I am using three repeaters in Motorola IPSC with same frequency (sic) 😲

Question (edited):

I am using three repeaters in Motorola IPSC with same frequency and different color codes. Distance between each repeaters 1 and 2 is 40 km by road. Repeater 2 and 3 are 30km apart. All are connected through microwave link. 

When a call initiated from repeater 3, the call is received on repeater 2 but not on Repeater 1. The same problem is observed when a call is initiated from Repeater 1: Repeater 2 receives the signal but noth is received on Repeater 3.

Can you please advice what are the levels to be maintained in Repeater RSSI and Beacon intervals. Both repeaters slots are in wide area.

Answer:

It is currently not possible to operate an IPSC system with repeaters on the same frequency with coverage overlap.

You can reuse the same frequency pair on adjoining RF sites, if there is no (or very negligible) overlap. In such cases, you need to be careful to design the system such that the transmission from a radio is not received by more than one repeater at a sufficient level so as to create self-interference.

For instances where the radio transmission can be received by another site, you can try raising the RSSI threshold on one or both repeaters but this will have mixed results. There is no recommended level or any means to choose a level in this specific case.

Adjusting the beacon timing will not have any (direct) impact. At best, you could get the radio to roam sooner when the user moves between the areas covered by different sites - which might prevent the radio sticking to one of the sites.

Another possibility would be to reduce the TX power on some, or all, of the repeaters such that the outbound overlap is minimised. Similarly, you could use an antenna with a radiation pattern that would allow you to direct the signal away from the adjacent RF site.

At the moment, the solution would be to use one RF site for TX & RX and use the other two for RX only then configure the repeaters for Digital Voting. The TX & RX RF site would be the one that provides the best - or total area - coverage.

The most obvious solution would be to use different frequencies. The other option would be to use simulcast but that's something else...