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Mr.RC-Cam

Adding a Second R/C Rx to the Same R/C Tx.

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I'm prototyping a device that will use a spare channel on the R/C Tx to control an accessory on the video ground station. That is to say, there will be a R/C Rx in the model aircraft and a duplicate R/C Rx at the ground station, both sharing the same Tx. This is a no-brainer on PPM and PCM R/C systems.

But, I understand that there may be trouble doing this on some of the new spread spectrum R/C systems. So I'm looking for advice on what systems (including the FPV long range UHF) are known to be able to share the same Tx with two R/C receivers at the same time.

BTW, there seems to be some misinformation on the net, as usual. For example, I read that this was not possible on a J/R Spektrum system. But I did not have any problems doing it on my DX6 (standard binding worked fine). So I need a bit of help identifying which systems can/can't do it.

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I think any of the systems that are bidirectional will not eg Multiplex. The rest should be ok I would think, interesting!

What do you have in mind? I did it a few years back to release the plane from my catapult from the tx.

Terry

Edited by Terry

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I think any of the systems that are bidirectional will not eg Multiplex. The rest should be ok I would think, interesting!

I'd sure like to know some specific cans and cannots.

What do you have in mind? I did it a few years back to release the plane from my catapult from the tx.

The second receiver will control a ground station feature from a spare channel on the pilot's R/C Tx. At the moment I can't divulge what the feature is; Maybe later this year.

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Futaba FASST and Scherrer UHF are OK from experience, no problem, binding only stores the transmitter's code into the receiver.

EDIT: For some reason I was thinking only of 2.4GHz systems, but I should include Futaba PCM G3 in the common low-MHz bands that also uses a binding code, but supports 2 receivers as well. Not more though, as that system uses a "reversed" system where you enter the receiver's codes into the transmitter, and there are only 2 fields available to do so.

Edited by Kilrah

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Very helpful! Thanks.

I think that some JR/Spektrum Rx's have a Model Match feature that ID's the receiver back to the Tx. Anyone know if this will be an issue for adding a second Rx?

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AFAIK those don't have an uplink, but in addition to transmitting its ID code the transmitter also sends the selected model's name, and the receiver checks that both do match what was present when binding. So if it's the right TX but a different model name it will stay locked. That shouldn't affect dual receiver operation, but someone who has one would be better inclined to give a definitive answer ;)

Edited by Kilrah

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Well that is promising news. I'll try not to get too distracted worrying about this. But it will be a major snag to my feature idea if dual receivers operation becomes difficult to achieve with the popular R/C systems.

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