Batboard

I am looking for details on the algorithm used in Astro trunked smartnet or smartzone portables and mobiles that decides when to switch sites. I am also trying to find out if the RSSI is picked off of the AGC or if it is taken from some other place in the circuitry.

I believe there's a field under the trunked main menu where you set values for signal levels in this case. I think the menu is/was called SZ ENV or similar.

Not sure that helps, but it's where you define the levels the radio uses to determine when to switch.

-W

You can alter the settings there, but the values it shows in that screen do not correspond to the RSSI values you see on the radio display when you push the "site" button. For instance, the "acceptable", "good", and "excellent" thresholds are factory set at 34, 40, & 46 respectively in an XTS3000. Any RSSI below 34 is considered "poor". In actuality, you need close to an "80" on the screen to consider a site "excellent". It will work poorly in the 50's & hardly at all in the 40's.

As far as the criteria for switching, I know this much:

The radio will switch from a "poor" site to any of the other levels.
It will switch from "acceptable" to an "excellent" site, but not from "acceptable" to "good".
It will not switch from a "good" site at all.
This is done to minimize constant site switching. As for the actual algorithm involved, that I don't know.

Todd

Here's what I found so far.
1) when all control and adjacent control channel signals are "poor" the radio selects the strongest signal.
2) When the current control channel is above "poor", the signal must transition two levels for the radio to change. for example if the control channel is at "acceptable" an adjacent site control channel must be "excelent" in order to initiate a change.
This seems to explain the unusual behavior we are seeing with radio's appearing to hang on sites longer than expected.

Good to hear your results reflect what I've been told.

Todd