General Transmitter to Receiver Issues JR421 tx to R700 rx

dragon-chess

New Member
I am running a old JR XF421EX to a JR R700. I cannot seem to get them to communicate. I have channel 33 crystals in both which are new. Is there a programming step I am missing to connect the data streams? Are these products compatible?
 

Slobberdog

Well-Known Member
Have you selected which type of feed it is in the tx, if my memory serves me you have to select ppm or PCM
 

Tony

Staff member
The Rx is 72Mhz, but the Tx is showing to be 3 different Mhz. Make sure you are on 72 and that your crystals that are in there are also rated for 72.

On a side note though, don't use this Tx. Interference like crazy!!!
 

dragon-chess

New Member
Went to local hobby shop with my setup took a little bit till the gentlemen asked me if I put the TX crystal in the TX and the RX in the RX... didnt know they were different so i never looked. Remote is up and running. I plan on getting a 2.4GHz system in the future but this is my first plane and first build. Dont wanna invest too much just yet. Thank you again.
 

Tony

Staff member
Ah yes, forgot to post that lol. It's been a few years since I have had to mess with crystals. Glad you got it going though.
 

Mulder62

New Member
R700 have no crystal says 35 mhz but do not link with XF 421 transmitter. Apparently they must be synthesised. Is there a link button on XF421?
 

RandyDSok

Well-Known Member
R700 have no crystal says 35 mhz but do not link with XF 421 transmitter. Apparently they must be synthesised. Is there a link button on XF421?

These older transmitter and receivers do not use a link or anything like that. They are old school... They have various Mhz bands that they are made to work within and channels within those bands typically using crystal sets or a synthesized frequency. Many are also available in AM or FM radio types ( the ones you mentioned, are FM types ). Because of all of that, the electronics also require that they are tuned for those so they work properly.

So the R700 you listed is using the 35 Mhz frequency... look to see if it also lists the channel it is setup for. The transmitter must also be using the same as the receiver ( or visa versa ) in order that it is compatible. To change the frequency and channels, in the old days you'd send the transmitter and/or receiver into the manufacturer or a properly licensed radio technician to change these and then tune them to work within the new frequency and channel. I suspect the labor charge you'd be charged would exceed the value of the set.
 

Mulder62

New Member
These older transmitter and receivers do not use a link or anything like that. They are old school... They have various Mhz bands that they are made to work within and channels within those bands typically using crystal sets or a synthesized frequency. Many are also available in AM or FM radio types ( the ones you mentioned, are FM types ). Because of all of that, the electronics also require that they are tuned for those so they work properly.

So the R700 you listed is using the 35 Mhz frequency... look to see if it also lists the channel it is setup for. The transmitter must also be using the same as the receiver ( or visa versa ) in order that it is compatible. To change the frequency and channels, in the old days you'd send the transmitter and/or receiver into the manufacturer or a properly licensed radio technician to change these and then tune them to work within the new frequency and channel. I suspect the labor charge you'd be charged would exceed the value of the set.
Thank you
 
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