OP25 in Simulcast situations

[wbswetnam]

I can't believe that a dummy like me was able to get OP25 to work on my Linux Ubuntu computer, but it works great! My latest toy!

My question is, how does OP25 do in simulcast situations? Fortunately for me, I live in a semi-rural area that does not yet have simulcast, but I'm curious how about other's experiences with reception of P25 simulcast using OP25. Thanks!

 

[sallen07]

My question is, how does OP25 do in simulcast situations?

I think it's a "your mileage may vary" thing, but it does VERY well on our local Harris P25 simulcast system. Not quite as good as my SDS100, but far better than any other scanner I've tried (BCD325P2, BCD436HP, BCD996P2, PRO-668).

 

[wbswetnam]

Recently I was in Little Rock, and my BCD436HP only did so-so on the Little Rock simulcast. I'm certain that I missed a LOT of traffic, it was silent a lot of the time. I'm going to install Ubuntu on one of my laptops, and then install OP25 configured for the Little Rock simulcast system.

 

[boatbod]

It works great for me on simulcast when using the default qpsk modulation.

 

[Dufus]

OP25 works great for me in Louisiana, St Tammany Parish simulcast.

 

[simpilo]

Still waiting on Oklahoma City to cut-over to APCO P25 PII TDMA ti see how simulcast is on my copy of OP25. Another P25 system here has a few active talk groups OP25 deocdes really well near perfect decodes. Sometimes I get a burst of a screeching sound. Don't know why.

 

[boatbod]

Sometimes I get a burst of a screeching sound. Don't know why.

Could be encrypted traffic? Have you set the --nocrypt parameter?

 

[rivardj]

I have OP25 running on a Raspberry Pi 3 B+ and it seems to handle simulcast fine. I was mobile with my Pi that has a 3.5 inch display on it listening to multiple Detroit area simulcast sites.

 

[simpilo]

Could be encrypted traffic? Have you set the --nocrypt parameter?

Its in the open P25 voice. the screeching is mid-transmission. doesn't happen all the time. Encryption is more like garbled not screeching.

./rx.py --nocrypt --args "rtl" --gains 'lna:24' -S 960000 -q 0 -d 0 -v 1 -2 -V -U -T ecoecn1.tsv 2> stderr.2

 

[fredva]

Works great on simulcast for me with the proper demodulation. The need for something to handle simulcast better than my 436hp or WS-1080 was why I started using OP25.

 

[sqlgeek]

The system that I have set up is OP25 on Ubuntu monitoring a local P25 Phase 2. On the RR database it shows that all 7 frequencies are control and shows Simulcast under the name. The frequency I put into the trunk.tsv file is the current random control frequency that I figured out using GQRX - it actually changed from one the previous day but has been on this one for 4 days in a row.

Ultimately I would like to have this particular system configured to stream to broadcastify since it is currently not available there now. I am trying to figure out how I guarantee that when the control channel changes that I won't have to go in and switch the frequency in the trunk.tsv file. Is this a normal situation and what can I do to make it work with my setup?

 

[gofasters4]

In your trunk.tsv's "control channel list" field, enter all the control frequencies, separated by commas. OP25 will rotate through the list for another control channel if the current one is lost.

 

[fredva]

The system that I have set up is OP25 on Ubuntu monitoring a local P25 Phase 2. On the RR database it shows that all 7 frequencies are control and shows Simulcast under the name. The frequency I put into the trunk.tsv file is the current random control frequency that I figured out using GQRX - it actually changed from one the previous day but has been on this one for 4 days in a row.

Ultimately I would like to have this particular system configured to stream to broadcastify since it is currently not available there now. I am trying to figure out how I guarantee that when the control channel changes that I won't have to go in and switch the frequency in the trunk.tsv file. Is this a normal situation and what can I do to make it work with my setup?

That sounds like it might be a Harris system, where the control channel regularly rotates among several, if not all, of the frequencies in the system. gofasters4 is correct - go ahead and enter all of the system frequencies and you should be good to go.

 

[boatbod]

That sounds like it might be a Harris system, where the control channel regularly rotates among several, if not all, of the frequencies in the system. gofasters4 is correct - go ahead and enter all of the system frequencies and you should be good to go.

This is correct. Make a comma separated list of possible control channel frequencies on one line in trunk.tsv and op25 will cycle through them until is lands on an active control channel. The only downside is that it may take several seconds to acquire the CC because it has to listen to each before it finds the right one. If there is any bias towards some channels being used more often than others, put them in the list first.

 

[gofasters4]

This is correct.[...]

boatbod, thank you for continually making improvements to op25.

 

[maus92]

This is correct. Make a comma separated list of possible control channel frequencies on one line in trunk.tsv and op25 will cycle through them until is lands on an active control channel. The only downside is that it may take several seconds to acquire the CC because it has to listen to each before it finds the right one. If there is any bias towards some channels being used more often than others, put them in the list first.

Does OP25 "lock" the active / current cch until it is lost, or does it continuously scan the cch list?

 

[boatbod]

Does OP25 "lock" the active / current cch until it is lost, or does it continuously scan the cch list?

The answer to that depends on how you configure things

If you put all the control channels in one system (i.e. comma separated on one line) then op25 uses/reuses that CC until it is lost, then it moves to the next one. The NAC value will be the same for all control channels, or you can specify 0 and op25 will use whatever NAC it sees when it finds a control channel. The latter mode can be used quite successfully for roaming.

If on the other hand you create multiple systems (i.e. one frequency per line), op25 cycles to next control channel after a 2 second pause. The NAC value for each system has to be configured differently, and none of them can be 0.

 

[maus92]

The answer to that depends on how you configure things

If you put all the control channels in one system (i.e. comma separated on one line) then op25 uses/reuses that CC until it is lost, then it moves to the next one. The NAC value will be the same for all control channels, or you can specify 0 and op25 will use whatever NAC it sees when it finds a control channel. The latter mode can be used quite successfully for roaming.

If on the other hand you create multiple systems (i.e. one frequency per line), op25 cycles to next control channel after a 2 second pause. The NAC value for each system has to be configured differently, and none of them can be 0.

Not that I monitor a Harris P25 system from a static location, but if I did, I'm assuming the correct configuration would be to have all system freqs listed and comma separated on one line. The usual cch freq would be listed first, with the remaining channels listed in order of preference, if any. If I am understanding you correctly, OP25 would use the first cch in the list until it loses cch data (for x number of seconds,) then moves to the next freq with cch data, and uses that until the cch changes again?

 

[boatbod]

Not that I monitor a Harris P25 system from a static location, but if I did, I'm assuming the correct configuration would be to have all system freqs listed and comma separated on one line. The usual cch freq would be listed first, with the remaining channels listed in order of preference, if any. If I am understanding you correctly, OP25 would use the first cch in the list until it loses cch data (for x number of seconds,) then moves to the next freq with cch data, and uses that until the cch changes again?

You got it.