Cross Band Mobile Repeater Mesh... or Mobile Mess

[Tom Line]

Been puzzling over why a cross band repeater mesh can't work.
Say there's three stations with 2m/440 cross band repeaters. 2 meter xmit at high power, 440 xmit at low power. 440 tone required to recieve.
Seems like when more than one repeater station recieves input on 440, that both will retransmit on 2 meter. Will two or three identical 2 meter signals distort that bad?
Guess it sounds like a recipe for a mess. Could a digital system do this though?

 

[Moleculo]

Whichever transmitter that is closest to the receiving station will have capture effect, meaning it will squash the other signals. Or if they are close to similar strength, it will just sound like two stations at the same time and neither will be intelligible. The local repeater I frequent has A LOT of traffic which often results in stations TX'ing on the input at the same time - usually accidentally, but sometimes there are jammers. You're describing the same type of problem with the setup you're proposing.

 

[brandon7861]

I believe I have a way to do it. For simplicity, I will explain the linking of two sites.

A few important notes first:
1. This will not work for repeaters using a duplexer, but it should be fine for repeaters using antenna separation or a diplexer.
2. The repeater must be able to activate a CTCSS tone during TX based on what receiver picked up the signal. For example, instead of using the transmitter to add the tone, having it added to the audio before getting to the transmitter, but from one receivers audio only, not both.

Take a look at the drawing below. Lets say I key up within range of the red repeater by transmitting on A. The repeater adds a tone to that and sends it to the transmitter and transmits it on C with that tone. The blue repeater picks up signal C with the required tone, but then passes that audio with no tone to its transmitter to be sent out on B. Since there is no tone leaving the blue repeater (because that only happens when locals transmitting on D are received), the red repeater will not key up on the tail end of the blue repeater as it finishes up because it lacks the correct tone.

 

[Tom Line]

(Interesting. I'm going to focus on off the shelf cross band mobiles with single multi band antennas.)
How about this...
3 cross band base stations 144/440
all require tone or code on their 440 input.
Now when multiple base stations pickup input on 440 and rebroadcast it on 144 at the same time, will the signal sound scrambled? It's basically the same signal. Do they add or scramble?

 

[Moleculo]

(Interesting. I'm going to focus on off the shelf cross band mobiles with single multi band antennas.)
How about this...
3 cross band base stations 144/440
all require tone or code on their 440 input.
Now when multiple base stations pickup input on 440 and rebroadcast it on 144 at the same time, will the signal sound scrambled? It's basically the same signal. Do they add or scramble?

If the 3 cross band radios use different tones or DCS codes then it will only open squelch and transmit when it receives the proper tone/code. However, if one cross band is open because someone activated it, it will now "hear" any other station that also keys the input regardless of the tone/code.

 

[Tom Line]

IT'S OFFICIALLY A MESS !!!
More ways exist to not work than I ever dreamed of.
Thanks to folks for bringing up good information.

Dropping the mesh thing. Looks like requiring a tone or code on the 440 input of any cross banded radio would be a good practice.