P25 through allstar?

Hi all,
Very new to allstar, so please bear with me.

I have a 110w Quantar running mixed P25/analog, but mostly P25. I wanted to get better coverage by adding some receive only sites around town and I came across allstar and RTCM as a voting solution, or perhaps including some SHARIs as receiver nodes. I think this could be exactly what I need. However I find very little written about using P25 with allstar, so I assume it’s not something that is natively supported. Could you all provide some more info about this kind of use-case? Has something like this ever been done?


I can’t speak to the RTCM’s but others here will chime in on that.

Primarily your question was about getting P25 to ASL.
The reason you don’t see much about that is it’s on other forums.

Please check-out ‘dvswitch’ that can be added to allstar.

Could you tell me what ASL is? I’m not familiar with that abbreviation.

I’ve been mulling this whole thing over for the past couple days. I feel like if I used the decoded RX audio from actual P25 radios, that would work, but then I wouldn’t have RSSI needed for voting. Is that where the issue stems? My understanding is that the discriminator tap is what allows the node to measure signal strength right?

Sure… it’s getting to be alphabet soup around here anymore.


To put it in my old fashion terms so everyone is on the same page.

our software app_rpt is a module program of sorts residing in a slightly older version of ASTERISK,
a open-source telephony PBX

I think the resent term now used is (with the latest beta) is ‘asl-asterisk’ since our code is far different now then when it was part of the asterisk project. We are kinda on our own tangent now.

So, some folks might refer to ASL as the network that connects us together and some talking about the software. Unfortunate but true.
I have just recently started changing my habits to be on the same page as the group, But I like calling the software app_rpt and the network ASL as it was. It is more clear. Unless you are new to it. LOL
Hope that helps.

Oh duh! ASL is allstarlink LOL. I took ASL to be the term for the network and software package, and app_rpt to be the asterisk plugin, so it sounds like we are on the same page there.

I need to read up on the inner workings of a repeater and figure out the different signals that can go in and out.

It’s OK, I understand the confusion and why I try to be carefull with my terms.

So, Am I to guess that you are wanting to just make a radio connection from a P25 with audio, cos & PTT
Can be done easy enough with a USB Radio Interface (URI)
But if you are going for the voted option, you should be using the RTCM - radio thin client module.
I can’t help there.
But to better understand what you are doing and get use to this,
I suggest you start off with a simple URI node. Get it working that way and you will have a grip for it.


Yeah that’s exactly what I’m trying to do. I want to do voting just to increase my coverage because the repeater has issues picking up HH radios beyond a few miles. I’ll look into the URI node. It would be nice to get a grip on this stuff and get an audio stream in/out of this repeater.

I guess one big question at the moment. I think I would still want to use the internal repeater controller, but my understanding is that the COS signal wouldn’t be the right one if I want to do voting. I think it has to do with the rtcm being able to read RSSI from the repeater. Quantars have an output called RDSTAT which seems to just be an indicator of whether the repeater is squelched or not. I would still need discriminator audio to get RSSI right?

I believe that is right but I don’t use RTCM’s. I think it is all discriminator for RTCM to be the same.
Perhaps @wd8awp or some others will chime in on that. It is xmas so we may wait a bit before someone checks in.
Come back and bump the thread after xmas if no reply on that.
I assume you found the wiki page but here if not…

1 Like

Thanks, yes. I’ll check back in the coming days.

If you use RTCMs for voting, only analog will be voted. Not P25. You can use DVSwitch with a Quantar, but the linking (no voting) will be P25 only. I believe you can link / vote P25 with Motorola equipment ( Motorola Astro-Tac 3000 Comparator) I don’t know if it will link / vote analog.

Yeah I know I can do it with Astro-Tac equipment, but that’ll really break the bank. I also think that those need real leased POTS lines, though I’m sure you could set something up with voip. That’s really unfortunate that ASL or DVSwitch don’t natively support something like this. I also have no idea what I’m doing when it comes to the comparator configuration and all that.

Actually… now that I’m thinking about it, how does voting actually work? In theory, why would voting care if it’s data or voice that’s being voted upon, you know? It’s all still even FM for P25, not QAM or something like that. I don’t know, I imagine I’m missing some important information here as to why it wouldn’t work. Any thoughts?

They don’t have to use leased lines. I believe it can be done over IP. I can’t speak for ASL as far as voting using the Quantar. I can for DVSwitch. DVSwitch for the Quantar, is called “Quantar Bridge” It’s job is quite simple. QB allows a Quantar to be connected to the MMDVM P25 network. That’s all. We don’t do any voting.

RTCM’s only work with analog as others have mentioned. The RTCM needs Quantar discriminator and CTCSS outputs. The RTCM digitizes 80ms of audio into packets, places an RSSI value (from on board squelch circuit) and GPS time on each packet. This gives app_rpt the information it needs to vote. And it does it very well.

App_rpt replaces the Quantar repeater controller in order to perform (not only voting but) all repeater controller and analog linking functions.

It is possible to use DVSwitch for P25 and RTCMs for analog. I and others are doing that very thing.

Thanks for explaining how voting works. That explains why it would never work for digital. The more I’m looking at the astro tac stuff, the more it seems like the best way to do this. No point in reinventing the wheel. Maybe I’ll put some Christmas money into getting a comparator and some RX units. Thanks all, Merry Christmas.

If you are looking for an Astro TAC Comparator, I can probably make you a deal you can’t refuse. I would have to check to confirm, but I should have some that are NOS.

Do your research and see if that is the road that you want to go down.

You would also need to find some Astro TAC receivers too to feed to the comparator.

As others have said, the RTCM won’t do what you want for P25. It needs to slice up raw discriminator audio, digitize it, packetize it, time stamp it, and send it to chan_voter. That is not going to make P25 data very happy when you do that, and there is no way for chan_voter to figure out how to put P25 data packets back together. :slight_smile:


I have spent the past couple days researching using an ATAC comparator and some quantar T5367A receivers with v.24 over IP using some cisco routers. I think this is the route I want to go. You certainly have my attention, so feel free to shoot me a message and we can talk about the comparator. Thanks!