Talkgroup aliases in SDRTrunk

[kc2klc]

I am successfully decoding several talkgroups in our local P25 system (Broome County, NY) using SDR Trunk 0.5.0-beta5 in Windows 10 and an RTL-SDR. I've set up aliases according to an old thread at SDRTrunk - Labelling Talkgroups, but the names do not show up where I expect them to (somewhere below the waterfall?). I'm attaching screen shots for what I assume are the relevant setup tabs. Any ideas? Thanks!

 

[GTR8000]

You're adding the TGID in the wrong spot. It doesn't go into the Group field (that field is to allow you to form your own groups of talkgroups/radios). You have to go down into the Identifiers section, then add an APCO-25 Talkgroup for each alias.

Btw, since both Broome County cells are simulcast, you want to change the channel definitions from C4FM to LSM. You should also probably have it Ignore Data Calls.

Also, beta6 was released today and contains a fix for channel tuning, so I suggest upgrading the software as well.

 

[kc2klc]

I think I already did that - but I neglected to select an alias to show that. Here is a screen capture of the Identifier field setting. I deleted the numbers from the Group field, but that didn't help. I also tried switching the Modulation between C4FM and LSM, but that had no effect (I don't know which one is the correct one for our system). I guess I could try upgrading, but I suspect that won't fix whatever my problem is. Maybe you (or someone else) can spot something else I missed. I really appreciate the time & effort expended to assist me!

 

[dave3825]

I also tried switching the Modulation between C4FM and LSM, but that had no effect (I don't know which one is the correct one for our system). I guess I could try upgrading, but I suspect that won't fix whatever my problem is.

Like @GTR8000 said, you want LSM for those sites.

Can you post a screenshot of with Now Playing checked on the top window and the Events tab checked on the bottom? Like this?

 

[GTR8000]

Ah, I see what the problem is. You don't have any Alias List assigned to the two Broome channels.

While you obviously need to keep the East and West sites separate, you'll want to create a single alias list for all of Broome County, then assign that alias list to both of the channel definitions.

 

[kc2klc]

Bingo! Didn't notice that pulldown option, nor do I recall it having been mentioned in the thread I referenced. Thanks GTR8000! (I see Broome E signals on the SDR, but SDRTrunk is failing to identify the control channel - perhaps reception is poor in my location near Binghamton airport; for the time being, I'm simply monitoring Broome W.)

 

[GTR8000]

Yeah if you're too far from the East cell you probably won't do well decoding it. Make sure you fiddle with the PPM correction to get it as close to centered (0) as possible, and play with the gain. Also make sure both channels are set to LSM, that makes a difference for simulcast (which Broome is).

 

[kc2klc]

I'm using an RTL-SDR Blog V.3, which has a 1 PPM TCXO. It was my understanding that this eliminated the need to adjust the PPM correction. Am I correct in this assumption?

 

[GTR8000]

The TCXO will keep it from drifting, but you may still need to apply a small amount of initial correction. The dongles are almost never exactly at 0 PPM, in fact I've found that the RTL-SDR.com dongles normally require up to +/- 2.5 PPM of initial correction.

SDRTrunk automatically adjusts the PPM by default, unless you disable it, so it may've already applied the right amount of correction for you.