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Old 12-15-2005, 11:58 AM
  #10  
Geistware
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Default RE: Intermediate frequency, Question?

Crash,
You are right.
The 0.445mhZ is the data signal that is demodulated from the carrier signal.
The shift is which side of the carrier signal the modulation is performed. (like positive or negative frequency shift)
Most JR receivers are single conversion. They go straight from 72mhZ to 0.445 mhZ. Futaba and Hitec go through 10.7 to get to 0.445 mhZ. It has been a long time since I had FM theory so I am a little rusty on the practical. I still remember the theory and that should never change. A modulate carrier signal is what we used. When decoded, we can do it once (single conversion) or twice (dual conversion)
ORIGINAL: CrashGaalaas

The first IF is 10.7 mHz which is obtained by mixing either 61.530 mHz or 82.930 mHz ( I don't know which) with the incoming channel 22 frequency 72.230 mHz.

The second IF is 455 kHz which is obtained by mixing either 10.245 mHz or 11.155 mHz (again I don't know which) with the 10.700 mHz first IF.

I don't think either of these mixes determines positive or negative shift. I believe the positive/negative shift is part of how the signal is modulated.

Guess its time to disect a receiver and see what really is going on in there.