Unitrunker w/ BCD396T P25 System

[K3JCT]

Unitrunker 0.1.0.40
Toshiba computer, XP, w/ sound card input
Uniden BCD396T discriminator tap with Op Amp buffer.

Untrunker and Uniscope see nice looking signal on local 800Mhz trunk system (3600 Control Channel) works great. Same with T4Win program.
On a local UHF P25 trunk system (9600 Control Channel) Uniscope sees nice looking signal but Unitrunker will not decode. "No signal".

On the [view][properties] screen:
NAC 000
Call Sign
Modulation CQPSK
Signal Normal
Profile 0.62

Profile will start below 1 and then work its way toward 2 if I leave it on long enough.

The BCD396T display (on hold) will show the System ID, site ID, and TG. Signal level is 2-3 bars.

Read through Unitrunker help and I think I've tried the suggestion for start up.
Any help would be appreciated.

 

[SCPD]

Hello K3JCT;

Please post some snapshots from the UniScope display. I suspect signal problems ... a good image will give us some clues.

Set symbol rate to 4800 and then ... take a snapshot of CQPSK, another of C4FM, and finally one in oscilloscope mode. You may want to repeat the above at different sample rates (eg. 44100 vs. 48000 vs. 96000).

By "snapshot" I mean use the standard Windows [Alt][PrtSc] key combinations to copy the active window. Use [Ctrl][V] to paste the image into Paint or other program that can save the image to a file.

-rick

 

[K3JCT]

Test Uniscope picture

 

[K3JCT]

Test 2 uniscope picture

 

[K3JCT]

Test Complete

 

[SCPD]

Test Complete

To post an image ... click on the "Reply" or "Quote" buttons as you would normally. When composing your reply ... look for the "Manage Attachments" button. A pop-up window will appear with options for uploading modest sized image files (JPEG, GIF, PNG, etc.)

-rick

 

[K3JCT]

Test upload uniscope images

Tnx Rick

John

 

[K3JCT]

Uniscope 96000 uploads

Here are the uniscope 9600 uploads.

 

[SCPD]

Much better!

The C4FM picture tells me the C4FM software PLL can't get a lock. The CQPSK software PLL is actually doing better. I see some fuzz in the oscilloscope image.

I can't tell if that's just how the signal is coming through (weak, fade) or if some improvement could be done with your set-up. It's very common for a discriminator tap set-up to perform very well on squarish waveforms like Motorola and EDACS - but not so good for more linear waveforms.

As an experiment - you may want to put a small unity gain buffer amp between radio and computer.

-rick

 

[K3JCT]

I have an Op-Amp (LM324) buffer amp between the 396T and the computer. I have experimented with different gain settings on the computer sound card and can get anywhere from no signal up to a "compressed" squarewave on uniscope. I was thinking of driving closer to the system to see if an improvement in the S/N would help, but I am getting two bars on the 396T and it follows the trunk system. I do have a PRO-96 with PRO96Com running and both work OK. I was trying to use one radio for 3600 / 9600 decoding.

 

[SCPD]

Are you using all four op-amps in the '324? Is there any filtering? One op-amp wired as a voltage follower should do it.

 

[K3JCT]

I am using just one section. I set the gain at about 1.5 to get optimum drive on Uniscope.
I built three other buffer amp circuits, two op-amp and one simple transistor. I have tried dc buffer amps and ac buffer amps (with 10uF coupling caps) and also directly from the scanner to the pc sound card. I've also tapped my R/S Pro2005 as a test but same results.
I am curious to see if I increase the S/N what effect that has. Probably have a chance this weekend to drive closer to the system.

 

[K3JCT]

OK, got a chance to ride within a stones throw of the UHF P25 system (9600CC) with my BCD396T, buffer amp, and computer. Unitrunker will not decode the system. Uniscope shows about the same as whats posted above. The 396T had all 5 signal bars lit and would decode the sysID, siteID, and TG info. I tried different sample rates and levels on the sound card.
Just as a test I tuned into the 800Mhz 3600 CC system, which was noisy, and Unitrunker locked right on to it, showing the CC activity.