Your questions answered: choosing the best Roaming RSSI level

In my post on the radio's roaming RSSI, I gave some ideas on how to set this value, to achieve the best possible user experience, on a IP Site Connect or Linked Capacity Plus system. But how does one determine the optimal RSSI threshold?

There are a few methods:

Method A: Thumb-suck. Otherwise known as trial and error. This generally has a success rate of around 50% and involves entering a value that seems reasonable then trying it out.

Method B: Looking at coverage plots. For ease of representation - and to help explain this - I've drawn three oversimplified coverage plots. In reality, a coverage plot will look something like this.
In the above plot, the coverage from the two sites intersects at -100dBm (within the black rectangle).
In the below plot, this is around -80dBm.
And in this one (below) the RSSI from the three sites intersect at -70dBm.

Method C: Drive testing. The MOTOTRBO Site Survey Tool allows you to a) connect a MOTOTRBO GPS model radio to a PC and record the coordinates and RSSI, in a file that can be plotted on a map or b) record the RSSI and GPS coordinates, of all radios transmitting on a specific repeater, via an IP connection. A real coverage map can therefore be created which gives the most accurate result.

Read more about Roaming RSSI in IPSC here and in LCP here.


  1. Wayne, I was wondering what version of the Site Survey Tool you have? I'm in the US and only have Version 2.00 on MOL, It does not have the option for the inbound survey.

  2. This is version R11.03.03 and was uploaded on 24.10.14. I had a look at the version number isn't listed though the date stamp is 28.03.12.

  3. I'll see what I can do from here to get that updated but perhaps you could give them a call? Nothing like a customer complaint to get things going.

  4. Hi Wayne, quick question: can a MOTOTRBO radio perform a Site Survey in an analog channel? I want to be able to "read" the coverage area of a customer's analog repeater and compare it with mine. Thanks!

    1. The above tool will probably not support logging in analogue mode. I've never tested this but it's worth a try?


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