If you can make it work with ZCs, you will have people approaching you with business propositions.
Thank you again. I have a new and different idea. It has to do with phase not amplitude. A low pass filter produces a 90 degree phase shift when its output decreases by 1/2. I will make a filter for 1000 HZ and another for 800 HZ and compare the phase shift between the signal coming from each. It might work. Sorry for the off topic stuff. I will be quiet until results are obtained. Frank
