P25 No Receive Decode Issue

Help with P25 issues
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N8JDM
Posts: 10
Joined: Tue Jan 22, 2019 1:05 am

P25 No Receive Decode Issue

Post by N8JDM » Wed Jan 23, 2019 1:21 am

Hello, looking for some P25 help or wisdom. I'm working with a friend on a series of multi-mode digital repeaters and we're having an identical problem with all of them receiving/decoding P25. All three repeaters (full duplex) are running Pi-Star on a Raspberry Pi3 with a STM32-DVM "Pi-Hat" board from repeater-builder.com. The board is running the latest MMDVM firmware available for the board (FW v20180723 per the Pi-Star dashboard).

The setup works perfectly for D-Star, DMR, and YSF. However there is no success on P25. Whenever the P25 signal is received, the board indicator shows that the squelch is open but the "P25" light to indicate successful P25 decode never lights up. The same thing is experienced on three different systems (all with different RX radios). I don't see anything in any log on the unit that there is a failed decode or anything remotely wrong when the P25 signal is present. I'm not sure how to debug this facet further? Is there some sort of tunable needed to adjust for P25 for a successful decode - perhaps some sort of audio strength adjustment?

Any hints or ideas would be appreciated. Thanks.

N8JDM
Posts: 10
Joined: Tue Jan 22, 2019 1:05 am

Re: P25 No Receive Decode Issue

Post by N8JDM » Wed Jan 23, 2019 5:01 pm

VK4TUX, thanks for the reply. I was looking at P25TXLevel but that seems to be on outbound transmissions to client radios not MMDVM receiving P25. Am I misunderstanding what that item does? Is there a corresponding P25RXLevel?

N8JDM
Posts: 10
Joined: Tue Jan 22, 2019 1:05 am

Re: P25 No Receive Decode Issue

Post by N8JDM » Fri Jan 25, 2019 1:26 am

VK4TUX wrote:
Wed Jan 23, 2019 10:57 pm
In that case I suggest that you do not have your DMR id programmed correctly in the ASTRO id field in each radio.
I assume you have the repeater nodes set public access in pstar config.

Your p25 radio tx will be blocked by the mmdvm until it see's the correct id.
This was exactly it. We weren't expecting to need an ID for local/Parrot. Once the ASTRO ID was filled in and a little tweaking of the P25TXLevel, everything was working with local/Parrot. I would have thought that the P25 decode would start and maybe get an error rather than not decode at all. Bad assumption there. Thanks for your wisdom on this!
VK4TUX wrote:
Wed Jan 23, 2019 10:57 pm
What P25 radio's do you use ? I have all XTL / XTS and APX types to provide programming advice re the id ?
I don't know what the radio is precisely because it's a friend's who does commercial radio professionally and he's trying from his house to my repeater. Would put safe money on it being a Motorola of some type.

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