80m AM / SSB Receiver from a scrap VEF10
I was given a couple of VEF 10 Russian sets which cover MW, LW and several shortwave bands. I was able to make one good set from the two, but this left me with a more or less complete PCB minus the audio section (as this was shot).
As these sets are very well designed with a seperate oscillator and mixer and a well desgned IF strip with good characteristics, I thought it would be fun the see if a I could make a set to cover the 80m amateur band. I used the 41m coils and added the correct amount of capacitance to bring the oscillator and mixer down to the correct frequencies for 80m. I then added some series capacitance to a dual gang tuning capacitor I had lying around so it would tune 3.5MHz - 3.9MHz. As there was no audio section I simply used a pair of amplified PC speakers I had lying around rather than headphones (although heaphones do work extremely well with it).
I was able to listen to the AM net on 3.615MHz easily with a decent antenna, and was actually quite impressed at the sensitivity of this set. I then decided to knock up a BFO and product detector for SSB reception. I used the MW coil from the set and the correct capacitance to construct a colpitts oscillator BFO at about 470KHz, this then feeds into a two transistor product detector along with the IF signal to give audio. It works extremely well and will resolve both USB/LSB and CW. I have included the circuit of the BFO and product detector for interest and a photo of the 'lash up' which I will probably put in a box at some point.
Its amazing what you can make from 'left overs' - nothing goes to waste here!
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