At 4/21/2007 14:55, you wrote: >Cheep Service Monitor - Take a receiver and an oscilloscope and calibrate >the scope to measure transmitter deviation.
This doesn't quite work. The reason is that the IF filters in NBFM receivers lop off a bit of the incoming signal, resulting in an inaccurate deviation measurement. To get around this, you can replace the 455 kHz final IF filter with a coupling capacitor. I did this with an old, expendable Regency M100 scanner. The IF passband widens to ~30 kHz or so, which is enough to pass all of the NBFM signal to be measured. Now you know why the IF filtering in your service monitor seems a bit wider than your radio. Bob NO6B
