|Click on the above images for enlarged views|
A classic from the first half of the 1930s, the Twinplex is a regenerative receiver using a type 19 dual triode. One half is the regenerative detector and the other is a stage of audio amplification. I built it to replicate in general terms the appearance of this receiver as published in a 1934 issue of Short Wave Craft magazine.
It's just another iteration of the basic Doerle 2-tube circuit. After the 19 was introduced (in 1933, I believe), it became the novelty receiver of 1934 because it used the first-ever dual triode. Note that all components are mounted on the back of the front panel. In fact, the entire receiver is built on a single piece of sheet metal bent at right angles.
The plug-in coils are wound on 'retired' 4-pin tube bases. Note that in place of a filament rheostat I installed an antenna tuning capacitor. The National 'Velvet Vernier' dial makes tuning a pleasure. Performance, although pretty good, would be better if I could put up a longer, higher antenna.