Issue 61, June 1988
Scanned, OCR'ed, and proofed by Bob "Bacon" Bruhns WA3WDR
Part 97 Rewrite and the AM Power Limit
While the proposed rewrite of the amateur regulations, under PR Docket 88-139, does not appear to add any further restrictions to AM operation, the scheduled 1990 power reduction is retained. Interestingly, the term "peak envelope power" disappears under this proposal. The term transmitter power is defined as "the average power during one RF cycle at the crest of the modulation envelope under normal operating conditions that is present at the antenna terminals" of the transmitter. Although this definition seems vague, and its meaning could be the subject of countless hours of debate, the FCC intends it to mean the same thing as "peak envelope power." Average power is what you see graphically displayed on an oscilloscope. The defined power limit would limit the peak power as indicated by the scope to 1500 watts. With no modulation present, the carrier power, in the case of a plate modulated class-C amplifier, is about 750 watts. With full modulation, the scope may indicate more than 5 times that depending on the modulation waveform (even though many of the inexpensive "amateur radio quality" peak reading wattmeters may indicate less than 1500 watts, demonstrating the general uselessness of these instruments).
In Docket 88-139, proposed 97.403, 53 words are used to "grandfather" the 1 KW power input limit, and make it expire in 1990. However, this would be reduced to 35 words, by defining the AM power limit in terms of carrier output power (the same standard used for measuring the output power of AM broadcast stations). The paragraph could be reworded as follows:
97.403 (b) No station may transmit with a transmitter power exceeding 1.5 KW. This power limit notwithstanding, a station may transmit full-carrier A3E emission with transmitting power exceeding 1.5 KW provided the mean carrier power at the antenna terminals of the transmitter does not exceed 0.75 KW.
What Would This Accomplish?
This would rescind the unfair, arbitrary, discriminatory power reduction scheduled to be imposed on AM, while CW, FM and some other modes enjoyed a doubling of their power limits (the SSB power limit stayed about the same). By defining AM as "full-carrier A3" this would eliminate the possibility that amateurs could circumvent the intent of the rules by using "ultra-modulation" or the "upside down tube" circuit, a fear expressed by the FCC as one reason they refused to permanently grandfather the old AM power limit. With ultramodulation and similar schemes, the average (mean) carrier power increases when modulation is applied, exactly as in the case of controlled carrier. The broadcast industry calls this "positive carrier shift", and it can be measured with a simple rectifier type RF voltmeter. With the upside-down tube circuit, the emission is no longer full carrier A3E but reduced carrier. The circuit consists essentially of a high-level balanced modulator which generates a double sideband signal. The carrier is generated independently of the sidebands and can be adjusted from zero to far beyond the normal carrier level for a given set of sidebands.
The above change would bring fairness back to the FCC rules, simplify the wording of the power limit in Part 97, and close the loopholes that have always existed under the grandfathered "DC input" power limit.
Remember, the deadline for comments on this proposal is August 31, 1988. All readers are urged to participate in this rulemaking proceeding. While we are at it, let's take advantage of one more opportunity to bring up the AM power issue to the FCC.
For complete details on the proposed Part 97 Rewrite, see last month's AM Press/Exchange.
W A R N I N G
When cleaning and restoring old equipment, NEVER use a cleaning agent such as "409" or "Fantastik" to clean moulded Bakelite parts. Several would-be restorers have reported the same disasterous result: these cleaners will remove the dirt and grime from the part, but they also permanently remove the shine from the Bakelite! Don, K4KYV ruined some rare National Type A Velvet Vernier dials using that stuff. Another AM'er recently washed the shine off the knobs and escutcheon of his newly-acquired Collins KW-1. Still another antique collector removed the gloss from a beautiful brown Bakelite panel of a 1920's broadcast receiver. Upon hearing the above tales, a veteran antique radio collector/restorer remarked, "I have done the same thing myself." No amount of rubbing and buffing seems to bring back the original gloss, although some success has been reported with automotive paste wax and other substances.
Perhaps some of our readers could help shed some light on this. Has anyone reading this ever had any work experience with the manufacture of Bakelite, or phenolic materials? We need to know exactly what the above cleaning agents wash off. What forms the original glossy surface on moulded Bakelite anyway? Is some kind of lacquer finish applied, or does the Bakelite come out of the mould with a high gloss? Evidently the offending cleaners either wash off a lacquer finish or attack the surface of the phenolic itself and leave behind a roughened etched surface. We have tested these agents on Bakelite parts of no value, and noticed a brown residue comes off the plastic when it is cleaned. At first we thought it was tobacco residue from equipment used by a heavy smoker. When some black Bakelite parts are cleaned with the above agents, not only does the shine disappear; the black color is also removed, leaving behind a brownish-black surface with little gloss.
We are interested in finding a way to restore the original shine. If the gloss is lacquered on, it should be possible re-lacquer the part with same kind of lacquer and restore the finish. If the Bakelite comes out of the mould already shiny, then it should be possible to buff the shine back. If you have any information on this, or suggestions based on your own experience, please write to The AM Press/Exchange, Route 1 Box 281, Woodlawn, TN 37191. We wish to share this information with other readers. This seems to be a widespread problem among collectors and others who attempt to restore old electronic equipment. Very few people seem to be aware that the above cleaning agents can cause this type of damage. The word must be spread, to avoid needless damage to irreplaceable collector's items and fine pieces of classic equipment. Although prevention is to be preferred over the repair of damage already done, we are also seeking any possible techniques to permanently restore any parts already damaged by these chemicals with an authentic finish similar or identical to the original.
When cleaning moulded Bakelite, it is better to stick with warm water with a mild soap solution and a soft rag. Another hint: do not rub too hard with the cloth. If too much pressure is applied, even a soft rag will leave microscopic but visible scratches on the glossy surface.
Canadian Authorities "Not Flexible" on Equipment Issue
A difference of opinion has developed between Communications Canada (the official new name for the DOC, Department of Communications) and Canada's two national amateur organizations, the Canadian Radio Relay League (CRRL) and the Canadian Amateur Radio Federation (CARF). In February, CC proposed a four class Restructuring of the Amateur Radio Service. The three lowest levels of amateurs (A, B, and C) would be required to use commercially designed and marketed transmitting equipment but they could build and use any other gear they wanted. There would be no such restriction on top level, Class D amateurs. The ham groups feel that the "commercial gear" only concept runs counter to the basic premise that the Amateur Radio Service is also an experimental service. They feel that all amateurs should be able to build and experiment with all gear of their own making provided it does not cause interference. "Whether an amateur wants to be a communicator or an experimenter should be left to the individual to decide without being forced by Communications Canada and the Radio Regulations," they jointly say. It appears that CC is not flexible on this aspect. Now comes word that the joint CRRL/CARF working group has developed a compromise solution. They want CC to allow the lowest three level amateur classes to use: (1.) home designed and built transmitters up to 250 watts subject to their being checked out by a level D amateur; (2.) transmitters up to 250 watts built from commercial kits; (3.) home designed and built transmitters up to 10 watts without being checked out and; (4.) commercially made transmitters up to 250 watts. -W5YI Report
Common Sense and Good Engineering Practice
One way to publish information which serves a useful purpose is via a regular newsletter. This costs money and distribution is very limited. Hams have transmitters. It makes common sense for hams to publish information which serves a useful purpose via amateur programming. The cost per person so informed is much less and the distribution is unlimited. Also, the activity uses and develops radio skills as well as educational skills, which is the purpose of amateur radio.
With a 45 minute program which has a regular and large listenership, it makes common sense to start and stay on one frequency and time. This will minimize interference to those who don't choose to listen while maximizing the convenience to those who do want to tune in, set their times to record, etc.
This is an amateur Information service and must be non-commercial and shoe-string cost effective. To reach many people on different time schedules and with changing propagation IARN broadcasts five times every day on 3.975, 14.275 and 28.475. For full fidelity and further listenership are special AM broadcasts on 3.890 and 7.290 Sunday evening during prime time. That is 113 separate broadcasts per week, all of which are under semiautomatic control. The entire concept is the most common sense way to do it. The broadcast schedule is published every month in QST and announced on every program. This makes common sense. Any interference to others is very incidental and certainly minimized. A QRZ before each broadcast would end up causing more problems than it would solve and for many common sense reasons is simply not practical. If you have any common sense suggestions we sure want to hear them.
Glenn Baxter, K1MAN, IARN Net Manager
A comment about the article "Let's Improve AM Operation", May, 1988. While the author does seem to repeat the amateur code, and the general good amateur operating practice ideas we all know, there was an underlying theme."Transmissions should be properly timed ... don't be long winded ... taxing"
"don't mix modes ... same old stuff ... better language, and interesting and quality subject matter"
The lady who didn't like what she heard can tune away. Swl's who don't find a ham in Maine discussing modifying a Ranger interesting, they can tune away. If another ham doesn't like hearing a fellow in Connecticut talk for twenty minutes, tune away. If a ham doesn't like a person near the New Hampshire border having a better "strapping" signal, tune away, or go to work and improve his signal! If Swl's and hams don't like hearing a fellow in Pennsylvania, exchanging lofty jokes and laughter with another fun intending ham near Boston at 1am in the morning, tune away!
THIS IS AMERICA! We don't have any one person in power to stifle individual expression and freedom of speech. Most of the people I've spoken to LIKE the individualism that gets expressed by the AMers. I find them all unique and enjoy the variety. There are countries where 'handcuffing people over ant hills' for not following one persons "vision" is the norm, however I was fortunate enough to be born here in the US!
Dean WA1KNX "The Kleenex"
R. Bruhns, 26 Cedar Valley Ln, Huntington NY 11743
Many AM operators use peak-limiting compressors to increase average modulation without introducing objectionable distortion. However, most peak-limiters have two weaknesses:
- They excessively reduce the level of sounds having high peak-to-average ratios, producing a "squashed" sound.
- They don't provide good control of negative modulation when voice-polarity supermodulation techniques are used.
The sound quality of peak-limiting compression can be greatly improved if the voice waveform is taken into consideration. The voice waveform often has positive and negative peak dissymmetry as great as 2:1. Monitoring voice waveforms with a scope, I noticed that the voice sounds being squashed by the peak limiter were the waveforms with large polar asymmetry, especially the "short a" and "long i" sounds.
If the compressor is less sensitive to the polarity having the higher peak amplitude, the "squashing" can be reduced. As it turns out, this technique not only improves sound quality, but it is easily done, and it also improves the absolute control of negative modulation in voice-polarity supermodulation systems.
A peak-limiting compressor consists of a gain control stage, an amplifier, and a level detector. Some method of full-wave rectification is used to generate a DC representation of the peak level; this is filtered and fed back to the gain control stage. If the output peak level exceeds some arbitrary peak level, gain is reduced until the output level is slightly above that threshold - just enough to produce enough gain reduction to keep it there. (This slight output level overrun is called "compression ratio"; it is measured in terms of "dB-in to dB-out".)
By simply reducing the raw signal level fed to one half of the full-wave rectifier, the desired polar asymmetry can easily be achieved. I have had such great success with 2:l asymmetry that I haven't tried anything else, but you can easily try any ratio you would like. Note, however, that you must desensitize the proper wave-half, or you will more than defeat the purpose. A polarity selector switch can be added; if it has a center-off position, it can even allow normal symmetrical peak limiting if desired. (You may want this feature to demonstrate the advantage of asymmetrical peak limiting over the usual symmetrical kind.) Note also that the peak limiter output will increase when correct polarization is selected.
(P5-1) FIGURE 1 - AN ASYMMETRICAL PEAK-LIMITING COMPRESSOR
Refer to Fig 1. Pre-compression gain is set by R1. Input audio is amplified by U1. T1 is driven so that the level at either end of its secondary winding is about the same as the output level from U1. The output from T1 is full wave rectified by diodes CR1 and CR2. With S1 in position 2 (center), the rectifier will be equally sensitive to peaks of either polarity (no asymmetry), while if S1 is switched to position 1 or 3, the sensitivity will be cut in half for waveform peaks of the selected polarity (2:1 asymmetry). The resulting full-wave-rectified waveform at the output of CR1 and CR2 is peak detected by Q2, filtered by R15, R16, C5, R17 and C6, and fed to the variable shunt MOSFET Q1. Output level is set with R8, and output polarity can be reversed with S2.
For simplicity, imagine S1 is in position 2 (center). If the output level of T1 exceeds about 1V peak-to-peak, the peak detector output causes MOSFET Q1 to begin to conduct, reducing the audio fed to U1a. (A FET will shunt low AC voltages with relatively little distortion; the audio voltage to Q1 will be about 10 mV p-p.) Any further increase in input level will only result in a slight increase in output level, producing correspondingly greater gain reduction. Thus the output signal is peak-limited to about 1V peak-to-peak. If S1 is switched to positions 1 or 3, the peak detector will be desensitized to peaks of one polarity, or the other. The effect is best monitored with an oscilloscope, and it can be done over the air if necessary.
Line levels to and from the compressor are expected to be about 0.1V rms. Higher input levels can be used by reducing the setting of R1. Higher output levels can be produced by turning up R8. The modulator is expected to have flat frequency response and good phase response following the compressor.
Insert the compressor between your audio preamp and your modulator. Set S1 (polar asymmetry) to the center-off position, and set R1 (compression) about mid-scale. Set R8 (post-compressor gain) for about 50% modulation. Set S2 (modulator polarity) so that your higher peaks are in the positive direction. Now try both positions of polar asymmetry. One of them should permit large positive modulation, while maintaining control of negative modulation; this is the setting you want. Finally, set your post-compressor gain for maximum positive modulation, or 100% negative modulation, etc, depending on your particular station setup.
Close-miking is advisable, for several reasons: room acoustics are usually bad, directional mikes sound "warm" up close, and RF, hum and noise problems are minimized when you reduce preamplifier gain.
IN CASE OF TROUBLE
Audio equalization should be accomplished in the preamp feeding the compressor. Any significant phase distortion or frequency response variations following the compressor will defeat its purpose.
Excessive bass boost or bass cut will reduce polar asymmetry. Polar asymmetry can usually be optimized with a small amount of bass boost, but this depends on the microphone, the voice, etc. Experimentation will be necessary. If you expect to achieve voice-polarity supermodulation, your transmitter and modulator must be able to handle the large peak powers involved. If they can't, it won't work.
This compressor can add over 30 dB of gain. If you have RF leakage into your audio, if your modulator "talks back" to you, if you have loud background noises, etc, you will have problems. Shielding, filtering, grounding and room acoustics become more important when advanced techniques such as compression are used.
Your MOSFET may require different bias voltage. If necessary, try changing the value of R20. Too high a value here will produce excessive output, while too low a value will result in low gain.
It was 1963 when I first started listening to AM on 3885 as a teenager. Little did I know that 25 years later I'd be recreating that introduction to ham radio and enjoying it even more the second time around.
Back then, I had a bedside Hallicrafters S-40 that was acquired to listen to late night rock and blues from such illustrious stations as WLS, WCFL, WSM and XERF. Feeling inquisitive one night, I wandered onto the ham bands and was hooked by the fascinating QSO's I monitored on 75 meters.
The talk about "home brew" rigs running a "full gallon" quickly caught this Kentuckian's attention. In short order, I got my novice license and started on two meter AM with a Heath "Twoer", graduated to technician and got on six with a Clegg "99er" and with my conditional moved onto HF with an NCX-3: my fatal mistake.
Looking back, the early 60's was a period of turmoil for ham radio and I fell under the influence of "progressive" hams who steered me in the direction of SSB, a mode that had become quite popular with the advent of inexpensive transceivers. I quickly became disenchanted with "quick break" QSO's with other appliance operators and went back to listening to AM. While I could run AM (with carrier insertion) it was a poor substitute for high level modulation and I spent more time listening than talking. At the same time, a series of events occurred that took me away from the ham bands: getting a driver's license, socializing with the opposite sex, going to college, getting a job, getting married and raising a family. Needless to say, I lost touch with ham radio and I let my license lapse without even knowing or caring about it.
Now comes the reawakening! At the ripe old age of 39 and bored with TV I dust off my old 75A-1 (picked up at a flea market while still an active ham) and start hearing familiar voices... What a surprise to hear "K4KYV - Woodlawn, Tennessee" come through the speaker as if out of a time warp. In fact, I spent most of my earlier ham years listening to Don being QRM'd and generally harassed by SSBers who felt the entire spectrum was their domain.
Quickly, I realized that there were a lot of other AMers, many of whom were relatively young but like me appreciated the interesting conversations and pleasant listening conditions that AM offers.
Then I picked up a copy of "QST" and saw an ad for SPAM. How exciting to learn that here was an active organization devoted to AM. From SPAM I received information about the "AM Press/Exchange" and maybe I shouldn't have been surprised to see K4KYV as the editor.
It took me no time to qualify as a SPAM auxiliary member, using the SPAM SWL report forms and other helpful information provided by Floyd, WA5TWF. One of my first confirmations was from Hoisy, W4CJL, the founder of SPAM, who offered further encouragement to get my license again and join the growing group of active AMers.
Hoisy's encouragement was complemented by that of many other AMers who took the time to not only return the reception reports but also include nice notes, letters, QSL's and photos. Feeding on this encouragement and the challenge offered by the "SPAM 100" award, I found my spare time being spent with the phones on instead of in front of the TV.
In reviewing my first 100 confirmations a couple of facts about AMers become evident -- they are responsive and growing in number. My percentage of confirmations was over 85% and more than one third even included QSL'S. Many said it was their first SWL report and I caught many more during their first AM QSO (proof that AM is growing).
I've picked up a battered Valiant and dusted off my old magazines in search of some home brew projects. More importantly, I'm studying and will be going for my license again soon. I want to get back on the air and have a chance to thank all of the AMers who have helped and motivated me to get back to what truly drew me to ham radio in the first place: friendly, interesting and informative roundtable QSO's using a mode that is technically challenging and ultimately pleasurable listening.
EDITOR'S NOTE: Regretfully, we are unable to properly credit the author of this article. There is no name on the manuscript, which got inadvertently separated from the mailing envelope. If the author will notify us, he will be fully credited next issue.
MEET THE AM'ers
(P8-1) Marty Drift WB2FOU/5. His AM station consists of a Heathkit DX-100 transmitter and RX-1 Heathkit receiver. Antennas are 80 and 40 metre bazooka and CL-33 Classic for 20-15-10. Click to view photo.
(P8-2) S.P.A.M sign created by Fred Schrader, W5JKD. This is not a hardback sign but a banner suspended from a self-supporting wooden stand. It was used by the "Houston bunch" in 1987. Photo by W5JKD, Priddy, Texas.
Click to view photo.
IARN "Broadcasters" on the air at K1MAN.
(P9-1) Louie, N1EHI. He is blind. Note the Collins KW-1 for which Radio Moscow stepped aside. Click to view photo.
(P9-2) Bill, N1EHM, at K1MAN "Studio Four". Yea em for ever! No need to pirate from here... it's legal. But legal amateur broadcasting on 3890 not welcome by some members of the AM community, while IARN claims amateur support by 3 to 1 or better in favor. Click to view photo.
How I Discovered S.P.A.M.
by Bob Dennison, W2HBE
I was born in Salina, KS in 1921. The stock market crash of October 1929 marked the beginning of the great depression. Then, in December, my father died. I was in third grade and it was a devastating experience, casting me into a state of deep depression. The following year, my mother bought a Philco model 90 radio and I began to live again. I was fascinated by the glow of the tubes and would lie on the floor looking up into the bottom of the cabinet so I could watch the vibrations of the loudspeaker cone. Oh, how I wanted to know what made it work !
During the next few years I read every book in the public library on Thomas Edison, Marconi, electricity. chemistry and wireless radio. I built a chemistry lab in the basement and started collecting old battery radios, magnets, wire, train transformers, Ford coils, etc.
I met Louie Davis when I was in fifth grade. His older brother was in the Signal Corp and had copies of QST, several Western Electric headphone sets and some galena crystals. With these we tried to make a spark transmitter and a crystal set using clothes lines for aerials but results were nil.
Mr. Flamm who lived between us gave us some old radio tubes, tuning condensers, knobs, rheostats and phone jacks. Louie wound a power transformer using laminations from audio transformers. We pooled our parts and soon had a three tube set working, in a corner of his basement. I still recall the thrill of pulling the headphones on and hearing the announcer saying "This is KMOX - the Voice of St. Louis". I knew then that I must have my own radio.
Louie designed a set for me that used a 24A detector, a 27 audio amplifier and an 80 that half-wave rectified the ac line voltage so that no power transformer was required. Two train transformers supplied the filaments. Rheostats from Mr. Flamm controlled filament current and they ran so hot you choked on the phenol coming out of the bakelite bodies. The primary windings of audio transformers were used for filter chokes. The screen-grid by-pass condenser came from a Ford coil. I paid 12 cents for a 2000 ohm carbon bias resistor for the 27 and Mom gave me $2 to buy a pair of headphones.
Yippee ! It worked ! Everyone in the family listened to it. I took the set to Phillips school and all the kids in sixth grade took turns listening. Each day I rushed home from school to eagerly comb the broadcast band for new stations. One day I discovered the 160 meter ham band and heard W9NOE, Duane Hoisington, who called himself "Little Boy Blue" chatting with Charlie Larsen, W9FEL, who was talking about his new ribbon mike. This was back in the spring of 1934 and, yes, you guessed it, W9NOE was the same 'Hoisy' who many years later founded SPAM. But, wait a minute, I'm getting ahead of the story!
Two years later I became W9YRQ but I never worked Hoisy because he was now in college. Time went by. I graduated from high school, went to college, served in the Navy, married, raised a family and retired. To celebrate my 50th anniversary as a ham, I decided to 'look-up' the fellows who had been hams in Salina before Pearl Harbor. I discovered that Hoisy was alive and well and living in Alabama. He told me about SPAM and in due time I became a member. I still have not worked him on the air. I have a heart pacemaker so am limited to using low-power. I am thinking of building a small 10 meter AM rig - then maybe when the skip is just right I'll finally get to talk to "Little Boy Blue" !
AM Tips and Techniques
Q. "My Collins 75A4 receiver is experiencing stiff tuning and frequency jump. Could this be an electrical and/or mechanical problem?"
A. In the December, 1974 issue of Ham Radio, W3AFM, Paul, wrote an article detailing the procedure to eliminate this problem. Incidentally, I followed the same steps in eliminating a similar problem with my 75A4. Very simply, according to Paul, the bulk of the problem exists inside the PTO. He advises the following steps:
1) Set the tuning dial to 14.000 MHz.
2) Next, remove the vernier knob, mounting plates, ring gear and pinion.
3) Soak the parts in mineral spirits. Remove all the dried grease.
4) Then, from the top of the receiver remove the tuner dust cover, top and side screws of the PTO rear cover plate, and set screw and spring of the passband tuning bronze band. Loosen the two set screws of the tuning shaft, immediately to the rear of the flexible coupling.
5) Remove the bottom plate from the bottom of the receiver. On the middle-bracing chassis cover plate remove the front two screws and loosen the rear two screws. This will permit the plate to he tilted so the PTO can be pulled out of its shaft coupler when the time comes. Make a sketch of the PTO connections and mark the chassis with a felt-tipped pen to facilitate reconnecting the wiring correctly when the unit is reinstalled. Unsolder the three power leads and the coax.
6) Pull out the PTO. Examine and repair the tuning-shaft grounding wiper secured by two tiny Phillips-head screws. If the shaft is rough loosen the screws, bend the wiper slightly forward so it rides on a smooth portion of the shaft and apply a touch of grease to the contact point.
7) Remove the screws holding the PTO cover and carefully slide it off. Drop a few drops of 3-in-1 oil on the front bearing, on the rear felt washer, and on the cam rollers. Put a dab of grease in the rear sleeve bearing (inside the rear of the PTO can). Rotate the tuning shaft back and forth a few times. Work the cam followers in and out about an eighth-inch (3-mm) or so and lubricate them. Grease the cam surfaces. You can now replace the PTO cover.
8) Replace and reconnect the PTO. Oil the turns counter, located between the PTO and the front panel. It should be possible, from the front panel, to turn the dry shaft with bare fingers. Grease the vernier knob assembly, gears and bearings, and remount the knob. Reset the knob to 14.000 mhz, using the crystal calibrator to make sure the receiver is actually tuned to 14.000 MHz, and try it out.
For those who have the 75A4, I would recommend the following changes/modifications:
1) Modify the 1st Mixer and 2nd Mixer stages (a number of excellent articles have appeared in early issues of QST, Ham Radio, etc.,copies can be obtained by writing me - W3WZ). Avoid the 7360 mod! These tubes are too expensive to procure.
2) Remove D.C. voltage from the mechanical filter.
3) Remove B+ from the A.V.C. rectifier.
4) Install a .01 capacitor from pin 6 of product detector.
5) Remove the 100 mmfd. coupling capacitor from the B.F.O. and install a 15 mmfd.
6) To improve the audio, remove R71, 33K from V13 and replace R109, 390K with a 750K. If hum appears after removing R71, leave it in.
7) For greater I.F. gain, remove the 22K from across L27. Please note that many of the 75A4 modifications that appeared in the 1960s attempted to make the receiver more "compatible" with SSB. However, their implementation, in many respects, did not deter the receiver's A.M. performance.
West Coast Report
S.P.A.M. skeds still holding, Sunday at 4 PM on 7156 khz, and Wednesdays at 9 PM on 3870 khz. W6HDU is going strong with his KW-1. KG6NH is on with a pair of 3-500's in the final. He also builds his own microphones! Oregon and Washington are coming to life on AM with KA7FFB, W7BIL, AI7Y and W7JKY as anchorman. N6OMW is on with a smooth sounding DX-100. N6BUU does well with a Viking Mobile in the shack. KE7KK/6 uses a HT-37. W6SGJ is on with a 32V2.
W6RNC had a nice eyeball visit from NI6S, the maestro of 1885, who was on a vacation trip. W6PSS is reported to have TVI problems. KG6AB works at a major BC station in L.A. and also is a college instructor in technical AM broadcasting. WB6PGJ is sidetracked on ATV but recently showed up on AM after a long absence. K6HQI was monitored operating mobile on 7295 SSB while traveling through Michigan, in QSO with W8VYZ and K4KYV (on AM, of course).
RESULTS, 40-20-10m AM jAMboree; Another great AM operating EVENT! Lots of AMers were on, but not too many scores reported. W8VYZ "tireless crusader for AM" is once again "top dog" with a whopping 1,150 points! So we know from that that a significant number of stations turned out for this one. Some that participated reported working 10m, so 10m AM indeed WAS there for some, in some places. But we did not get the "wide open" situation we had hoped for. Maybe next year. Significant 10m activity reported by second high scorer, Sam in Alameda CA W6HDU with a gigantic 782 points. Really fine because Sam only worked the jAMboree on one day (Sat Apr 16th). 20m activity which is usually evident in evenings/late afternoons , seemed to go on from about noon Eastern time on thru to band close. W8VYZ reported working an AMer on from the Azores! YES! AM DX IS POSSIBLE! Brand new SPAMer from Colorado, Glenn KB0BHN did a SUPER job operating 40&20 using a Kenwood430 (ricebox, abt 30w!)! A fine score of 656 ! Veteran W2XC, Ray in NY reports increasing AM activity on these bands due to reviving sunspots, his logs showing 17 States/provs on the one day he got on (Sat). Logs are NOT required when reporting a score, BUT are helpful to me in that I can see who/where AMing was. Barry,W7JKY in Oregon reporting in right after another "Veteran" , namely K8MLV/0 none other than Rick in Pueblo CO with 330 points. Barry (7JKY)needs to know "commonly used AM frequencies on VHF " so as to activate on AM in the Portland, Oregon Area. Plans to use a CommunicatorIII on 2m AM. Anyone near Barry can let us know current useage up there? Maybe we could compile a listing of VHF-AM across the USA for assistance for VHF AM mobile ops? Thanks, Barry for the letter - the score of 221 points was VERY GOOD for a Pac-NW (Pacific Northwest) station. WE REALLY APPRECIATE your volunteering to show the "Story of Yea-EM" video to your local ham club. WE NEED MORE AMers from up that way! It was the FIRST AM JABOREE for Gary, KE8JW who had a lot of fun using a Kenwood on AM (low power) on 40m for a fine score of 135 points. He comments on the fine folks he has met on AM . Glad to have you "aboard" Gary! John, W4KYL (No. Lauderdale FL) was only on Sunday morning, says he likes the 3-bander because "40 is good in the morning, 10 in the PM and 20 early eves". A fine score for John of 98 points. Thanks to ALL THESE WINNERS and all those winners that participated but neglected to report in.
IT IS WITH GREAT LOSS : That we note the passing of Don Heukrath, WA2ABK. Don was a tireless worker for AM (see K1KV's article last issue). We first met him on the late-nite weekend sessions on 40m around 1978-79 (7.160) We worked Don on several bands and he was instrumental in helping the SPAM effort, holding the Official office of East Coast Director. He will be greatly missed .
K5FZ(Mike) and WA5VGO(Darrell) and W5TQD(Marvin) GO TO DAYTON: All agreed that "everyone should go, once", BUT "it's way TOO BIG and not enough old stuff was there this year". Marv said it took him five hours to make ONE fleamarket tour. Darrell got a HQ-129 and Mike got some stuff too.
SOME ARE ASKING ABOUT "Houston Bill", WB5UMJ alias Ridley Bibble: He has QRT due to some severe interference problems -BUT- will retire in a couple of yrs. to a "hinterland" QTH free from such problems , etc. You may remember his BIG signal with superb audio "second only to that of K5SWK". Well, Otis(SWK) built BOTH rigs !
LUCKY HAM (MAYBE OF THE YEAR) : WA5VGO got a restorable Ranger(Johnson type) at a local fleamarket recently for $35!
- 73 de WA5TWF
(Names omitted - Past Copy)
FOR SALE: Valiant I $75, Hallicrafters S-76 $35, Drake 2NT novice CW xmtr $40. FOR TRADE: will trade 2 R-390A's - one working, one for parts, both complete, with meters and manual, for a good, working R-388 with manual. Pick up only on all the above.
WANTED: Valiant manual; copy "VHF Horizons" article on "The Ultimate Modulator" (in one of first three issues); copy "Series Overmodulation" article from Dec. 48 "Electronics." Will pay for copying, postage, etc.
NEED: Cable connectors for ART-13.
WANTED: ARRL Radio Amateur Handbooks printed before 1970, also Heath DX-60 transmitter and HG-10 VFO in good condition.
FOR SALE: HQ-170A mint $150. M.C. Jones power meter with coupler $25 (1 KW). 16 hy 450 MA choke Thermador Electric $20. New 866A $3, 3B28 $4, 805 $20, 810 $20, 4D32 $35. Inquire on others. BC-610 modulation transformer, inquire.
WANTED audio transformers U.T.C. LS-49, Chicago BD-2. R-390/URR manual (not R-390A). ALSO WANTED: type 6386 tubes (this is a little dual triode with 9-pin miniature base, a little shorter and "fatter" than a 12AU7, etc.)
WANTED: A pair of 6HF5 tubes, must be unused.
FOR SALE: Hallicrafters HT-4-I transmitter (BC-610-I); complete set of tank coils, grid tuning networks, extra tubes, $250. Collins 51J4 HF general coverage receiver, excellent condition, three mechanical filters $400. Heath kit laboratory model L/C/R bridge $50. Johnson Viking II w/122 VFO $85.
Seagoing radio officers are about to be phased out for satellite communication. Many seamen will die because the S.O.S. on 500 khz is absent. Read about glorious story of "Sparks" thru 20th century in QTC, Sequoia Press.
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Edited and published by Donald Chester, K4KYV
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