A very simple direct conversion receiver based on the NE602 Gilbert Cell mixer and a LM386 audio amplifier. The circuit is based onthe famoussudden receiver design from the Rev George Dobbs G3RJV many years ago and looks something like this: My implementation removes all the tuned circuit stuff from pins 6 and 7 of the NE612 (NE602 in my circuit) and injects the RF
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generated by the propeller via a blocking capacitor directly into pin 6 to set the receive frequency. Now as you might well imagine, there are a number of problems with playing at RF frequencies with bits of wire lashing all the bits and pieces together stuck into protoboards. For example, I had to move the RF pin as far from the encoder pins as I could in order to not confuse the encoder code. The frequency kept changing on its own until I turned off the RF. There is a fair amount of "hash" in the receiver audio being generated by the LCD controller chip. But as far as a proof-of-concept impelementation, I could not be happier. With this success, I plan to put together a complete(simple)all-band transceiver using a propeller as the controller as well as RF generation component for both the transmitter oscillator as well as the local oscillator for the receiver.
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