<==> Sync Loss - Bits Processed 1570

[Jon Kreski]

Here are my print screens.  The first one shows the Tuners screen when nothing is playing.  Note the frequency.  This is the desired frequency.  Note that it is the same frequency as in the second print screen.  However, once the first tuner is playing, see the third print screen.  It is getting a different frequency from somewhere.  Not sure how to keep it as the non=playing frequency.  I think this is probably most of the problem or at the very least something that needs to be fixed.  Ideas?

[charley....@gmail.com]

Screenshots won't open for me - they don't seem to actually be attached to the message.

[Jon Kreski]

Hmmm...  let me try them as attachments...  sorry for the inconvenience!

[Ben Saladino]

Have tried increasing the gain?  Have you tried switching from LSM to C4FM? 

[Jon Kreski]

You missed my question about how to tune the frequency that is off on one screen but not on the other.  I had three attachments showing that.  Gain and mode wouldn't do much if I'm not tuned to the correct frequency.  Thanks...

[Ben Saladino]

Yeah, I guess I don't understand your question. If you trying to monitor a trunk system, then the tuners should tune to other frequencies.  The frequency display on the tuners screen is the center frequency of the tuner at the moment, if I'm correct. 

[Jon Kreski]

The question is simple.  When I click on the Now Playing tab I see one frequency.  When I click on the Tuners frequency I see another frequency.  How do I get them to be
the same correct frequency?  I think that is why I get the error message in the subject line.

[Ben Saladino]

Others might be able to help you if you provide more information.  What system are you trying to monitor? Its likely that you don't have a good enough signal or maybe do not have active control channel programmed in, assuming it's a P25 trunked system.  Again, assuming you're trying to hear a trunked system, the control channel frequency will be on one frequency. It can alternate between 4 frequencies typically on a Motorola P25 system, or all of the frequencies on an Harris P25 system.  In either case, voice traffic is assigned to the other frequencies in the system. The tuner can tune to more than one frequency at a time, so it displays the center frequency that it is tuned to. It is not necessarily going to be the same frequency all of the time. I wouldn't worry about trying to make the frequency displayed in the tuner windows match the now playing. You need to worry about making sure you have the correct frequencies programmed in the channel window for the system you are trying to monitor. I hope that gets you going in the right direction. Sceenshots of the channel window  might help us to help you.

[Jon Kreski]

The cchannel I am trying to tune is P25 and has two control channels.  A primary and a backup.  Primary is 853.4625c and the backup is:  853.9625c.  You can find these by going to:https://www.radioreference.com/db/sid/100 and doing a search for "Benzie" without the quotes.  I have included a print-screen of my Channel window below.  Thanks!

[John Jones]

jkr, I am down in Shiawassee county (between Flint and Lansing). I have a tower about miles away (to the SE). I suspect you have a weak signal so SDRTrunk is not finding a control channel to lock on to. 

First off do you have all four Benzie CC channels loaded in your channels entry for Benzie? SDRTRUNK will rotate between the CC channels and lock on which ever is handling commands and traffic. Depending on your location you mau or may not be able to receive from both sites. You can always remove the CC's for the site that you are not "hearing" I have C4FM as the modulation. 

The Frequencies in the "tuners" tab will shift around as they tend to tune to the center of the bandwidth of the voice channels. The display on the control entry of the "now playing" screen will however show the actual frequencies of the CC and Voice channels. 

Once you do start receiving some traffic look at each tuner and you can adjust the PPM (up or down) to get the measured error as low as possible. I've had good luck getting the error in the 100hz plus or minus. Make sur eyou have "Enable decoder(s) to auto-adjust PPM" clicked. Also, what are you using for controls for each tuner? I started off with AUTO and then played with the various values while checkinh back an forth to MESSAGES and Channel tabs.

On my channel display (while clicked on CONTROL I show a signal strength of -24.5 with peaks around -19.8. I have found anything lower than -43 db I do not get good receiving results.

How far away are the two Benzie towers from your house? Do you have an LNA to help boost signal? Type of antenna? How High?

Good luck, John.

[John Jones]

I have a tower about 12 miles away (to the SE).

[Jon Kreski]

John, this is a known strong signal.  DSD+ FastLane has been decoding it for years.  It never misses a beat.  Same hardware.

The frequencies for the control channels are in the Channels tab.

PPM on my Tuners tab is listed at 0.  Is that the measured accuracy or do I need to try and adjust that?  Again, DSD+ FastLane has no problem tuning and following this P25 trunked channel.

Than ks!

[John Jones]

Mine has been a good signal in DSD+ Fastlane. I assume you did try the C4FM modulation. What about trying Hetrodyne verses Polyphaser? I continue to have issues with Polyphaser as after a few hurs of running in Polyphaser SDRTrunk seems to lock up and sync-loss bits starts coming back. So I switched back to Hetrodyne. I am running the most current update 6 Alpha 4.

When clicked on your Preferred Tuner in Tuners what mode are you in? I run Linearity with the master slider all the way to the right while watching the both View Spectrum display and also looking at the Channel display. As I moved the Master to the right I could see the power signal level improve.

[charley....@gmail.com]

Can you show your channels tab?  Below is a series of images that will show how a correctly configured instance of SDRT should look like.  The first is the tuners tab.  Note that the tuner is "tuned" to 851.1125.  This is not the control channel for the site, nor is it any of the traffic channels.  It is calculated by SDRT to be more or less the center channel of the SDR for this system.  Note that I have corrected the ppm of the SDR by -1.2 (Airspy Mini) to zero the ppm.  In the center of the spectrum waterfall is the control channel frequency:  851.1375.

On Friday, March 17, 2023 at 4:17:47 PM UTC-4 jkr...@gmail.com wrote:

[charley....@gmail.com]

The next image is the Channels tab where you configure SDRT to receive the system.  I'm working with the Anne Arundel County system, and it is currently running.  In the Source section, you enter the control channel and the alternate control channels for the site you want to monitor.  The Anne Arundel system is a Phase 2 simulcast system, so in the Decoder section, I enabled LSM.  I believe the site that you want to monitor is a multicast site, thus use should enable C4FM.

[charley....@gmail.com]

BTW, I've assumed that you actually created a system for the site you want to monitor.  In the above post image, there are 5 systems listed.  

The next image below shows the Now Playing tab.  Note that at the moment this image was taken, a call has just wrapped up on talk group 8651 and the slot is about to go IDLE.  

The first line shows the currently tuned and locked control channel: 851.1375.  Note that this is different from the center channel frequency shown in the previous images.  The second line show a CALL in progress (actually just ended in this image.)  It is using the first slot (TS:0) of traffic channel 852.6875 and is using TG 8651.  The third line is IDLE, which indicates that the second slot (TS:1) of traffic channel 852.6875 is not longer carrying traffic but will display until TS:0 goes IDLE, then both will drop from the display

[charley....@gmail.com]

Another image of the Tuners tab after the program has been running for a while and the system used other, higher frequency traffic channels.  Note that the center frequency calculated by SDRT has shifted up to 853.3625.

[Jon Kreski]

OHHH!  Progress!  I changed to C4FM and I added the second control frequency and all the other non-control frequencies to the Source section of the Channels tab.  Three print screens are attached.  The Sync Loss error messages are largely gone and I am seeing events.  However on calls I am only getting a briefest second of audio and only on some of them.  I see the measured PPM error rate has jumped.  Thanks for your print screens!  What are my next steps?  I also see that the Gain section of the Tuners tab is different on mine.  I have the most current version of the software I believe.

[John Jones]

Jon, good deal. Yesterday after I sent my afternoon response I was starting to do some cut-n-pastes. Charley beat me to it and did a nice job helping you out. The gain section appears to be dependent on the type of tuner as I have played with Air-spy mini's, RTL-SDR, Nooelec and SDRplay. Each type has a different set of settings for each model.

Also, you only need the CC frequencies for your site in your Channels tab in the playlist editor. The CC software processing tells SDRTrunk which voice frequency to tune to.  

 In the Tuners tab try setting Mixer/LNA Master setting to auto (scroll all the way to the top setting). See if that helps signal processing. That has worked best for me. Are you still getting any sync loss messages?

As both I and Charley both mentioned I'd bet the C4FM is the correct choice for the Michigan system. That's what I have always used as I have pointed my 800mhz beam to the Ingham, Saginaw, and Genesee county sites. This may change once Michigan goes fully to Phase II P-25.

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[Jon Kreski]

Thanks both for sticking with me!  I made the adjustments - eliminated the non-control frequencies and adjusted the gain to automatic.  It now is decoding and playing audio as expected!  This has cleared up a lot for me.  Thanks again!