SDR Trunk and conventional p25

[kyscan23]

I am using SDR Trunk to monitor a conventional p25 phase 1 channel. The problem I am having is some "calls" will be received with a radio id and talkgroup but a lot do not. The calls that are received with a radio id or talkgroup I can hear and will get streamed. The other calls that are missing the radio id or talkgroup I can not hear and do not stream out. Anyone have and suggestions on how to set the alias for this channel so that any call reguardless if it has a radio id / talkgroup will be heard and streamed out.
Thanks in advance!

 

[dave3825]

What version of Sdrtrunk are you running? How good is your signal and ppm? Poor signal and or ppm can result in poor decodes.

 

[Whiskey3JMC]

Encryption no factor on whatever you're monitoring?

 

[kyscan23]

Encryption no factor on whatever you're monitoring?

No encryption, I'm able to hear the audio on my BCD396XT while I cant hear it with SDRtrunk

 

[kyscan23]

What version of Sdrtrunk are you running? How good is your signal and ppm? Poor signal and or ppm can result in poor decodes.

Version 0.5.3 (final)
Signal peaks at -21
ppm is -1.009 and it is set to auto-adjust

 

[dave3825]

Signal peaks at -21

That's a strong signal. Possible it could be too much? What is the gain set at?

ppm is -1.009 and it is set to auto-adjust

What ppm does it list for the measured error?

 

[Whiskey3JMC]

Also what does your noise floor look like relative to the received signal?

 

[kyscan23]

Does not show a measured error. I am about 1/2 mile from the repeater transmitter.

Is the gain control master what you are referring to that is shown in my screen shot here?

 

[kyscan23]

Also what does your noise floor look like relative to the received signal?

 

[dave3825]

I run 327 on a site I am not super close to. I would try lowering the gain quite a bit. Sometimes too much gain causes decode issues.

 

[kyscan23]

I run 327 on a site I am not super close to. I would try lowering the gain quite a bit. Sometimes too much gain causes decode issues.

I went down to 165 gain and this is what the signal looked like.


While at 165 gain I also got an encrypted call with algorithm unknown showing in the details. I know this site and there is no encryption.


I then went to 0 gain and had no improvement either.

I have noticed that if transmission is over 5 seconds then it is decoded correctly.

What are the thoughts of changing the sample rate? Computer resources not powerful enough?

I also do appreciate you all trying to help me out!

 

[dave3825]

In your tuners tab, is it listing a measured error in ppm yet? What brand dongle are you using ?

 

[kyscan23]

In your tuners tab, is it listing a measured error in ppm yet? What brand dongle are you using ?

no measured error listed
dongle is RTL-SDR.com RTL2832U genuine

 

[dave3825]

no measured error listed

dongle is RTL-SDR.com RTL2832U genuine

In that case, I would set the -1.009 thats there to 0.0. Then uncheck and recheck the "Enable decoder to auto adjust ppm"box. I have never really seen one of those dongles be off more than 0.5 plus or minus.

 

[kyscan23]

In that case, I would set the -1.009 thats there to 0.0. Then uncheck and recheck the "Enable decoder to auto adjust ppm"box. I have never really seen one of those dongles be off more than 0.5 plus or minus.

now shows measured error, still no change in proper decoding though

 

[GTR8000]

The first thing you should do is to remove the Radio ID Range from the "PD" alias. You don't need that, and it could be hosing things up. In fact, get rid of the Talkgroup Range also. The only thing you need for that alias is Talkgroup:1, which is the default for P25 and is rarely ever changed. That's all, keep it simple, TGID 1, nothing else under that alias.

Next, open a new spectrum display from the tuners tab, then lower the gain all the way down to 9 while the channel is active. Watch the peak of the signal and if necessary, slowly raise the gain until you get a nice sharp peak that reaches almost to the top of the spectrum window. You want to keep the gain as low as possible so that the noise floor isn't raised too high, which can drown out the signal you're trying to decode. Less is more, especially if the transmitter is nearby and you have very strong reception.

 

[kyscan23]

The first thing you should do is to remove the Radio ID Range from the "PD" alias. You don't need that, and it could be hosing things up. In fact, get rid of the Talkgroup Range also. The only thing you need for that alias is Talkgroup:1, which is the default for P25 and is rarely ever changed. That's all, keep it simple, TGID 1, nothing else under that alias.

Next, open a new spectrum display from the tuners tab, then lower the gain all the way down to 9 while the channel is active. Watch the peak of the signal and if necessary, slowly raise the gain until you get a nice sharp peak that reaches almost to the top of the spectrum window. You want to keep the gain as low as possible so that the noise floor isn't raised too high, which can drown out the signal you're trying to decode. Less is more, especially if the transmitter is nearby and you have very strong reception.

Made those changes to the alias, and also did adjusting to the gain.
Same thing still happening

 

[kyscan23]

I was also able to grab these in the "messages" tab

These first 4 are when I was not able to hear a transmission







This one is when I was able to hear a transmission

 

[maus92]

now shows measured error, still no change in proper decoding though

View attachment 142953

You should set the PPM to the value you had previously (-1.009) or just -1.1 as indicated, then uncheck the "Enable decoders to auto adjust PPM"

 

[maus92]

I went down to 165 gain and this is what the signal looked like.
View attachment 142756

While at 165 gain I also got an encrypted call with algorithm unknown showing in the details. I know this site and there is no encryption.
View attachment 142757

I then went to 0 gain and had no improvement either.

I have noticed that if transmission is over 5 seconds then it is decoded correctly.

What are the thoughts of changing the sample rate? Computer resources not powerful enough?

I also do appreciate you all trying to help me out!

What are your computer resources / specs?