Found this interesting article about turning a #batdetector circuit into a #directconversion #receiver. It uses the #CD2003 radio chip.
I happen to have this very same bat detector so it is interesting to see how it works. Normally it mixes down signals from an ultrasonic transducer but it does that just as well with radio signals from an antenna 😋

http://www.elektronik-labor.de/HF/DirektMixer2.html