Category Archives: Radio history

1945 FM Phono Oscillator

1945AugPM21945AugPM3The woman shown above, in the August 1945 issue of Popular Mechanics, appears to be tuning in a program on her broadcast radio. But looks are deceiving, and the set actually tunes the prewar FM band, which covered 42-49 MHz.  And she’s not listening to a radio station.  Instead, she’s listening to a record being played by the gentleman at left, who is a few feet away.

Phono oscillators which played records over a standard AM broadcast radio were fairly common, but this one played the records over an FM radio. According to the article, no claim was made that the simple circuit would give absolutely perfect reproduction, but results from the Popular Mechanics laboratory were satisfactory. The set was more a challenge to the experimenter to open up the new field of FM radio.

The whole circuit was remarkably compact, and consisted of a 6C5 triode tube along with a few other components. Even with wartime parts shortages, most of the parts could probably be scrounged up fairly easily. The whole circuit mounted right on the tone arm, which was constructed of hardwood.

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1970 Soviet 8 Transistor Portable

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Fifty years ago, if a young Soviet comrade were ambitious, and perhaps had a better than average access to parts, he or she would be rewarded with this handsome 8 transistor superheterodyne radio that covered longwave, medium wave, and shortwave broadcast bands.

The plans appeared fifty years ago this month in the August 1970 issue of
Юный техник (Young Technician) magazine.

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1960 British 5 Tube P.A. Amplifier

1960AugPracWirelessCoverSixty years ago this month, the August 1960 issue of the British Practical Wireless magazine carried the plans for this handsome five-tube public address amplifier. The guiding principles behind the design were reliability, portability, and economy. It put out 10-12 watts at modest cost and weight. The built-in speaker was said to provide for dance music in a medium size hall, and in the open air, with reliable speakers, speech would be intelligible about 500 yards.

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1940 Portables

1940AugRadioRetailingEighty years ago, this couple couldn’t decide which portable set they were going to take to the beach, so they decided to take them all. The sets shown originated with RCA Victor, Automatic, Emerson, Sonora, Majestic, and Philco. The picture appeared on the cover of the August 1940 issue of Radio Retailing.



1970 Carrier-Current Remote Speaker

1970AugPMFifty years ago this month, the August 1970 issue of Popular Mechanics showed how to put together this somewhat ambitious project, a remote carrier-current speaker for your hi fi. A one-transistor transmitter was hooked to the output of your amplifier, and the receiver could be plugged in to any outlet in the house to listen remotely. The project also gave you an easy method of having an outdoor speaker, as long as you had an outdoor outlet. If desired, you could construct additional receivers for use in other rooms, all tuned in to the same transmitter. The speakers were equipped with individual volume controls.

To simplify the project, the receiver used a pre-wired audio amplifier available from Lafayette Electronics. The electronics all mounted in a small box that could be affixed to the back of the speaker.

Both transmitter and receiver used a standard 455 kHz IF transformer for their tuned circuit. These were tweaked to get them down to about 400 kHz, the frequency used by the system. That signal was transmitted through the power wiring. This “antenna” was coupled to the circuit on both ends through capacitors.

Transmitter schematic.

Transmitter schematic.

Receiver schematic.

Receiver schematic.



Emergency Hospital Antennas, 1945

1945AugPM5I was a little unclear on the concept when I first saw this illustration in the August 1945 issue of Popular Mechanics, and I suspect that whoever wrote the caption might have been similarly confused.

The caption is “emergency antenna for individual hospital patients,” and is then followed by some details for each of the illustrations. I believe that what they really mean to say was that these were four different ideas for emergency antennas.

I guess I was confused because of the picture on the left. It appears that these wires are to be attached to the antenna terminal of the radio. I was confused because a similar idea, wrapping the radio with wire, can be used to connect an antenna to an external antenna, even though the set doesn’t have an antenna connection. The loop of wire couples inductively to the internal antenna coil. But in this case, the coil of wire apparently is the antenna.

Figure 2 is simply a loop of wire wound around a piece of cardboard and, again, hooked to the radio’s antenna connection. Figure 1 is the same antenna, but cleverly concealed behind a photograph. Figure 4 looks like a lot of work, since it consists of a spider web coil hidden inside the speaker.

It seems to me that a more suitable solution would be to toss a length of wire out the window when the nurse wasn’t looking, although she seems to be very watchful.

 



Popular Mechanics Finds Its Way to Communist China

1950AugPM41947AugPMcoverOur readers enjoy perusing old issues of Popular Mechanics and other magazines, so we understand the excitement of U.S. Marine M/Sgt. Elmer C. Bender in finding the magazine’s August 1947 issue. The flyer, stationed at Tsingtao, China, took off the morning of October 1948 to get in some hours in a training flight.

Due to a faulty fuel gauge, he and Navy Electrician’s Mate William C. Smith were forced to land on a beach only 15 miles from their base, where they were quickly surrounded by Chinese Communists who surmised that they were spies. They were held for over a year until their eventual release.

The two men reported that they weren’t mistreated, but were taken from village to village. Their main problem was boredom, but the Lieutenant charged with their custody would occasionally bring English reading material. The highlight of their stay was when he showed up with the magazine, which both men devoured. Bender reports, in the magazine’s August 1950 issue, that he was especially interested in the issue’s feature on how to solder. When the men were eventually released, the Communist Lieutenant, noting their enthusiasm for the magazine, asked them to send him some more copies upon their return to the U.S.

1947AugPMxmtrWhile there’s no evidence that either man became a ham, it’s likely that they passed many hours reading about the 5-band AM-CW transmitter shown here. When their families got an FM radio, they probably both instinctively knew the trick of placing a folded dipole antenna under a carpet, as shown in the magazine.



A Preview of Postwar Television

1945AugSepNRNWhen this issue of National Radio News, August-September 1945, went to press, the war was still raging in the Pacific. But the end was in sight, and despite the cynicism of skeptics, the editors of the magazine knew that television’s role in the postwar electronic era was a foregone conclusion, “witness the rapt attention of these comely lasses as they view the screen of the General Electric receiver.”