Monthly Archives: November 2024

1944 One Tube Radio and Phono Oscillators with Hartley Oscillators

1944RadioCraft01One tube radios don’t get much simpler than the one shown here, which appeared in the November 1944 issue of Radio Craft magazine, having been sent in by one Reggie Baker of Miami, Arizona. The circuit was described as a split Hartley with a type 30 tube. It could operate with two dry cell batteries.

Another Hartley oscillator was used in the circuit shown below, a phono oscillator. This circuit used a 6A8 or 12A8 pentagrid converter tube.  It had been sent in to the magazine by Ralph Day of Moncton, N.B., who pointed out that it could also be used as a signal generator, using either phonograph music or an audio oscillator.  It would appear that this is the same person as the Ralph Granville Day named in this 1959 marriage certificate, as the groom’s occupation is described as “T.V. and Radio.” He was born in 1924, which would have made him 20 years old at the time of the magazine submission. He died in California in 2003, and his obituary notes that he served during the war in the Canadian Merchant Navy, and after the war spent several years at sea as a radio operator.

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1944 Instructional Model Telephone

1944NovPracMechEighty years ago, Britain was at war, but that didn’t stop students from building instructional instruments, as shown by these plans for a telephone appearing in the November 1944 issue of Practical Mechanics.

The set was based upon the original telephone of Alexander Graham Bell, and could be built by senior schoolboys in the science room using readily available material. The magazine provided all of the construction details. Two instruments could be used to communicate from one room to another, strictly with sound power. For longer distances, the magazine recommended a carbon microphone with a battery running to the phone.

It could also be used as an extension for a Morse buzzer. All construction could be done with a few simple hand tools. The most delicate part of the operation was spacing the diaphragm just the right distance from the permanent magnet.



1939 Portable Sound System

1939NovPM11939NovPM2Eighty-five years ago, the gentleman shown here spinning the records put his entrepreneurial skills as well as his tech savvy to work with this portable sound system he designed. He is one Fred Dingman, who authored two construction articles about how to build the sound system in the November and December 1939 issues of Popular Mechanics.

He reported that the investment was only about $25, as all parts are inexpensive, and he built the enclosures himself. The finished circuit put out 10 watts of undistorted sound to two 12-inch speakers, meaning that he could provide adequate volume for small halls or outdoors. It was designed as an inexpensive substitute for small dance orchestras, and he had no difficulty obtaining engagements for fraternity and sorority parties, dancing clubs, or lawn gatherings in a middle west university town.

At a reasonable rate, he provided the equipment, operator, and records. For those wishing to follow in his footsteps, the magazine could provide a complete set of blueprints.  The system could also accommodate a microphone.

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