DMR decoding issue on weak (fading) signals

[iw3row]

ZUM 1.01 board, Arduino DUE, latest firmware and software commits updated 12/06/2017, GM340 radios.

On mobile/portable stations where the signal tends to have fading it happens that a station opens the DMR repeater then the signal is getting low and the repeater stops to decode, then the signal become strong again but the repeater is not decoding it again (even if it goes back to a high and stable level). RX led glows but TX is not activated again. In this situation people keeps talking but they are not received.

I've noticed several times this behaviour during QSO's, but I was unable to register a log.

[ok2it]

I am seeing simillar behaviour with D+Star also. I am thinking that this could be related to overall performance of 12bit ADC compared to ....16bit sndcard, cmx589 etc.

on the other hand, if re-syncing of session (transmission) after its been lost due to fading could be improved then I am up for it by all means. Question is, us, non-coders, how can we help? Specific tests to be had? Logs? Data?

[DL4OCH]

From my personal experience, I've found, that a value around 750 is best. this enables my repeater to decode down to S3. Having levels around 1200, which gives the first results of a 0.0 BER have provided me a deaf repeater. It's getting better and is sometimes over a commercial one

[f4hlv]

Can the "MAX_SYNC_LOST_FRAMES" configuration in "DMRSlotRX.cpp" (https://github.com/g4klx/MMDVM) be the right solution?