Can't top 67% P25 decode rate with Unitrunker

[AggieCon]

I'm fairly comfortable with Unitrunker and DSD+, and I've used the programs successfully for a number of systems. However, I can't achieve greater than a 67% decode rate for one of the local P25 Systems (https://www.radioreference.com/apps/db/?sid=8227). The system is a 5 or 6 tower simulcast system, which makes things fun. It is mixed Phase 1 and Phase 2.

Though the decode rate is marginal, UniTrunker seems to catch all of the calls (there is an EDACS system with mostly the same traffic, so I have a great reference). Unfortunately, the voice decoding in DSD+ isn't good, hence why I'm trying to figure out what I might be able to do to achieve better signal/decode.

Today, I drove to the central tower site, and -- even right below the tower -- I could not achieve greater than 67% decode. The DSD+ voice decode was pretty good near the tower but nowhere near perfect. Is simulcast multipath really that sensitive?

By the way, my WS1080 does great with this system. The "T" indicator is almost always solid, and the voice decode is great. The Phase 2 traffic is amazing in clarity -- even better than the phase 1 (I assume this has to do with the user radios generally being newer and better). (Most of the traffic is Phase 1, I realize DSD+ and Unitrunker don't handle Phase 2).

I've tried a number of antennas, including:
- RTL antenna mount with no antenna
- The short black and telescoping RTL stock antennas
- Paper clip
- Touching the antenna mount stub with no antenna (my body seems to be a good antenna)
- Yagi 800-900MHz (http://www.amazon.com/gp/product/B00L3ZRF9A)
- TV antenna
- TV antenna with preamp
- Stock WS1080 antenna
- ~ 850MHZ whip antenna

I've also played around with the various gain settings.

In SDR#, the control channel is strong, topping 0dB with a noise floor between -25 and -30.

I've read dozens of threads and webpages regarding decoding, simulcast problems, etc., so I'm not looking for you to repeat the basics. I'm wondering if there is something specific about this system that's preventing me from getting a better decode, perhaps relating to the Phase 2 capacity. Also, if anyone has any experience with this system, it would be awesome to compare notes. I'd hate to give up on this, because the audio quality is amazing on my portable scanner.

Here's an example of the decode log file: https://dl.dropboxusercontent.com/u/14976381/P25 Signal Decode Log Sample.txt . It seems to jump between 65% and 68%. There are no error "e" lines.

 

[SCPD]

*giggle*

You're actually getting 100%.

Some systems like this one are less efficient in how they stuff messages over the control channel. Ideally, most systems should sustain 40 messages per second. The system you monitor tops out at 27 messages per second.

 

[AggieCon]

Getting 100%

Thanks! That makes sense. All the calls were showing up, and the log wasn't showing errors.

Now just to work on the voice decode. I've read a lot of your information regarding multipath in the simulcast systems. Any new strategies to get a good voice decode on the computer? My portable does great on this system.

 

[br0adband]

As for Unitrunker and P25 Phase II, it can decode those control channels just fine, it just can't do much else so while you won't be able to monitor the actual audio comms you can still watch what's going on with such a system. Still hoping that DSD+ adds P25 Phase II decode capability in the future, if it does that'll be a major thing in this hobby, seriously.

 

[makingbabies]

I know this is seriously dated, but did you ever have any luck Aggie?

I am in the same boat at the moment.

I've had mixed success playing with the audio cable properties, going from 44khz to 96, but I still seem to get sporadic decoding of Phase 1 signals...

 

[BM82557]

I know this is seriously dated, but did you ever have any luck Aggie?

I am in the same boat at the moment.

I've had mixed success playing with the audio cable properties, going from 44khz to 96, but I still seem to get sporadic decoding of Phase 1 signals...

Read this thread - http://forums.radioreference.com/vo...nitrunker-low-health-p25-control-channel.html especially from post # 11 onwards, see post # 15 also

 

[AggieCon]

Well in this specific case, I was already getting perfect decode. It was just a lower message rate and the Unitrunker signal bar did not know the difference between bad decode on a normal system and good decode on a slower system.

What are you using for a receiver?

 

[makingbabies]

Oh ok. I saw the part about the voice decode not being perfect and figured we were having the same issue.

I am using an RTL-SDR for the control, and it's connected to a large copper 2m J-Pole and the signals are very strong.

But before I ask any more questions, I need to follow the calibration tutorial that BM posted above.