Thursday, July 12, 2018

2 transistor radio in sim

The circuit asked about
The sim. I added C3 and R4 so I could read the output with a zero reference. .1mv in 5mv out. The transformer is step down so the output current level is higher with the lower voltage. Chances are the loading produced by a mismatch would not produce the same output level without the transformer. food for thought? (maybe another sim should be ran with RC coupling?)


  1. the reception coil as I think is not conected withe bas and emeter of the first transitor


  2. excuse me I have make mistake in the precedante commen . the reception coil as I think is not coretly conected withe the base and emeter of the first transitor

  3. Wow! That was a while ago. It was an answer to a question posted on a radio board. The circuit is from the GE transistor manual and the poster question how it could work.
    It is not optimum but it works by using the transistor junction as the detector. The input is a modulated AM signal. The output from the first stage is a series of pulses the same as if a diode was used. The output transformer forms the audio by filtering the RF pulse into AF. The second stage amplifies the AF to drive the headphone.

  4. Imagine a relay with the emitter base being the coil and the collector as the switch contact connecting the battery to the transformer.

    The transformer will receive a series of pulses.

    The reactance of the transformer will not allow it to respond fast enough to pass RF.

    The RF pulse are shaped into AF.

    Stage 2 amplifies the AF.