Monitoring starcom with a gre psr 500

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timmer

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Does anyone out there use a psr 500 or 600 to monitor starcom 21? I'm trying to find out what the best setting/settings are for listening to starcom. I still have a little garble/digital noise on some transmissions, but not near as much as my radio shack pro-96 had. I have tried stationary, roam, and off for the multi-site setting. None seem to make a whole lot of difference, maybe a little bit. I don't understand fully the threshold settings. (low, high) and what they do. If anyone has any knowledge/suggestions I would sure appreciate them. Thanks
 

werinshades

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Does anyone out there use a psr 500 or 600 to monitor starcom 21? I'm trying to find out what the best setting/settings are for listening to starcom. I still have a little garble/digital noise on some transmissions, but not near as much as my radio shack pro-96 had. I have tried stationary, roam, and off for the multi-site setting. None seem to make a whole lot of difference, maybe a little bit. I don't understand fully the threshold settings. (low, high) and what they do. If anyone has any knowledge/suggestions I would sure appreciate them. Thanks
What site are you listening to..Simulcast site by chance?
 

stlouisx50

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I experiance the same thing on the Starcom systems. I am no expert on them but have noticed the stronger the signal the better. If you dont have a full strength the transmissions can get pretty garbled.

FYI in the St. Louis are they are switching frequencies on the starcom for NEXHELL rebanding.
 

RoninJoliet

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Yes, if its a simulcast site your gonna have that problem of good one minute and braaaping the next when the GRE500 is getting many signals at once...I have found here in the Chicago area that the "stock" antenna works best on some towers to cut down the signal....I have programmed in the towers seperately in SLists so as not to mess with the "threshhold" and seems to be somewhat better that way, (my opinion)....I listen to one tower T125-Grundy Co thats not a simulcast and its 98% perfect....Using a outside antenna with 9913 coax lowloss helps my Uniden 396 but still at times i get the "flickering" of the CChannel caused by multi-path...Hopefully the ??new scanners from Uniden in the future will address this problem....396DXT/996DXT.....rumors??....
 

timmer

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Thanks for all your replies. I am still fiddling with this radio trying to figure out the best settings. I am in the Springfield area listening mostly to district 9. For the most part, the transmissions are clear, but I do have an occasional problem with garble/digital noise. Like I said, not near as much problems as I had with the Pro-96. I am listening to cc 867.325 and 866.925 as well as 867.9. I also use the stock antenna that the radio came with. It seems to work ok for this area.
 

N9JIG

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Occasional digital garble is a fact of life even for the system radios. The PSR500/600 have the best digital decoding of the various scanners that work on StarCom21 but when the system itself gets garbled there is not much you can do.

The last time I was in Springfield and listened to StarCom21 on a trooper's radio I noticed occasional digital garble and she said that it was not uncommon. For the most part it sounded fine, but she also said it took a while to get used to the digital voice as opposed to the analog voice.
 

sixtytwo

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For whatever reason (RF design, decoder design, no one knows), the PSR500 - while it's better than any other scanner - can't handle the simulcast towers in the SC21 system all that well.

I do hope GRE is looking into this, but the last thing I heard was that GRE said it would be "difficult" to address it. Unfortunately, "difficult" in the Japanese culture means "impossible."
 

N9JIG

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For whatever reason (RF design, decoder design, no one knows), the PSR500 - while it's better than any other scanner - can't handle the simulcast towers in the SC21 system all that well.

I do hope GRE is looking into this, but the last thing I heard was that GRE said it would be "difficult" to address it. Unfortunately, "difficult" in the Japanese culture means "impossible."
The GRE's aren't alone in this, the Unidens are just as bad, if not actually somewhat worse on simulcast sites. The word I have heard is that Motorola is using a different digital codec on simulcast sites and that when scanners are hearing multiple towers they tend to get garbled due to differences in the arrival times of the signals to the receiver.

I have had good luck with both Uniden and GRE scanners by reducing the antenna resource (attenuators, BOS versus external etc.) so that I only hear a single tower in the simulcast set.

Also remember that the sites around Springfield (the OP's area of concern) aren't even using simulcast, each site there is single-site. The only areas of StarCom21 that use simulcast are the several Chicago area sites, Peoria, Rockford and MetroEast.
 

kb9hgi

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I have the 996T and have some garble my self and notice it more on the ISPERN patch for some reason. Some times I hear a tone on ISPERN and it keys the frequency and hear nothing.
 

sixtytwo

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The GRE's aren't alone in this, the Unidens are just as bad, if not actually somewhat worse on simulcast sites. The word I have heard is that Motorola is using a different digital codec on simulcast sites and that when scanners are hearing multiple towers they tend to get garbled due to differences in the arrival times of the signals to the receiver.
You're referring to ISI - Inter Symbol Interference, and it's exactly that, when the symbols (not bits!) get schmeared all over the place due to the signals arriving at different times. This can happen not only due to simulcast sites but also due to multipath.

When things get bad enough, bits get flipped.

From what very little I've heard on this topic from GRE, I think that they don't have error correction that's as good as, say, Motorola. It doesn't take very many wrong bits to make a narrowband vocoded data stream unintelligible, and the GRE will squelch when it realizes it's about to pump out garbage audio. That means a loss of audio, many times are a really critical time in a transmission.

Frustrating to say the least.
 

N9JIG

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I have the 996T and have some garble my self and notice it more on the ISPERN patch for some reason. Some times I hear a tone on ISPERN and it keys the frequency and hear nothing.
Early on during the StarCom21 startup I noticed that when multiple talkgroups were patched together or patched to conventional freqs (often done on the Tollway Maintenance channels then) they sounded much better on the simulcast sites than non-patched channels. Never quite figured out why, but I suspect it was due to the same ISI reasons 62 mentions above.
 

werinshades

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You're referring to ISI - Inter Symbol Interference, and it's exactly that, when the symbols (not bits!) get schmeared all over the place due to the signals arriving at different times. This can happen not only due to simulcast sites but also due to multipath.

When things get bad enough, bits get flipped.

From what very little I've heard on this topic from GRE, I think that they don't have error correction that's as good as, say, Motorola. It doesn't take very many wrong bits to make a narrowband vocoded data stream unintelligible, and the GRE will squelch when it realizes it's about to pump out garbage audio. That means a loss of audio, many times are a really critical time in a transmission.

Frustrating to say the least.
So would this be "correctable" with the current Digital scanners out there? In other words, would the infamous "firmware upgrade" correct how our scanners receive these sites?
 

N9JIG

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So would this be "correctable" with the current Digital scanners out there? In other words, would the infamous "firmware upgrade" correct how our scanners receive these sites?
Both GRE and Uniden have made updates to digital decoding that improved somewhat the quality of digital decode so it stands to reason that they **could**, whther they will remains to be seen.

One update (to the older Pro96/2096 IIRC) was directly in response to simulcast operations in Michigan so I would suspect that further upgrades are possible.
 

timmer

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Once again, thanks for all the input. All very informative and helpfull. I do know that sometimes I hear the digital noise/garble and I will hear the dispatcher tell a trooper that his signals are unreadable, please repeat, so I know they are having the problem as well, not just my radio. I will keep fiddling with the "roam" and "stat" settings to see if it helps any. I may just set it back to "off". Also, as I've seen other posters report, during times of bad weather and heavy cloud cover, there seems to be more problems than other times.
 

sixtytwo

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So would this be "correctable" with the current Digital scanners out there? In other words, would the infamous "firmware upgrade" correct how our scanners receive these sites?
Without knowing the internal design of the radio, it's hard to say - but I will say that it's clear that they have DSP firmware loads completely separate from the CPU loads, so if I were in a gambling mood, I'd say yes.

DSP = Digital Signal Processor, they use this to, um, process the digital signal! More specifically, DSPs are generally chips that are designed to run transformations on inputs and produce the desired output. In GRE's case, DSPs would likely do both the error correction/detection and the decoding of the vocoded voice. In older times, DSPs were hard to upgrade with firmware, it's nice to see that GRE made it upgradeable independently of the CPU (which will handle things like the display, keypad, data storage, etc).
 

werinshades

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It would be nice to see something be done in reference to Starcom. I do know that the users do complain at times, but nowhere near as often as we hear the problems. Those of us in Simulcast areas do have the most issues, but i'm hoping there is a future upgrade in the works that will correct this. This may be the first "pay if you want it" upgrade?
 
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