SD City 700MHz LSM performance testing

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Anderegg

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Getting ready for LSM, coming soon to RCS and SD City public safety...ugh.

So, I have been running my 396XT, 436HP, and TRX-1, on the SD City 70MHz system, seeing how well and how consistently they are able to handle the new P25 Linear Simulcast Modulation.

The 396XT doesn't like it. Looking at over 100 error rate at times within a mile line of site of the Cowles transmitter towers. The current RCS is not the best at the same location, but error rates are 1/3-1/2 that of the newer LSM system. Basically, expect at least 2x the garble and breakup you get on the RSC on the nextgen SD City system.

The 436HP and TRX-1 perform better, much better. Decode is about the same, with the 436HP having a slight edge in not dropping out on a conversation. The TRX-1 seems to have a bit of an issue locking in when scanning, and even the 396XT would many times start decoding while the TRX-1 would scan on. For the most part, if the 396XT would start RX while the TRX-1 didn't, the XT audio would be utterly useless anyway.

On my drive home the other morning, along the 94 from downtown up the 125 to Cowles, performance on my TRX-1 was 100% clear decode with a stubby antenna, save for choppy decode passing the cell towers at 94 and Federal, and the 125/94 junction...these are known trouble spots, so this was not unexpected.

The 996XT's in my news car hate the RCS around my station, near 47th and the 94 freeway. That location is flat and high, and I can practically visually see several RCS transmitter locations line of site, so decode is always degraded. 700Mhz SD City system performance in the same areas is much worse, 2-3x worse in fact. Inside my station, using the rooftop antenna, a yagi pointed at Soledad, 996XT performance is broken and choppy, totally unreliable. When I jack the TRX-1 into the same antenna lead, I get maybe 95% decode. Very slight audio garble, not choppy, just not completely clear. Cannot be sure it is not on the transmitting end of things, but even at low signal strength, the TRX-1 performance acceptably for commercial use, when you need to understand voice traffic.

Please post your experiences with this system and what platform you are using to receive it.

Paul
 

Anderegg

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So, testing an older Whistler WS1098 on the SD City 700 system. MUCH BETTER decode and simple "stop on channel" performance vs the TRX series. I tested a TRX-2 at various locations, various antennas and attenuation levels, DSP and DAC settings, and have come to determine it is unsuitable for use with the SD City 700 system. The WS1098 has about a 90% ability to decode voice intelligibly. The TRX is somewhere in the 25-50% at best range. For most testing, it either would not stop on the talkgroups, or when it did, it sounded like undecoded encrypted garbled mess. The testing with the WS1098 was performed side by side with the TRX-2, same antenna, same time, same talkgroups locked in. I posted a side by side stereo audio demo on YouTube as well. It was very surprising that the new version of the same basic scanner performs so much worse.

Paul
 
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