I believe that some large model aircraft with multiple engines have a 'Flight Engineer' who is entirely responsible for engine management, with his own separate radio system. But that's rather a special case...

Re - I still don't understand why JB needs two RXs in his boat either.
I'm supplying a free shovel Doug (shovel-Doug- get it.😂) The reason I have 2 RXs is that the new compact sound unit has a main power in and a 'throttle' lead to the RX (self contained module with speaker). The 'throttle' lead is Siamesed with the ESC throttle lead then to the RX.
The other unit is a multi function module with a separate speaker, and for the throttle, it has a port for the throttle lead from the RX which then goes out a port in the other end for the ESC throttle lead.
I am using a converted Mode 2 TX (twin throttles) so 1 ESC/sound for STBD is on r/h stick (ex elev) and the Port side is on the left hand stick (ex Thro). If you plug the new unit into port no 3 (throttle ) and the other into the elev channel you get some sort of feedback (even took out the Pos wire,- still does it. Solved by using ch3 on the second RX,
Can you dig it? I didn't get where I am today by not confusing people!!😁
JB

I think this is the type of telephone system that DG was mentioning.
Old school but interesting!
With a little imagination you could operate all sorts of bits a piece.



Martin555.

Re -Would it be possible to fit two RXs's in to a boat,
You could do Martin, but if you switch one RX off, whatever you were controlling with it will stop (ie servo powered radar etc) and you will have no control for throttle/ rudder etc (if they were on that RX)

Thanks Guys,
It is not something that I will be doing, it was only something that was buzzing around in my head.

Martin555.

Those of us with long memories might recall the difference between the words 'channel' and 'function'.

Nowadays a 'channel' is thought of as a stream of information dedicated to a single task - such as working a rudder. That stream carries 'proportional' positioning information, and so can be thought of as carrying a set of theoretically infinite positions between 0% and 100%. If it was not used to position a servo, it might be used to control a 100-position switch, for instance!

In the early days of radio control, we did not have the luxury of multiple channels, each carrying proportional information, sent as a single frame which could be separated out and sent to different servos. We had a signal - it was either on or off. If we wanted to do more than one thing, we had to process the signal ourselves - usually mechanically. One 'channel' meant one signal.

In its basic form we used an 'escapement' - a bit of mechanics which switched its state once every time it was given a signal pulse. So one pulse would move a bi-directional mechanism from neutral to 'right', and the next pulse would move it to 'left'. For model boats quite complex switching systems could created, driven by a single channel. They were like old telephone dials, whereby a 10-position switch could be pulsed round one click at a time. if you combined that with a mechanical delay on each position you could select one action without initiating all the others - if you were quick!

More sophisticated kits had multiple channels - giving one switch for left, and another for right, a third for 'up' and so on. Full control of an aircraft needed 8 channels, and you needed some extra ones to give in-flight trim!

When proportional systems came out the old use of the word 'channel' became redundant - each proportional channel was the equivalent of an infinite number of 'single channels' - and for a while the word 'function' was used. So what would have been a 4-channel transmitter became a 2-function transmitter....

Nowadays we do everything electrically, but it would be possible to create a mechanical device which would give Martin multiple switches
running off a single proportional 'function'....

Exactly Peter👍
With a little ingenuity you can get 16 or more functions out of a 4 or 6 channel set anyway.
Maybe not simultaneously, but who's got 16 or more fingers and thumbs? 😁
Cheers, Doug 😎

Some Tx`s have 16, even 24 channels available for various functions. These can be run off of two receivers as there are 16 separate channels available. All you have to do is to make sure that the receivers are programmed so that one covers 1-8 and the other 9-16 thus no conflict. In the case that Martin is talking about, the Tx would only have 4 channels available so two 4 channel receivers if bound and used together would conflict. This is why only one receiver could be supplied with power at any one time. Cannot think why you would want to do it though as multi channel sets can be purchased relatively cheaply.
Sorry for the novel Colin but it is difficult to explain.

Hi Colin,
No sweat, if we ignore the unnecessary complication of switching from one to t'other😉
What JB seems to have done is to simply fit two RXs which are both powered up.
What you have to remember is that both RXs will react the same way to the TX!
Say you have the throttle on CH1 of RX1.
Then whenever you give gas (perhaps not the best expression for gentlemen of our advanced ages😮) anyway, whatever function is connected to CH1 on RX2 will react simultaneously.
This would have the same effect as simply using a Y cable to activate two functions on one channel of a single RX.
Alles klar Herr Kommissar? 😁

What Martin was pondering was using two independent RXs and switching between them.
As outlined below it could be done but you'd lose 1 Ch from each RX just to do the switching.
Cheers, Doug 😎

How is it possible to get the 2 rx's to work from one tx. Please keep your answer simple, as I am a rc novice over 6 channels.
Cheers Colin.

That's what I was thinking Peter.👍
BUT! It means sacrificing one Ch of each RX to do the switching, via a relay or MOSFET cct.
RX 1 input must latch the cct, other wise it would drop out again as soon as the power switched, and RX 2 would de-latch it. Timing might be critical to stop it 'hunting'.
So you'd only end up with six channels for boat functions anyway.🤔

I still don't understand why JB needs two RXs in his boat either.
What can be so peculiar in a Sound module or it's wiring to necessitate that?
And how does a second RX cure it??
Will have to dig further into that🙄
Cheers, Doug 😎

I think your suggestion would work so long as you switched the power supply between the receivers and they were both bound to the Tx. Both could not have power at the same time.

My frsky Tx can operate 16 channels. This can be done by either fitting two X8R receivers or using 8 channels on one X8R and s-bus with two four channel decoders for the second eight channels. These do not need switching as you can set the transmitter for either 8 or 16 channels. The s-bus channels can be 1-8 or 9-16. My Dusseldorf Fire Boat will use all 16 channels, if I get it right or if I actually complete it.😁

Hypothetical if you only had a four channel TX&RX but you wanted to control eight servos.
Could you fit two four channel RX's so you could use your boat as normal on one RX then stop the boat switch over to the second RX to operate some different functions,then when you Finnish you switch back to the first RX.

Doug,
Thank you for changing my mistake.

Martin555.

HI Martin,
I took the liberty of changing ESCs to RXs (Receivers) to avoid any confusion!😉
Looking forward to the answers - if any!
You can get modules to control all sorts of things via one channel, i.e. one stick or pot.
I first did it myself some 30 years ago by building a four function relay board and used the AUX pot on my old Sanwa Conquest TX.
There are many Nautical modules around providing 8, 16 or even 32 now I believe functions.
Cheers, Doug 😎

I'm not sure exactly what you mean - could you give an example of what you might want to do with more detail?

Do you simply want to install two separate radio systems in one boat and have two radios to control them...?