Another Quick Demo of my “No Tuned Circuit” Direct Conversion Radio

This is a video of me listening to radio Cairo in my basement while working on other projects. The slight drift from zero beat can be heard at the end. This is from the transmitter drifting… not the receiver. I know this because I have looked with a frequency counter and the receiver stability is within a fraction of a Hz. This is really the only drawback of this radio- that you have to zero beat AM. Still it works pretty well as is.

My next step is to go back to quadrature output again and build a simple DSP demodulator out of popcorn 12bit ADC’s and a PIC micro. This way I can listen to AM without zero beating the carrier. This is done by generating two outputs 90 deg out phase, squaring them, summing them and then taking the square root. This gives you the magnitude of the envelope of the carrier or the AM modulation.


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