Interference or what?

I had a bizzare experience today. I was testing a simple band pass filter in the lab. I had connected the output to a speaker. As I was setting up the ckt for testing, I hear the local FM station in the speaker. I was loud and clear. I couldn't believe it. How can that happen. The FM station's antenna is very close to my lab, but that doesn't explain how the FM signal got demodulated and got onto my speaker. Any explanations as to what might have happened? Or any one with a similar experience?

Magnetra

Look at the FM demodulatores. In this circuits, at first FM signal diferentated by mean of a RC circuit and then a push detector is used for extraction of signal from the amplitude. So you must search for such procedure in your setup.
regards

Yea that could be the explanation. My ckt had lots of RC combination. So that might have worked as demodulator.