QST, October 1944.

At OneTubeRadio.com, we’e always looking for one tube radios, and seventy years ago, QST carried these circuits for a one-tube AM transceiver for VHF. Since the war had Amateur Radio shut down for the duration, this circuit was designed for WERS on 112 MHz.

The design also took wartime parts shortages into account, since the radio has about the bare number of parts possible to make a functioning transceiver. The author notes that almost any receiving tube can be used, and includes two circuit diagrams, one showing a directly cathode, and one with a separate cathode and filament. A prototype of the unit is shown, built in a cigar box. The antenna, a quarter-wave zepp, plugs into the top of the radio.  (These days, a vertical zepp for VHF is better known as the J-pole.)

The circuit is basically a regenerative receiver, with a carbon microphone controlling current to the cathode. While the modulation percentage is low, the author calls it entirely adequate for short-haul work.

The author recommends a 6J5 tube for the circuit with a cathode, or a 1LE3 or 1G4 for the filament-only circuit, but almost any tube will work. The author does not offer any details as to performance (since he probably wasn’t able to test it on the air during the war). But he notes that “for a transceiver which costs only two dollars or less, as this one does, any attainable range should be satisfactory.”

It’s doubtful whether this simple circuit would meet the current FCC spectral purity requirements for use on the ham bands. After all, even while receiving, the regenerative receiver is radiating. However, if some attention is paid, it’s likely that this circuit would be legal on 49.82 – 49.90 MHz, under sections 15.235 and 15.23 of the FCC rules.

Interestingly, this isn’t the first time that the author of this article has been mentioned at this site. The QST article was written by Gurdon Abell, W2IXK. It appears that he later moved to Connecticut and was licensed as K1EHG after the war.  He passed away in 1999 at the age of 82.  He was mentioned here in an earlier post, and it wouldn’t be incorrect to say that he was the discoverer of meteor scatter communications on VHF.

You can find the original article and a few corrections on the ARRL website. To view these QST articles, you need to be logged in to your ARRL account.

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VHF Antenna at FCC Allegan, Michigan, monitoring station, 1944.

Seventy years ago, the November 1944 issue of Radio News carried a story of a phenomenon that was baffling radio engineers, and was under investigation by the FCC monitoring station at Allegan, Michigan. The station was reporting strange bursts from distant FM broadcast stations, then operating in the 42-50 MHz band. The FCC station had receivers tuned to the frequencies of distant stations, constantly making a record of the signal strengths as the distant stations came up out of the noise. The signals were bursts of a very short duration in the station’s signal strength. These bursts were rarely of a duration longer than a single spoken word or one or two notes of music.

The bursts have been observed at distances of up to 1400 miles, but were more common at distances of 300-700 miles.

The article was almost certainly describing meteor scatter.  A letter to the editor of QST, November 1946, from Gurdon R. Abell, Jr., W2IXK, seems to be the first reference by a ham to the same phenomenon. He noted hearing bursts of signals during the Perseids meteor showers on 144 MHz, which coincided with bursts from New York HF stations inside his skip zone. He concludes, “if this observation can be relied upon, it means that 144-Mc. signals can be refracted by the stronger meteor trails,” and he seeks further corroborating evidence.

This letter was probably inspired by a January 1946 QST article by Oswald G. Villard, Jr., W6QYT.  Villard detailed how to listen to meteors by monitoring short wave stations on 11, 15, or 18 MHz. A meteor would result in a signal being reflected, but with a doppler shift causing a change in frenquency. The two signals would result in a heterodyne, causing an audible whistle.  Villard followed up with another article in QST for July 1947,  but was still focused on the HF effects of meteors, the highest frequency investigated being 27 MHz.

Two follow-up letters to W2IXK’s appeared in QST in January 1947, from Villard, and also from Bruce Henke, W6TFJ, who noted a similar phenomenon on 10 meters. In April 1953, Villard, along with Allen Peterson, W6POH, wrote an article discussing the possibility of using “meteor scatter” for communications on 15 and 20 meters.

Between 1953 and 1956, VHF operators started to figure out the possibilities of this propagation mode. Many of these are detailed in the World Above 50 Mc column in October 1956.

With digital modes, able to make an entire exchange in less than a second, meteor scatter is now fairly routine. In the 1950’s, it required fast Morse code, and more than a little luck. It’s not impossible, however, with voice modes. From Minnesota, South Dakota is a difficult catch on 10 meters, since it’s well within the skip zone. I have South Dakota confirmed, and I’m pretty certain it’s courtesy of a meteor. During a 10 meter contest, I just happened to have the VFO on the frequency being run by W0SD in Salem, SD, a distance of 225 miles. (If you’re driving I-90 through South Dakota and wonder what those towers are as you pass Salem, now you know.)  He was calling CQ, and he came up out of the noise with a booming signal. I quickly called, we made the exchange, and then he disappeared. He was audible for only a few seconds, and it was dumb luck that I was on his frequency for those seconds. I can’t think of any explanation other than meteor scatter for this contact.

Note:  To view the QST articles linked above, you need to be logged in to your ARRL account.

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Fifty years ago this month, November 1964, Electronics Illustrated reviewed Allied Radio’s Knight-Kit Star Roamer Receiver.  I never had one, but this basic receiver was ubiquitous in the 1960’s and 1970’s, and many SWL’s got their start with the four-tube receiver.

According to the magazine, the kit sold for $39.95 and took about 20 hours to build.  The receiver’s low tube count was courtesy of a selenium rectifier and solid-state diode detector.  The radio did receive CW, but without a BFO.  The final IF stage was designed so that it could break into oscillation, making the receiver quasi-regenerative.  Interestingly, the radio included a key jack, since the oscillating stage could be used as a code practice oscillator for an aspiring novice to work on learning the code.

The receiver tuned 200 kHz to 30 MHz, but as the review points out, the longwave band was almost useless, and the overall performance left a lot to be desired.  But in an environment filled with strong shortwave signals, even a simple receiver like this one would give hours of interesting listening to the new SWL.

Good specimens seem to go for about $50 on eBay.  But if you’re in the market, there’s really no sense in getting a working one.  The simple receiver is easy to work on, and the full assembly manual is readily available.  This receiver would be a good candidate to “re-kit”: Take it apart, and keep the mechanical parts, IF transformers, and variable capacitors.  Then,  replace the resistors and capacitors with modern replacements.  The selenium rectifier is probably best replaced with a more modern silicon rectifier.  The old tubes are almost certainly good, and even if they are not, they are all easily obtainable as “new old stock.”  Finally, put it back together according to the manual (and the cautions contained in the EI review).