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-   -   Intermediate frequency, Question? (https://www.rcuniverse.com/forum/rc-radios-transmitters-receivers-servos-gyros-157/3649706-intermediate-frequency-question.html)

RJConnet 12-13-2005 02:29 PM

Intermediate frequency, Question?
 
Does anybody out there know the exact frequency of the 10 megahertz IF (intermediate frequency) used in most of our dual conversion receivers these days?
I have several Rx crystals marked only in frequency and I'm trying to determine what channel they are. Would appreciate any information I can get. Thanks in advance........RJ

laryboy 12-13-2005 03:20 PM

RE: Intermediate frequency, Question?
 
10.7 mhz

TLH101 12-13-2005 03:43 PM

RE: Intermediate frequency, Question?
 
Here's a chart if that is what you need: http://www.modelaircraft.org/comp/frequency.htm

RJConnet 12-13-2005 06:22 PM

RE: Intermediate frequency, Question?
 
Thanks guys, that's just what I needed[8D][8D]..........RJ

Geistware 12-14-2005 03:05 PM

RE: Intermediate frequency, Question?
 
10.7 mhZ

EloyM 12-15-2005 02:41 AM

RE: Intermediate frequency, Question?
 
10.7 MHz is the IF frequency used in most non-R/C broadcast band receivers, but I have never seen it in an R/C receiver. It could be used of course, but none of the schematics in my collection show it.
Actually, two are used, 10.245 or 11.155 MHz, which determines the "shift" of the receiver.
Look at the soldered in crystal in your receiver, not the plug-in replaceable one. they are generally marked with their frequency.

Geistware 12-15-2005 06:27 AM

RE: Intermediate frequency, Question?
 
This would be 10.7 shifted either positive .455 for JR or negative .455 for Futaba.

ORIGINAL: EloyM

10.7 MHz is the IF frequency used in most non-R/C broadcast band receivers, but I have never seen it in an R/C receiver. It could be used of course, but none of the schematics in my collection show it.
Actually, two are used, 10.245 or 11.155 MHz, which determines the "shift" of the receiver.
Look at the soldered in crystal in your receiver, not the plug-in replaceable one. they are generally marked with their frequency.

CrashGaalaas 12-15-2005 10:57 AM

RE: Intermediate frequency, Question?
 
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.

Mac_Man_UK 12-15-2005 11:57 AM

RE: Intermediate frequency, Question?
 
For the JR DC Receivers, the signal is mixed with 11.155 MHz to give you the 455 KHz 2nd IF.

Geistware 12-15-2005 11:58 AM

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.

RJConnet 12-15-2005 01:10 PM

RE: Intermediate frequency, Question?
 
Anyway, I have a crystal which is marked 61.970H KDS 9C. I think it might be Hitec but i'm not absolutely sure and I am sure that a Hitec crystal will not work in an Airtronics Rx. So I guess I don't know where that leaves me????? I have other Hitec crystals which are marked with the actual channel frequencey[:o][:o].......RJ


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