TRX-1: Anyone try X2-TDMA? Serious bug here...

[devicelab]

When listening to a local X2-TDMA system the voice channel keeps getting cut off when the scanner shows the CC channel on the display. It's similar to the older days of having Wx Priority turned on.

Dispatcher is talking away and every other second, his audio cuts out. I noticed on the display that it's cutting out exactly when the display is showing the VC and CC frequency. When it's on VC the audio works great but then it shows CC and the audio cuts out... and back and forth until the conversation is done.

It's happening on either side of the convo.

I can post a video link of this later if it would make more sense.

This is the system in question: King County Metro Transit Trunking System, Seattle, Washington - Scanner Frequencies

 

[TAbirdman]

what Firmware/DSP are you running with this issue? If its the latest have you gone back a rev and try it? If its not the latest then update everything and retry it.

 

[AggieCon]

If the rotating advanced display setting is really causing all of the simulcast problems everyone has, I'll eat my hat. On the General Settings tab of EZ Scan, in the bottom left, change the Blink Times to something like 2.5 sec and see if it still does the same. Or even turn the Display Mode to Simple.

Likely, you are just dealing with distortion due to the scanner hardware not legitimately supporting the modulate scheme utilized by Motorola in its Linear Simulcast Modulation (LSM).

Edit: Travel and monitor one of the other two sites and see if it does the same.

 

[scosgt]

Could changing the dwell time help?

 

[scosgt]

And what about system delay?

 

[devicelab]

If the rotating advanced display setting is really causing all of the simulcast problems everyone has, I'll eat my hat. On the General Settings tab of EZ Scan, in the bottom left, change the Blink Times to something like 2.5 sec and see if it still does the same. Or even turn the Display Mode to Simple.

Likely, you are just dealing with distortion due to the scanner hardware not legitimately supporting the modulate scheme utilized by Motorola in its Linear Simulcast Modulation (LSM).

Edit: Travel and monitor one of the other two sites and see if it does the same.

Works fine on the PSR-800 just for reference. Yes, they do use LSM but again, it works great on the PSR-800.

Will try the other settings later tonight.

 

[devicelab]

what Firmware/DSP are you running with this issue? If its the latest have you gone back a rev and try it? If its not the latest then update everything and retry it.

Latest firmware but pretty sure it happened before the NXDN upgrade.

 

[AggieCon]

Very interesting. I missed the note that you were comparing to a PSR-800. Have you read the posts about all the troubles people are having with NXDN voice dropping out or coming in late? Think your problem may be similar?

 

[devicelab]

So here's what I did:

1. Changed from Advanced -> Simple: No effect
2. Changed to 2.50s Blink Times: No effect (seemed worse)
3. Tried different times: No effect (seemed worse)
4. Reverted to 0.75s Blink Times: N/A
5. Deleted 2nd site (just the primary site): No effect
6. Delays are 2.0 on both scanners
7. I didn't mess with Dwell Time. (The PSR-800 doesn't have this option.)

Known Differences:

1. PSR-800 is detecting it as "DG" and the TRX-1 as "D2" -- so I'm curious if that's the problem.
2. PSR-800 has the complete list of TGIDs (no wildcard) whereas the TRX-1 is just scanning wildcard TGID.
3. PSR-800 has rubber duck and TRX-1 has external discone antenna. (I've tried reversing them and there's no difference. It's not a signal strength issue.)

Video Link:

(The PSR-800 volume is low and the TRX-1 volume is high.)

In the last 10 seconds or so, you can clearly see the dispatcher cutting out when the display shows the CC.

https://www.dropbox.com/s/ai23e4wykqq3aw2/KCMT.mp4?raw=1

 

[devicelab]

Have you read the posts about all the troubles people are having with NXDN voice dropping out or coming in late? Think your problem may be similar?

Yes but sadly we don't have much NXDN around here. I'm seem to do fine with NXDN conventional frequencies (and if the signal is good enough.) Trunking has been hit/miss at times but I think that's due to my low signal.

I'm planning to check out some areas with NXDN specifically next week to see if that helps with the trunked NXDN systems.

 

[AggieCon]

Simulcast problems in my humble opinion. You're just correlating it with the CC showing because every time it picks up something, it's going to display either the voice channel or the control channel frequency.

What if you swap the antennas?

 

[AggieCon]

That may come off wrong... I haven't been able to stare at it as long as you. I just have that one video. There could be something to the CC frequency displaying and it cutting out; but from the short view that I have of the situation, it seemed to be normal operation as far as the display is concerned.

 

[devicelab]

Simulcast problems in my humble opinion. You're just correlating it with the CC showing because every time it picks up something, it's going to display either the voice channel or the control channel frequency.

Well duh, that's because the audio is being cut off when it shows the CC on the display. Simulcast problems? In what sense? You're saying the system has problems? That makes no sense. It would have problems on the PSR-800 if that were the case.

What if you swap the antennas?

Makes no difference. Can put both rubber duck antennas and the PSR-800 still performs 1000% better than TRX.

That may come off wrong... I haven't been able to stare at it as long as you. I just have that one video. There could be something to the CC frequency displaying and it cutting out; but from the short view that I have of the situation, it seemed to be normal operation as far as the display is concerned.

Are you listening to the audio? I don't care about the display issue so much. Why is the audio cutting out every couple of seconds??? That's the problem here.

Listen from 0:34 ... why is the TRX cutting out? There's an active conversation going on and the TRX should be picking it up. The dispatcher was talking for several seconds.

 

[INDY72]

Different scanners handle systems in different manners. Your PSR-800 may actually be just perfect for the said system, while the TRX may not work quite right without playing with every conceivable setting known to man, whilst an 436HP may totally crap out on it or vice versa. Simulcast distortion does not affect every scanner the same way. On an Phase 2 LSM you could find just the reverse. I would keep trying to configure the settings in every way possible, and then try different antennas, attenuation etc...

 

[03msc]

That would be frustrating for sure. Does seem to be acting like a simulcast issue but the PSR-800 working fine does leave one scratching their head. You do know what AggieCon meant when he said simulcast problems, right? He isn't saying it's a problem with the system...

Something is causing it to drop the VC and then it checks the CC for traffic (as the display shows) and then goes back to the VC for more traffic; it drops the VC again and repeats the process because it knows traffic is on the system. I'm not sure what the display shows but the WS1098 in my mobile will sound like that when receiving traffic and I get near a cell phone tower (overload/desense). I wonder if the TRX is just more sensitive to something like that than the 800? Have you tried turning on the ATT on the TRX and see if that makes a difference?

I know I'm not really helping much...just thinking out loud...

 

[devicelab]

Different scanners handle systems in different manners.

The PSR-800 and TRX-1 should have relatively the same firmware since they're made by the same engineers.

For the record, the 436HP and 996P2 work just fine with this X2-TDMA system.

 

[AggieCon]

The PSR-800 is no longer supported by any entity, I believe. The firmware for the TRX-1 is ahead of the PSR-800 by quite a bit, version wise (note that I'm not saying that the firmware versions are actually better in every way, just that they are newer).

Additionally, there are some very minute hardware differences in the two scanners. Perhaps that is coming into play.

I listened to the audio and watched the video. I believe the problem you are having is due to the scanner not having true support of P25 LSM (simulcast modulation). I am not sure if any other topic--besides encryption--has been discussed to such length on this forum as simulcast reception problems.

On the bright side, lucky for you that you have a scanner that receives your local simulcast system well. Awesome! A lot of people are left high and dry. And now you have a spare scanner for exploring NXDN and DMR. Merry Christmas!