Unitrunker not decoding

[Phil_KD0SCJ]

I recently received a SDR, RTL2832U & R820T. Setup went fine, and I have it on a 3 band antenna. I am getting very good reception on 150, 450, and 800 MHz. However, I have discovered that many of my public service groups have recently changed to P-25.

So, over the last few days, I have been reading here, and all the resources I could find on the internet. I am now stuck and looking for help.

I have located what I believe to be the correct frequency, per the site frequency database:

SDR# shows a nice signal here, I accidently had the correction turned off during this screenshot, it is actually on the peak:

In fact, it is the strongest constant signal in the 850-860MHz range. The audio sounds very digital, much like a diesel engine idling with some periodic digital hash.

So, it seemed to me like the next step is to get it working in Unitrunker. I downloaded the most recent one, v1.0.28.4, and followed the tutorial at RTL-SDR Tutorial: Following Trunked Radio with Unitrunker - rtl-sdr.com.

I clearly understand that, with this set-up, I will need another SDR. If I can get past this step, I'll order one.

But, it seems to me like I should be able to use my one SDR to see the control frequency and get something to decode. But, it doesn't recognize anything. I hear the exact same digital sounding hash when the 'receiver' is running in Unitrunker (with SDR# off, of course), so I am confident good signal is getting to Unitrunker. According to the tutorial, I should be getting a site window popping up. Nothing.
I have had it running as best as I can configure it for over an hour, and just nothing. I have logging turned on and it creates a file but it is empty. (I turned on the logging option after taking the following screenshot, BTW).

Here is a screenshot of my Unitrunker receiver page, updated after Frazpo's post, 8:07am central:

If I can get past this, then my next question is a general question about DSD+ and VB cable. A few days ago, I charged through this entire process in a less methodical way and installed DSD+ and VB cable. Now, it looks to me like I have to change the default sound devices to support this. If I am using this PC for other purposes (I am, for example, piping audio from a Kenwood R-1000 through it) am I going to have to change these sound device settings every time, or does the DSD+ VB cable method coexist well with other PC applications?

I sincerely appreciate any comments on this. I have about 12 hours of time into the trunking part so far, mostly chasing the wrong frequency, but I think I have that now. I have read everything the forum search and google could offer me.

Thank You!

~Phil

 

[frazpo]

Just a couple observations I have. Your PPM correction is still a little off. Center it with the waterfall of the control channel. Also I can not tell what you have under your audio settings but make sure "Filtered Audio" is unchecked.

Under "Control" check "p25"
Check "Mute" and uncheck "Deemphasis"

Im currently decoding with those settings.

 

[Phil_KD0SCJ]

Thanks for the reply. For some reason, I had correction off during that screenshot. It's right on, actually. (I spent a lot of time assembling that picture, how did I miss that?).

I matched up to your settings.... makes sense, but still nothing, still empty log file. (I tried it with logging off too, just to try it).

I have updating my original post with new settings.

 

[frazpo]

There are times I like to start fresh. If I were you and if you haven't done it already I would close all programs and eject the dongle. Install dongle and startup Unitrunker only and see what happens. I have had mine act weird before and this seem to resolve it. Just and idea. You will get it, it has to be something simple.

 

[Phil_KD0SCJ]

Cold boot without dongle, inserted after boot complete. Along the way, I tripped over a comment to turn listen on in Options. I now get the following log:

Log file originally created as .\R00000001\Tuner-20140815.LOG	 Version: Unitrunker 1, 0, 28, 4
Found 0 associated interfaces.
Found R820T tuner
PLL LO 56000000 prescale 4 Quotient 31 SDM 7281 error 196630.
gain 00 45 ED E2
PLL LO 863282500 prescale 1 Quotient 59 SDM 61991 error 13566118.

 

[PhillyPhoto]

You can try using SDR# to receive the signal and patch it through with a virtual audio cable to a signal receiver in UniTrunker and see if it still won't decode the signal.

 

[n9mxq]

On mine, the correction in SDR# won't work in Unitrunker, and needs to be tweaked while the program is running.

It started at 59, and an hour later (as the dongle "warmed up") I lost signal and had to change it to 58, and a little after that to 57.

 

[frazpo]

On mine, the correction in SDR# won't work in Unitrunker, and needs to be tweaked while the program is running.

It started at 59, and an hour later (as the dongle "warmed up") I lost signal and had to change it to 58, and a little after that to 57.

So your saying that the PPM correction you make in SDR# will not apply to Unitrunker. Mine seems to do OK.

 

[joeuser]

The latest version passes the digital & audio differently. I tried it today AFTER I backed up my current working install which was the last version, & it didn't work default. Its something with the analog & digital signals & passing each one through DSD+ & whatever. There are more posts here on this that I suggest WE read to figure out better what exactly is going on.

 

[n9mxq]

So your saying that the PPM correction you make in SDR# will not apply to Unitrunker. Mine seems to do OK.

Yep, it's only off by one or two, but it's different enough to cause no decode.. Once I figured that out it worked like a champ.. Now I just have to get another 820t as it won't work with my e4000 at all..

 

[Phil_KD0SCJ]

And we have a winner! n9mxq got it with tweaking the correction! Changed it from 71 to 73 and I have 100% health (which makes sense, as I have line of sight with the tower).

Thank you everyone!!!!

 

[n9mxq]

Do I win a cookie? hehe.. Glad I could help..

 

[Phil_KD0SCJ]

I don't see where to do it, it would be great if a moderator could add 'Solved' to this thread title... Anyway, time to order that second dongle.

 

[reconrider8]

My dongle runs from 47 cold to 51-52 warmed up

 

[PhillyPhoto]

Do I win a cookie? hehe.. Glad I could help..

You're cookie:

 

[n9mxq]

I don't see where to do it, it would be great if a moderator could add 'Solved' to this thread title... Anyway, time to order that second dongle.

I think if you click the little red triangle on the first post, you can put your request there.

And thanks PhillyPhoto.. Can never go wrong with Chocolate Chip! :lol:

 

[frazpo]

Your correction was off in the initial photos you took according to the waterfall. Glad its working.

 

[Phil_KD0SCJ]

Me too frazpo, thanks for your help!

 

[reconrider8]

and to go along with that if you lose signal again unmute it and change your ppm in the direction your hearing the cc better

 

[Phil_KD0SCJ]

Recorider8, after some use, I see exactly the same warm-up issue you described.

It takes 10 minutes of the radio being enabled to get good health readings on the site. Just being plugged into the USB port does not help, it is a matter of the radio actually running. I can fiddle with the ppm if I am in a hurry, but I usually just start it when I sit down and do something else for a bit.... like read this excellent forum.