it!
In looking over some of the reasons why the non-amateurs have their cold, envious eve on the ham bands, you will find that most of them are about as ridiculous as they can be. As a beginning, there is this notion of public service, A close look at the frequencies being used for shortwave broadcasting will reveal that in the true sense of the word, they are not being used wholly for a public service. Would an intelligent person admit, for exam-
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pie, that Radio Moscow with their type of broadcasting constitute a public service? Let's not be naive. Take any one country as a hypothetical case, Can it be said that the broadcasting of their "virtues" to the rest of the world be in complete accord with a public service. Public service to whom?
It has been pointed out that nearly thirty new countries have come into being as brand- new nations in the past few years, with a strong feeling of pride in their newly found sovereignty and a desire to broadcast their virtues and philosophies to the rest of the world. Is a desire for broadcasting of mere virtuous and philosophical beliefs a truly valid justification for adding more congestion to the present enunciations on the frequency spec- trum? Very few possess technical background sufficient to intelligently sanction modes of communication to fill their needs. Regardless of their capabilities and shortcomings^ how- ever, they axe allowed to vote at a conference,
This brings up another point. It was further proclaimed that in order to foster democracy, tliis is the way it has to be done. With no reference to technical background, every na- tion has a vote. This one aspect alone is the reason the frequency spectrum is in a sordid mess, The allocation of frequencies is no longer a result of necessity, or engineering endeavor, but rather one of politics. Vulnerability to political stratagems is the prime reason for the state of the frequency spectrum today. This must be true, obviously, as the present state of frequency misuse will substantiate this. The complexity of frequency shortage and, frequency misuse presently on a world wide scale is due more to a human factor than a technical one.
Another so-called factor that was brought to our attention was the need for a country's "vital" communications. Monitoring the high frequency bands will further reveal from that which is propagated it is extremely difficult, if not impossible, to differentiate between the "vital" and the inconsequential. Shortwave broadcasting for informative purposes is no longer a necessity as it once was. Even in remote countries people are watching TV programs and not listening to shortwave broadcasting. An objective look at this service will determine conclusively that the multitude of stations are not an absolute necessity. If radio communications is not a toy, or a hobby, then why is it being used indiscriminately in the broadcasting field?
Some learned minds have said that the so- called leading nations have to go along with what is available in the way of administration,
otherwise chaos will reign. What is the higher two-thirds of the forty meter band in the Western Hemisphere if not chaos? In some areas of the world the eighty meter band as well as the forty meter band is chaotic! Ask those who have lived in Asia about the state of the frequency spectrum there. From the low end of the broadcast band to 30 megacycles it is a shambles* For the "authorities" who have never gotten any farther from the continental limits of the United States than to Geneva, the use of the frequency spectrum as it shouldn't be used has already been ushered into that part of the world. Whether a BC receiver is available or not, it makes no difference. A shortwave receiver will fill the bill nicely as the second harmonic of any BC station can be received with no drop in quality. Harmonic filters are just two words in a textbook. If you don't know better, you would believe that the raucous CW signal was a status symbol in Asia. The accepting thing is the signal with 130^? modulation. It is virtually impossible to use the time standard stations WWVH and JJY on 10 megacycles because of the commercial RTTY stations riding on top of them* If you desire to use any particular frequency the usual method to to tune up, the more power the better of course, and then sit on the key for a few days. After you have driven every- body off, you have a clear channel. Every local shortwave broadcasting station has a VFO. As the QRM builds up they shift their fre- quency in an effort to find a clear spot. That is, if they can find one. Frequency allocations? That's kid stuff.
There is one country in Southeastern Asia with which I am thoroughly familiar. The size of this country is about that of Texas. Do you know how many BC and SW stations it supports? Believe it or not, 70. That is a seven and a zero. Seventy. That's not taking into account the military, government and private businesses who have their own net- works. The number is staggering. Now mind you? that is only one country. Multiply that to account for all the stations in Asia and Africa, The ITU? Oh yes, that's in Geneva, isn't it?
In summation , the over-all picture of the fre- quency spectrum indicates that control through present administration is no longer effective. The situation will become progressively worse as time goes on. More and more new stations are clamoring for space which is already non- existent* The countries who are not members of the ITU will use frequencies they deem necessary. The others who are members will agree to the recommendations as long as they are present at the conferences3 or if it serves
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