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SDS100 learnings and questions

landradi00

Member
Joined
Sep 6, 2019
Messages
5
Hi team, long time listener, first time caller,etc.

Based in Seattle and primarily monitoring public safety in the city limits, previously with a Uniden analog trunk tracker. Bought an SDS100 recently to add WSP and hopefully overcome some issues in town. A few notes.

1. The default of 400 ms digital wait time with the SDS100 national database rendered Seattle Police unlistenable -- the first 1/2 second often had a full syllable or 1-2 letters or words, and transmissions typically started with either a single syllable indicating the sector of a dispatch call (e.g. Nora, King, etc.) or with an address for a new call (e.g. "4-3-2-1 Main St, at the Starbucks, an assault") Missing a letter/number or two or even just a syllable was very distracting. Moving Digital Wait Time (as a setting under "site") to 0 ms or 100 ms was much better; however, while at 0 ms I did get one single instance of a channel "locking onto" some kind of horrible static / control signal and never breaking squelch, had to turn it off manually.

2. SDS100 beats the analog scanner when in downtown right next to Columbia Tower (main simulcast; a 75-story tower in a concrete jungle type setting), but isn't perfect. Attenuation may help but doesn't render things perfect here. Even with SDS100 on attenuation, it's not uncommon to miss part of an in-progress SPD analog trunking call. As strong as -40 dBm unattenuated within 1 block of the tower; drops to -80 with ATT.

3. WSP has been quite a disappointment. Actual mobile units tend to sound OK to (sometimes) great, but the dispatchers sounds like drunk monkeys talking into a tinfoil covered vocoder. Is this a digital artifact I can adjust on SDS100? Or are the dispatchers typically not great sounding on this kind of digital system? I also get "ghosting" where some prior voice call tends to show up again very faintly as an eerie preamble to the next call. Is this something in my SDS100 firmware version? I have 1.05.01 / 1.01.05. Any pointers for settings to optimize WSP are welcome. I only have ever gotten WSP on the JIWN, never received anything on the database-indicated dedicated WSP freqs.

Comments or suggestions welcome, hope the notion that clipped first syllables may be due to ill-chosen Digital Waiting Time is helpful.
 

sparklehorse

Member
Premium Subscriber
Joined
May 15, 2003
Messages
1,126
Location
Portland, Oregon
As far as the WSP questions, are you monitoring them on their VHF p25 frequencies? Or on one of the digital trunk systems that they are sometimes patched to? Either way, trying the different SDS filter settings and/or a different antenna may help. Also you might get more WSP help in the Washington forum. You could have a moderator move this thread over there if you don’t get good answers here.
.
 

landradi00

Member
Joined
Sep 6, 2019
Messages
5
I have never previously been able to hear WSP on the RR DB listed VHF freqs.

I'm hearing them on JIWN from the Seattle site.

Strangely, mobile units come through much, much better than dispatch. This feels like it must be a digital artifact, since I can hear a mobile unit perfectly clearly, then dispatch's reply (coming to me over the same digital signal) is muddled and sounds clipped/quantized. Partly this is because dispatch speaks fast and formulaically and I don't yet have my "radio ears" for their lingo, but I've verified several times now where the mobile unit is much more intelligible than dispatch.

Also, a few times I have experienced what sounds to me like "ghost echo" of the mobile unit's call in the background during or just before dispatch's reply.

Both of those things might be explained if what I'm heard on JIWN is "patched" in some glitch-prone way.

But specific to SDS100 I wanted to see if there might be codec or demodulation options I could try that could be the cause of what should be a flawless signal (dispatch, presumably hard line?) sounding worse than a signal that's being reflected back out after RF. (Like maybe mobile is using a codec that SDS decodes better than the dispatch codec?)
 

freqseeker

Member
Premium Subscriber
Joined
Jun 18, 2003
Messages
57
Location
Puget Sound WA.
I have never previously been able to hear WSP on the RR DB listed VHF freqs.

I'm hearing them on JIWN from the Seattle site.
First off I'm not using a SDS 100 yet. I monitor the same systems south of you near the Pierce county line. As for Seattle PD try one of the simulcast sites like the Eastside or King county simulcast. You may be too close to Columbia and be under the umbrella. These are just thoughts that come to mind. I have read here that the SDS is better for digital and may be suffering from overload in your area. I may have missed your question here though.
When monitoring WSP I use the VHF P25 frequencies at my location. Have you tried with this radio? I don't use JIWN but have tried their own trunk system in the database a little hidden in Sentinel. Go to USA, Washington, King, Statewide, County Systems, WA State Patrol.
Try appending using King Simulcast. I can receive Tacoma Simulcast perfectly on a BCD436 and BCD536. That site used to carry South King traffic but hasn't lately, so I only receive Tacoma and Olympia. King Simulcast doesn't work well where I'm at even with outside antenna. This system uses the same talkgroups as the JIWN system.
I hope this helps. Trial and error.

Vince.
 

nessnet

Member
Premium Subscriber
Joined
Jan 22, 2007
Messages
216
Location
Kenmore, WA
First, yes, this should be in the WA discussion.....

Here in western WA, WSP uses:

Conventional

JIWN

700Mhz trunking

On the eastside, I hear traffic on both the 700 and conventional
Mix of both...
 

landradi00

Member
Joined
Sep 6, 2019
Messages
5
OK, I've added the VHF 155 MHz frequencies and seem to be getting the same traffic as I got off JIWN, but with subjectively better audio results. (Still strange that the mobile units sound better than dispatch, but dispatch seems not as garbled.) I have not noticed the "ghost" effect on the VHF 155 MHz.

Realizing this may be veering too regional for this forum -- but you fellow WSP listeners, do you know what the "native" or original RF system is? In other words, the mobile units themselves, are they calling on on the 155 MHz frequencies (which then somehow get linked / rebroadcast over 700 MHz and JIWN)? That may be introducing another coding/decoding step which compounds the digital artifacts.
 
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