Actually, most radios have the capability of sending back info. It is called telemetry. Some do the basic battery power level as standard (Graupner for one) and the rest use special, brand specific sensors to send a raft of info including pressure and temperature back to the LCD screen of the radio. Just in the last couple of years, I was racing r/c sailboats and it was important to know how much power was left in the on board battery. A quick look at the screen told me that.
As far as I know (30 years playing with r/c) receivers only worked well with the same brand transmitter, and most won't work at all with another brand. "Spread Spectrum" technology is a description of how 2.4 systems work and all of the 2.4 radios use it. It does not make those radio bits compatible.
Now, admittedly we are talking about very short range here, and the vehicle being controlled is not going to drop from the sky and possibly kill someone. In my experience, the best results are with same brand components.
I do see on the ebay stores, some receivers that say they are xxx compatible. I have no experience with them so I don't know.
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I am guessing (and that is all it is) the FlySky (and generic) 2-4 channel receivers do not include telemetry functions, that it is all one-way communications between the xmtr and rcvr. If that is so the xmtr has no way of knowing what/how many/what type of rcvr it is binding with. If the data and checksum is good the binding will be successful but that is not what MichaelM is experiencing. It may not be the transmitter since it does bind with a rcvr.
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My thinking is that it's very unlikely that both FlySky receivers would be bad. And, after having everything tried at the LHS it certainly appears that I got a bum FlySky transmitter. It binded (bound?) with my very first receiver, and now won't go with any others.
I haven't completely given up on FlySky. I'll probably get another transmitter soon, then I'll know for sure.
Nye, Inyo & Esmeralda Railroad