The Sparton 930 is a type of TRF radio. Sparton called it Equasonne. All the tuning is done up front, usually before any tube amplifiers. Then the signal is fed into a group of 484 or 485 tubes used as an untuned RF amplifier. From there the audio amplifier is fairly standard.
Norm
: I purchased this receiver at a swap meet in good condition. I was wondering what type of receiver it is?
: A TRF!
: The Sparton 930 is a type of TRF radio. Sparton called it Equasonne. All the tuning is done up front, usually before any tube amplifiers. Then the signal is fed into a group of 484 or 485 tubes used as an untuned RF amplifier. From there the audio amplifier is fairly standard.
: Norm
:
: : I purchased this receiver at a swap meet in good condition. I was wondering what type of receiver it is?
: : A TRF!
The 930 was Sparton's bread-and-butter set in 1929. There was a follow-on model in 1930 (the 931), which differed cheiefly by using electrolytic filter capacitors. As Norm has said, this was not truly a TRF, as Sparton was avoiding RCA's licensing by using the "Technidyne" circuit, invented by Lester Jones. Sparks-Withington Co. renamed it "Equasonne". All of Sparton's sets were built this way until about 1931, when they took out an RCA license. The Equasonne RF amplifier is critical for the placement of the type 484 or 485 tubes in it. You cannot substitute 27s for the 484/5 tubes. Sparton shows this in their service notes. The big difference between Sparton models was always the power supply and amplifier, and of course, the cabinet. Sparton always had excellent audio. If you get your set going, and remember to adjust the antenna trimmer for peak performance, It will be an excellent sounding set. In your model, they used a Magnavox dynamic speaker; about the best available at the time. If the outer suspension leather is still intact on it, be sure to give it a good treatment with Lexol, a leather preservative or at least with neatsfoot oil. Both of these are sold in saddlery stores.