Interesting observation TRX-1 and Simulcast LSM systems -scanner LO drift critical

[chris451rr]

I just got another TRX-1 mainly to use with DMR and NXDN, my other older TRX-1 has not been working on P25 LSM just every other kind of LSM DMR and NXDN>
The New TRX-1 (factory refurbished) is trunking and receiving the LSM just fine.
So, I did the following to the old TRX-1.
Reloaded CPU and DSP firmware with the app.
Swapped memory cards to the older TRX-1.
Still does not trunk the LSM so its a hardware issue not a setting issue.
Searched for the local oscillator so I could compare reference frequency and offsets.
Using a signal generator and the on the air control channel for Cedar Rapids, I did some narrow sweeps to find the local oscillator.
For example tune the scanner to sweep from 775 to 775.2 and observer the LO steps every 75khz between
394.2 394.275 394.35. It can also be seen at 2x and 3x of that frequency.
Next step was to set both the 'good scanner' and the 'bad scanner' to the same frequency so the LO can be compared.
Using a signal generator on the older TRX-1 in the 800 band it was 2khz low. The new Trx1 was not having trouble with LSM but the older
one was. My observation is that signals appear 2khz low on the older TRX-1. The LO is 2khz too high in the 800 bands.
Local oscillator frequency is critical in LSM systems.
Local ocillator reference drifted higher to the point where it will no longer trunk LSM but still trunks any of the other modes ; regular P25 and DMR/NXDN on any band.

My proposed fix is to re-calibrate the oscillator in the older TRX-1 so it is 2khz higher, then give it a try on the LSM system.
The new TRX-1 is trunking LSM just fine in P25-LSM mode. The old one is failing to show the T symbol in the display when the good one does,
but the signal bars are the same.

Conclusion if your TRX-1 used to trunk LSM but does no more particularly on 850mhz band, it has probably drifted off frequency enough to keep it from decoding the LSM types of trunk signal. Both scanners still exhibit the signal chop found in LSM systems but typically adjusting the position of the scanner will fix that(can be weather dependent)
Waiting to hear back from Whistler to see if they will tell me how to adjust this or if they want me to send it back.
They provide no technical information on this scanner at this point.
Chris 8/3/2019

 

[Anderegg]

I bought a new TRX2 that simply cannot, under any set of settings or antenna placement, decode the local 700MHz LSM, where my fleet of WS1098's has absolutely no issues on the same system. I asked Whistler if they could send me a test loaner TRX2, because I bought the TRX2 to evaluate the model for a full phase II scanner upgrade at my TV station...over 20 scanners. They told me they don't do "loaners", not even if I left a deposit. Nice to see someone found an issue with the new TRX's.

 

[chris451rr]

I bought a new TRX2 that simply cannot, under any set of settings or antenna placement, decode the local 700MHz LSM, where my fleet of WS1098's has absolutely no issues on the same system. I asked Whistler if they could send me a test loaner TRX2, because I bought the TRX2 to evaluate the model for a full phase II scanner upgrade at my TV station...over 20 scanners. They told me they don't do "loaners", not even if I left a deposit. Nice to see someone found an issue with the new TRX's.

I have confirmed the TRX-1 receiving the trunking and talk channels in the P25 Phase 2 system nearby.
Making some huge recordings of the control channel. There are talk groups and encoded channels that are not listed here.
This is great news for Whistler users.
I also heard back from Whistler scanner support.
If you have updated it to the latest CPU and DSP firmware and it still doesn't work on the P25,
they say it needs service. Maybe a lot of new radios were not aligned correctly for LSM.
Report back here if you got a new radio that did not work on LSM.
The radio can be sent back to them and the charge is $120.

I have made progress understanding the frequency scheme in side the radio,
and I can tell you it will take frequency standards, oscilloscopes, signal generators and test signals
to align it. My older trx-1 did P25 initially and there were no P25-Phase 2 to test it with.
Over a period of time it stopped receiving the simulcast downlinks but did OK with the repeater inputs
and most Phase 1 signals. It did not pickup some VHF phase 2 that is similar to some 700mhz phase 2,
so the alignment appears to have something to do with the discriminator and some D/A converters.
The higher frequency oscillators are still very close on the older and newer TRX-1
It is probably worth while to send it back although I am looking at it some more to understand it
and try an alignment.

There may be a large number of TRX-1 and TRX-2 in the field that need alignment from what I've heard.
One caveat I am locking my working TRX-1 down on one system at a time. Scanning dwell would have to be quite long to get the p25 and P25 phase 2. On simulcast you have to adjust the position of the radio to get the trunking clearly. Honestly I lay the radio horizontal.
Its a lot better than getting no trunking at all on these.
On both radios the 'FSK' type waveforms always have worked perfectly.
The Phase Mod waveforms need a perfect alignment. The phase mod waveforms will decode but there is something in the alignment that has to be perfect.

 

[eyes00only]

Bummer that they charge big bucks to fix a problem that's theirs from the start.

 

[nosoup4u]

This actually makes a lot of sense. My observation on these forums of Whistler/GRE owners over the past years is either people love or hate these radios with a passion. It would seem that not all these scanners have been created equal and Whistler may have some serious quality control issues.

 

[crazyretrotech]

Yep have to agree with this as my 1080 had issues with LSM working till it was on at least for 5 to 10 minutes, likely for oscillator and components to become temperature stable, it did fine on everything else. The new TRX 1 bought used, but mint condition been great and don't need to warm up and it pulls in stuff the SDS100 has issues with to the point need higher rated batteries as drain them in about 6 to 8 hours. Yes the SDS100 is untouchable when it comes to LSM, but analog and even DMR & nxdn prefer the TRX-1 as pulls in stores and tow trucks that the SDS100 can't. Now have the TRX-1 on a outdoor antenna with a active splitter/preamp filter setup and works flawlessly without overloading. Did had to change primary CC and lock out others to get LSM to work good.

All scanner before SDS100 had issues with overloading on LSM is a common issue due to lack of a IQ demodulator circuit, just have to test environment and see what causing the overload strong signal nearby and get filter and lock out CC to get it to work reasonably well. The TRX-1 does have a improved front-end compared to the WS-1080 I use to have.

 

[crazyretrotech]

Now for the original poster if it isn't receiving LSM at all, when other same scanner does, could be a alignment issues as he stated as he did narrow it down. I would call Whistler and see if you can have it repaired as they do at times offer discount if you argue with them a bit

 

[crazyretrotech]

Bummer that they charge big bucks to fix a problem that's theirs from the start.

They do refurbish the whole scanner for that price, so if scanner has wear and beat up, is worth it. If not a phone call and they may come down in price as did get them to repair my ws-1080 for $90 bucks as logic board was shot.

 

[chris451rr]

I have really narrowed down what is going on.
The radio uses a fixed 'pre set' crystal of 12.75 mhz. No trimmer it either works or not.
The FSK waveforms like DMR or narrow like NXDN work because they are square wave or
because they still fit in the bandwidth. The LSM gets chopped off in the bandwidth,
and the DSP sees garbage instead of the phase jump. Apps like Unitrunker
This is divided to 75000. Then this is divided by 50 or 60 to get a 15 or 12.5 step.
The synth only supports 12.5 steps in the 851-940 range.
The cumulative error of two crystals is what causes the problem.
The IF 381.8 to 381.9 mhz seems OK but slightly low. The High LO 471mhz is slightly low.
The two of them start out OK (or maybe not even when new).
They have no adjustment for the 12.75 mhz ref crystal.
The VXO part has a glued lid so I have not looked in there yet.
Most likely they just change the whole RF board since they'd have to desolder an SMD crystal buried in a tin shield.
As these parts age they drift up (so RX drifts down) and a time standard part I've worked on is ordered 6 months ahead of time and aged hot for a long time til it makes the spec.
So you will probably get a new RF board during repair, real easy to swap it out on their end.
.
Ill go see if their HQ has an LSM nearby maybe they use it to test with now.
-Chris

 

[chris451rr]

I bought a new TRX2 that simply cannot, under any set of settings or antenna placement, decode the local 700MHz LSM, where my fleet of WS1098's has absolutely no issues on the same system. I asked Whistler if they could send me a test loaner TRX2, because I bought the TRX2 to evaluate the model for a full phase II scanner upgrade at my TV station...over 20 scanners. They told me they don't do "loaners", not even if I left a deposit. Nice to see someone found an issue with the new TRX's.

If its less than a year old send it back to them and say its too far off frequency to receive LSM.
The LSM QPSK waveform is tall fm spikes and if those get clipped it won't decode.
Most likely it does fine on nxdn and DMR where one is narrow and the other is FSK.

 

[JD21960]

I love that photo of the TRX-1. "Turbo Receive" whatever that means?

 

[Anderegg]

Chris, is this a TRX specific issue, or do you think the older WS's are suceptible as well? My WS1098's are gangbusters on the local LSM systems, assuming the antenna placement at my base location is very specifically located. TRX2 on the same antenna is impossible to not LSM garble no matter what.

And for Whistler, thank you for not sending me a test/loaner TRX2 (We don't fdo loaners) after I informed you it was unable to receive LSM that the WS1098 could, and wished to rule out a problem/defect with the new test TRX2 rig...my station went with $9000 in Uniden gear, so again, thank you. I henceforth flamed the TRX and reccomend not to buy for LSM systems. #shotyourselfinthefinancialfoot

Paul

 

[crazyretrotech]

Chris, is this a TRX specific issue, or do you think the older WS's are suceptible as well? My WS1098's are gangbusters on the local LSM systems, assuming the antenna placement at my base location is very specifically located. TRX2 on the same antenna is impossible to not LSM garble no matter what.

And for Whistler, thank you for not sending me a test/loaner TRX2 (We don't fdo loaners) after I informed you it was unable to receive LSM that the WS1098 could, and wished to rule out a problem/defect with the new test TRX2 rig...my station went with $9000 in Uniden gear, so again, thank you. I henceforth flamed the TRX and reccomend not to buy for LSM systems. #shotyourselfinthefinancialfoot

Paul

For LSM won't recommend anything else pre Uniden sds100/200 as all scanners before sds100/200 don't handle LSM very well due to lack of a IQ demodulator circuit. In some areas like rural areas the Whistlers work great, but in high RF area forget it, you can in some case get the trx-1/2 to work, but you have to lock out CC and help if you use directional antenna maybe test environment and order filter to prevent overloading front end for them to do well in high RF area. The Uniden SDS100/200 can overload on lower bands mainly, but shines on 700/800Mhz LSM systems. Where the TRX-1/2 shines on everything else better. Reason why I have multiple scanners/receivers. The unication pager g4/g5 are also a good choice for LSM, but are not scanners,

 

[Anderegg]

I am actually finding my WS1098 to provide superior 800 performance compared to my SDS200. There is a local distant 800 3600 SmartZone site locally, that the SDS200 cannot receive, because it is getting bleedover of weird pager signals, and even audible off freq voice traffic from different trunking systems. When the interference breaks for a few seconds now and then, the control channel can be heard at -50dBm, but if the CC is knocked off the air, then it cannot receive any traffic. My WS1098's receive this system perfectly fine, full 100% clear decode. I have a yagi, I have the ATT function, nothing I throw at the SDS can clear the interference, not even the various filters. My TRX2 has beter sensativity on 800 3600 systems than my WS1098, but the obvious inability to receive LSM makes that a mute point. My little yagi does more to reduce interference than to amplify target signal...on my SDS200, when the interference strikes, it can be reduced by as much as -10dBm by using the yagi. Unfortunately, the interference already throws a more powerful RSSI than -50dBm!

I am past my 1 year mark on my new TRX2, bought specifically just for testing on LSM. The email I sent to Whistler was in January or February 2018...maybe if they are confirming there is a warrantyable issue, I can get them to warranty mine simply because of the date at which they were notified of the problem.

Paul

For LSM won't recommend anything else pre Uniden sds100/200 as all scanners before sds100/200 don't handle LSM very well due to lack of a IQ demodulator circuit. In some areas like rural areas the Whistlers work great, but in high RF area forget it, you can in some case get the trx-1/2 to work, but you have to lock out CC and help if you use directional antenna maybe test environment and order filter to prevent overloading front end for them to do well in high RF area. The Uniden SDS100/200 can overload on lower bands mainly, but shines on 700/800Mhz LSM systems. Where the TRX-1/2 shines on everything else better. Reason why I have multiple scanners/receivers

 

[crazyretrotech]

I am actually finding my WS1098 to provide superior 800 performance compared to my SDS200. There is a local distant 800 3600 SmartZone site locally, that the SDS200 cannot receive, because it is getting bleedover of weird pager signals, and even audible off freq voice traffic from different trunking systems. When the interference breaks for a few seconds now and then, the control channel can be heard at -50dBm, but if the CC is knocked off the air, then it cannot receive any traffic. My WS1098's receive this system perfectly fine, full 100% clear decode. I have a yagi, I have the ATT function, nothing I throw at the SDS can clear the interference, not even the various filters. My TRX2 has beter sensativity on 800 3600 systems than my WS1098, but the obvious inability to receive LSM makes that a mute point. My little yagi does more to reduce interference than to amplify target signal...on my SDS200, when the interference strikes, it can be reduced by as much as -10dBm by using the yagi. Unfortunately, the interference already throws a more powerful RSSI than -50dBm!

I am past my 1 year mark on my new TRX2, bought specifically just for testing on LSM. The email I sent to Whistler was in January or February 2018...maybe if they are confirming there is a warrantyable issue, I can get them to warranty mine simply because of the date at which they were notified of the problem.

Paul

This is very true it is the TV tuner chip they are using in the sds100/ 200 is what I suspect? The only good thing about the Uniden sds100/200 is does well is with simulcast without distortion. Playing with the filters setting on each site instead of global default "normal" it picks up most traffic pretty much on that system with close to 100 decode rate with -75 to -80 RSSI.

I still prefer my TRX-1 for VHF/UHF, it picks up the stuff the Uniden sds100 can't. TRX-1 listen to utilities, Schools, buses, tow trucks plus Wal-Mart and malls in area and doesn't have bleedover issues that the Uniden does. The sds100/200 forget it, as would miss 90 percent of that traffic, if it even get it at all on same antenna/pre-amp?

 

[crazyretrotech]

Don't bother emailing Whistler, they usually don't respond back. I just would call them directly.

 

[Anderegg]

I just picked up a TRX1 from a coworker so I could update it's programming. My TRX2 test unit has horrible LSM garble, completely unable to receive unlike my WS1098's which receive LSM very well (stationary location). The TRX1 from my coworker on the other hand, receives LSM better than my WS1098's. Go figure.

Paul

 

[Ubbe]

Set both TRX scanners to the same frequency and listen to the local oscillators, that Chris suggests, from a third scanner. If you position the scanners so that you get the signals at about the same strenght you'll hear the beat tone that indicates their difference in frequency. A 1Khz beat tone says that they have a 1KHz difference in frequency. A low frequency tone of 500Hz or lower, that would be hard to hear but set the listening scanner to CTCSS decode that then could decode below the 250Hz range, would indicate just a smaller frequency difference and the theory of bad simulcast decode due to frequency error are then not the correct explanation to the difference in decode quality.

/Ubbe

 

[dvendt]

This actually makes a lot of sense. My observation on these forums of Whistler/GRE owners over the past years is either people love or hate these radios with a passion. It would seem that not all these scanners have been created equal and Whistler may have some serious quality control issues.

That goes for Uniden also. I loved my PRS500 until the batteries peed all over the key pad pcb.

 

[seth21w]

For those with lsm systems try -2 ADC 0 DAC 48 DSP I can beat my sds200 on lsm sometimes. The sds doesn't pick up short replies very well.