We used to call it "slope detection". An AM radio is tuned slightly
off the FM transmitter frequency. The response of the AM circuit is
maximum right at the carrier frequency and falls off as you move away
from it. An FM signal will get detected because it moves up and down
the slope. It's not exactly hifi, but it works. Of course, a nice
digitally tuned receiver will defeat the idea.




RST Engineering wrote:
It is damned near impossible to find a chip that WILL do both.

Jim




"soxinbox" wrote in message
...
"john smith" wrote in message
...

More likely they can receive both FM and AM signals. It is pretty hard to
find cheap radio receiver chips that can't receive both.