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Multiple Transmitters - 1 Receiver?

#1
Like the subject says, can I bind 2 transmitters to 1 receiver? I'm not trying to buddy box or anything, my wife wants to learn to fly and I'm thinking I can get her film plus a qx7 to practice flying on the Whoop or Gremlin while I fly my 5 inch. I'd like to not have to worry about carrying 2 transmitters if I just want to go bee tv out and fly though. Thoughts? Suggestions?
Forgive me if this has been asked before, I did some googling and searching on Reddit and didn't see anything within the past few years relating.
 
Last edited:

Aslansmonkey

Well-known member
#2
Kind of negates the purpose of binding. In the old days radios worked on frequencies and you simply had to have a receiver that worked on the same frequency. The problem was, if someone else at the field had a transmitter on the same frequency and switched it on, you'd lose control. Radios typically had frequency tags for this reason. You could look around and make sure no one had the same tag as you.

Modern radios work in the same frequency spectrum but only accept commands from the transmitter they are bound to. Binding basically tells the receiver "Hey, only accept this transmitters 'Secret code' and ignore all others." Theoretically the receiver receives signals from whatever is on at the field, but ignores anything that isn't from the transmitter bound to it.

For this reason, you cannot bind two transmitters to the same receiver. It defeats the whole purpose of the binding.

Either rebind her receiver (and rebind it back when you want to use it again) or spring for a new receiver.
 

Merv

Legendary member
#3
...can I bind 2 transmitters to 1 receiver? ...
If I understand your question. You want to fly one aircraft sometimes with one Tx and sometimes with another Tx.

You can do the but you will need to rebind each time you make the switch. Which is no big deal, if you have access the bind plug or button on the Rx. You may need to install a remote bind plug or button to gain access.
 

WillL84

Active member
#4
For this reason, you cannot bind two transmitters to the same receiver. It defeats the whole purpose of the binding.
What about in Flite Test videos where they have multiple receivers connected to a plane for redundancy? Or when they have different control surfaces hooked to different receivers like RamyRC does?
 

luvmy40

Elite member
#5
What about in Flite Test videos where they have multiple receivers connected to a plane for redundancy? Or when they have different control surfaces hooked to different receivers like RamyRC does?
You" should" be able to bind multiple receivers to one transmitter/model if you bind them simultaneously. In theory, that is. I've never tried it.
 

Piotrsko

Master member
#6
@Aslansmonkey has it mostly correct. The transmitter broadcasts a series of data with a marker saying who it is so the receiver responds accordingly. Binding sets that marker in the receiver and gives the reciever a method to reply. Some systems can deal with multiple replies so they can bind more than one reciever. Two receivers bound to a transmitter will mostly always work if you are using only one receiver at one time. Look at all the people who have (sacrilegious) more than one airplane to fly at any given time
 

sprzout

Knower of useless information
Mentor
#7
What about in Flite Test videos where they have multiple receivers connected to a plane for redundancy? Or when they have different control surfaces hooked to different receivers like RamyRC does?
Those receivers for redundancy are usually used in a satellite configuration. Spektrum has that ability, and I have several that have that function; usually they're meant for distance or additional telemetry type of data, so that you're constantly broadcasting and lightening the load from either the main or satellite receiver to the transmitter, or improving the signal.

There may be other brands that offer that; I'm making an assumption that FrSky, Graupner, and Futaba offer that functionality as well, but I don't know for sure since I've never actually dived deep in with those brands of receivers.

To do what the OP wants, though - it's not really possible, at least not with the 2.4Ghz tech. The whole purpose of that tech was to prevent 2 different transmitters from interfering at the same time, and it uses spread spectrum tech to avoid having another transmitter binding to the same receiver. I think really, the only way to achieve what he wants easily, would be to go backwards a bit to 72 mhz and have crystals that match for both receivers.
 

luvmy40

Elite member
#8
I wonder if two receivers could be wired up in parallel? Only the one with it's radio powered would actually do anything? They would both draw power and it would add extra weight but might it not worK? It would be nice if it would work and you could use the tiny micro 4 channel receivers to save weight.

How far off base am I on this?
 

sprzout

Knower of useless information
Mentor
#9
I wonder if two receivers could be wired up in parallel? Only the one with it's radio powered would actually do anything? They would both draw power and it would add extra weight but might it not worK? It would be nice if it would work and you could use the tiny micro 4 channel receivers to save weight.

How far off base am I on this?
Not really. You could put two receivers in the planes, but you'd need to switch the servo and ESC wires between the two. It might be possible to make up your own splitter cables for the servos, but I wouldn't do it, as it might cause power draw issues unless you had a separate battery pack for each receiver, and that's adding weight.
 
#10
You don't need a separate battery pack for each receiver as long as your ESC can supply the needed power. The extra receiver is just one more load. However, if you really want redundancy you would want to use two power sources or you have a single point of failure. No real point in doing this for a small plane.

Also when using DSMX you don't even need to bind all the receivers at the same time.
Note how in the B17 video they bind the four wing receivers and then two tail receivers in two bind cycles.
As they were using six receivers they could have done it one receiver at a time in six bind cycles but because they had extra hands they were able to do it in two steps.
 

Bricks

Master member
#11
I am wondering if this would work, I may have a hard time explaining how thou.
Example RadioMasterTX16s it would take two of them. Bind first radio to channels 1-8 bind second radio to 9-16. Map first radio to use channels 1-8 and second radio map channels 9-16 to the 1-8 channels in the second radio?????????
 
#12
I am wondering if this would work, I may have a hard time explaining how thou.
Example RadioMasterTX16s it would take two of them. Bind first radio to channels 1-8 bind second radio to 9-16. Map first radio to use channels 1-8 and second radio map channels 9-16 to the 1-8 channels in the second radio?????????
Assuming we are using DSMX receivers then no. Each receiver will be running channels 1 - 8. You get redundancy not extra channels. It is more like a high tech wireless Y cable.
 

Bricks

Master member
#13
Assuming we are using DSMX receivers then no. Each receiver will be running channels 1 - 8. You get redundancy not extra channels. It is more like a high tech wireless Y cable.
You would need one 16 channel receiver for the second radio to make channels 9-16 available.. Would not make a difference of protocol as long as the transmitter has 16 channels or more.
 

sprzout

Knower of useless information
Mentor
#14
You don't need a separate battery pack for each receiver as long as your ESC can supply the needed power. The extra receiver is just one more load. However, if you really want redundancy you would want to use two power sources or you have a single point of failure. No real point in doing this for a small plane.

Also when using DSMX you don't even need to bind all the receivers at the same time.
Note how in the B17 video they bind the four wing receivers and then two tail receivers in two bind cycles.
As they were using six receivers they could have done it one receiver at a time in six bind cycles but because they had extra hands they were able to do it in two steps.
I was thinking more that it would be something where he wanted to have two separate receivers connected up, with Y-servo cables going to each servo/ESC, and one end of each Y goes to a port on the receiver. That, in my mind, would be additional load, and for safety, I'd want to have a separate battery pack to power them (or at the very least, the 2nd receiver). Still, all it's buying is redundancy, as you said, and it's not really a satellite receiver connection like you'd have with a Spektrum AR8020T and a remote receiver.
 

luvmy40

Elite member
#15
My idea of two receivers in parallel was so one receiver could be bound to one transmitter and the second receiver could be bound to a second radio.

I THINK this is akin to what the OP wanted in function. I.e., he could take the plane and his radio out to fly today and his wife could the same plane and HER radio out to fly tomorrow with out having swap or re bind the receiver. I may have read the OP wrong though. It's happened before!
 
#16
You would need one 16 channel receiver for the second radio to make channels 9-16 available.. Would not make a difference of protocol as long as the transmitter has 16 channels or more.
Ok I see what you are getting at, use one 8 channel receiver and one 16. In that case you have redundant channels 1-8 and a single coverage for channels 9-16. As long at that matches what you want to do on the airplane side I don't see why it would not work.

I thought you were trying to get a total of 16 channels with two 8 channel receivers and one transmitter. That would not possible without custom software and/or hardware the transmitter.
 
#17
I was thinking more that it would be something where he wanted to have two separate receivers connected up, with Y-servo cables going to each servo/ESC, and one end of each Y goes to a port on the receiver. That, in my mind, would be additional load, and for safety, I'd want to have a separate battery pack to power them (or at the very least, the 2nd receiver).
I don't think that doing what you describe would add any electrical load to the system beyond the power consumed by the extra receiver. You have extra wires but still have the same number of servos doing the same amount of work and the same input voltage.

On the signal wire it may cause an issue if the two receivers are not in perfect sync and the servos are receiving slightly out of sync pulses?
 
#18
My idea of two receivers in parallel was so one receiver could be bound to one transmitter and the second receiver could be bound to a second radio.

I THINK this is akin to what the OP wanted in function. I.e., he could take the plane and his radio out to fly today and his wife could the same plane and HER radio out to fly tomorrow with out having swap or re bind the receiver. I may have read the OP wrong though. It's happened before!
I can't tell what the OP is trying to do. But assuming you are correct a far simpler and faster solution is just use a single receiver and rebind as needed. I don't see why they would need do a rebind more than once at the start of each flying day.
 

LitterBug

Troll Spammer
#19
In openTX world, you can clone a TX/model. It copies over the bind data. If you have a multiprotocol module, this can even be done with DSMX. Not really the safest way to handle sharing a model because at some point, someone could fire up the other TX, and at that point, it's anyone's guess as to which TX will be in control.

I would prefer to bind it to the radio that should be in control.

LB
 
#20
Not sure how you bind a radio receiver to a specific set of channels, however the hardware and signal set says it's possible because the data stream has identifier labels for channels and my understanding of the new tech says it only moves when told to move and has a sort of brake function