gec: BC 3250; Gecophone

Dear Radio friends,

I just uploaded the circuit diagram op a BC32510, property of the Olens Radiomuseum in Belgium.

I intend to write an article in our magazine, appearing trimestrially.

I would like to receive some explanation about the RF circuit.

Does this type of circuit have a paricular name?

 

Thank you.

 

Georges

 

To thank the Author because you find the post helpful or well done.

Unless there is something strange about the construction it looks like a single tuned radio frequency amplifier with positive feedback (Reaction), thus TRF with reaction. But if carefully adjusted the RF stage can also detect if it's just on the point of oscillation. Depending on HT tap and Grid Bias the 1st or 2nd valve can act as an Anode Bend Detector.

The volume for strong stations is turned down by reduction of gain caused by decreased filament current. The "pot" no doubt about 20 Ohms wirewound.

Det+ might be 48V or 60V tap on a multitap battery (usually every 12V). The +V perhaps 120V via 2500 + 2500 Ohm earphones in series. Grid bias  using a 4.5V or 9V pack (a set of three or six "B" size cells with taps every 1.5V up to -4.5V or -9V). Lead Acid 2V Accumulator for LT.

The next innovation would be to put an RF triode and then later a  tetrode RF tuned preamp in front which as well as improving reception reduced "jamming" if the reaction turned up too high.

To thank the Author because you find the post helpful or well done.