15 Circuits with 8 Conductors

Sixty years ago this month, the August 1965 issue of Popular Mechanics showed how to use only eight conductors to control 15 different circuits. The trick was using three independent power sources. This way, 5+3 wires could be used to make 5×3 circuits. The magazine noted that the most common application would be for signaling.

Advanced students could use this as a science fair project.  The top components could be switches, and the bottom ones could be lamps.  For another way of making wires do double duty, see our earlier post about a mystery device.



1955 One Tube UHF Transceiver

Shown here, in the August 1955 issue of Radio News, is Robert Richardson, W4UCH, operating a 70 cm handheld radio. He noted that there was little activity above 2 meters, and set out to provide an economical way to get on the UHF band. The cost of each transceiver was only $13, meaning that two could be made for about $25. Range was about a mile over favorable terrain, with distances of up to five miles with an outside dipole antenna. The set was billed as ideal for short-range civil defense work.

On transmit, half of the 12AT7 tube was used as modulator, with the other half as oscillator. On receive, the oscillator functioned as a self-quenching superregenerative receiver.

Tuning was accomplished with a temporary Lecher wire made of two wires nailed to a board. A knife or razor blade was moved along the wires until the receiver quieted. The distance between two such points was half the wavelength.



1940 Battery Converter

The young man in this picture is now close to 100 years old, but in 1940, you can see the look of pride in his face that his dad figured out how to economize on the cost of B batteries for their portable radio. Generally, such radios required two batteries–one, often 1.5 volts, for the filaments, and another one, usually 45-90 volts for the B+.

But here, Dad purchased a converter which allowed him to run the radio from a single 6-volt battery. The power supply, apparently manufactured by Electro Products Co., 549 W. Randolph, Chicago, produced all of the necessary voltages. It could be used, as shown here, with a dry cell battery. Or, it could be used in the car, where an external antenna might also be required.

The picture appeared in the August 1940 issue of Popular Mechanics.



1945 One-Tube Regen

Eighty years ago this month, this schematic for a one-tube regenerative receiver appeared in the August 1945 issue of QST.  It used a 3A5 dual triode, half of which served as detector, with the other half being the AF amplifier.  The use of midget parts allowed the set to be built in a metal case measuring only 4 x 5 x 3 inches.

It appeared in Hints and Kinks, where it had been sent in by Charles Richardson, W8RXY. He reported that two plug-in coils were used to cover 16 through 70 meters. He used it to drive a small speaker, but it could also be used with headphones. He noted that when he was located in England, the set pulled in the States as well as the Orient.



1940 Radio Controlled Airplane

This young woman is now close to 90 years old, but she is shown here, on the cover of QST for August 1940, inspecting a radio controlled aircraft. The accompanying article by Clarence E. Bohnenblust, W9PEP, (probably her father) describes the radio controls. He was approached some time earlier by one C.H. Siegfried, who designed and constructed the gasoline-powered airplane, with a request to design radio control gear. For a transmitter, a 20-watt five meter unit was used. Onboard the aircraft, the superregenerative receiver shown here was used, and could reliably pick up the signal a mile away.

It was determined that four controls were necessary: rudder left and right, elevators up and down, motor speed high or low, and motor shut off. This was accomplished with an elaborate system of cams, operated by a pulsed signal from the transmitter. For pulses, an ordinary telephone dial was used. Each pulse moved the cams one notch, and they were held in place as long as the carrier was received. When the carrier was cut, it reset to a neutral position, ready fpr the next command.

The magazine notes that the airplane was successfully demonstrated at the ARRL Midwest Division Convention in Wichita in April, and was going to be seen again at the ARRL National Convention in Chicago later that year.



Silent TV for the Kids, 1955

These young men have been collecting Social Security for over a decade now, but 70 years ago, they were watching television while their mother and a friend chatted in the same room, undisturbed by the noisy program. You could do it yourself by following the instructions in the August 1955 issue of Popular Mechanics. You installed a remote listening device, similar to the one we recently highlighted, which allowed you to switch off the speaker and route the audio to headphones.

But according to the article, you could “make a big hit with the kids” by installing the headphones inside space helmets, available at toy stores.



Texas Girl Builds Radio: 1925

Shown here a hundred years ago today, in the August 9, 1925, issue of the San Antonio (TX) Light is Miss Annie Bommer of 312 Frasch Street, San Antonio.

Even though she was still in her teens, she thought nothing of building this five-tube TRF receiver with a regenerative detector.

She had three years experience in radio, starting with a crystal set, and had worked her way up to more complex sets. She was also skilled at automobile mechanics, the result of chumming around with her brothers. She had been put in charge of the radio department at Grant’s Department Store and the size of the department had greatly increased under her management.



Transatlantic Portable Contact, 1925

As most readers of this site already know, one of my interests in amateur radio is portable operating, through activities such as Field Day, Parks on the Air, and World Wide Flora and Fauna. It’s fun to go to just about any spot on earth, and know that within a short time, I can be sending signals around the world. While most of my contacts wind up being domestic, there is always still a bit of a thrill when my signal hops the Pond.

And that excitement is nothing new, as shown by this ad in Popular Wireless a hundred years ago today, August 8, 1925. It recounts the recent field gathering of the Golders Green and Hendon Radio Society (assisted by the Hounslow and Inland Revenue Radio Societes) at which communications with the United States was first effected using portable apparatus.

To make this happen, the valves (what Americans would call vacuum tubes) bore the Marconi and Osram brand.

You can read more about this historic contact in the New York Times for June 8, 1925.



1965 3 Transistor Regen

Sixty years ago this month, the August 1965 issue of Radio-TV Experimenter carried the plans for this three-transistor shortwave regenerative receiver. The parts would set you back only $14, and the completed set was said to be the size of a QSL card.  As shown here, it covered 4-15 MHz, although it could be modified to cover any range between 500 kHz and 30 MHz.  Even a beginner could have it together in about 8 hours.

The set called for a 50 foot antenna and high impedance headphones, although on strong signals, a speaker could be used, in conjunction with a matching transformer.



Swellest Tent in Camp: 1925

One hundred years ago, these young men had the swellest tent in camp, that’s to a little bit of ingenuity and some Eveready dry cells.  In addition to the batteries, they just needed a little bit of wire, a switch, a socket, a bulb, and maybe a discarded reflector from a car.

They kept giving reliable light, night after night, and that was swell.  The ad appeared in the August 1925 issue of Boys’ Life.