Junk Box DC Receiver

By Nadisha 4S7NR

This idea of converting a super-heterodyne radio to a DC receiver came to me when I was a SWL. I built this receiver from a Junked cassette radio. For long time I used to listen to our Ham friends on 40m using my Junk Receiver. I learned a lot being a listener during my SWL days. I was able to tuned this simple rcvr from 3 Mhz to above 15 Mhz, covering 80m, 40m, 30m and 20m bands.

If you look at the circuit, it looks like a front end of a broadcast band superhet receiver. It is a BC receiver (you know the type you find on small cassette radios). Suppose if you tune a Superhet receiver to listen 7.0 Mhz. The front end coil and C1A tunes on 7.0 Mhz. The Local Oscillator and C1B tunes on 455 Khz below 7.0 Mhz to produce IF signal 455 Khz. What we do, shift the Oscillator frequency closer to incoming frequency (about 1-2 Khz difference) to get AF.

The L1 is a short wave coil wound on a ferrite rod. T1 is short wave oscillator coil (green can). T2 is an audio driver transformer, not an IF transformer any more. Every thing else should be simple. From the transformer we use sutable audio amplifier to amplify the audio.

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