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improving 500s digital

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ScanTheFreqs

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#1
hello, i am amazed with how much better the digital sound quality on the psr500 is compared with the bcd396ts, however, i have a feeling that my psr500's quality could be a little bit better, and im sure it has do with all of those extended settings. what makes me think this is i have all 5 signal bars constantly, but i miss the beginning of some transmissions, and alot of transmissions kinda "break up" while listening, all while maintaining all 5 signal strenth bars. does anyone have any suggestions, any tweeks i could try making to all those settings to try to get an improvement?? i was gonna mess around with them but i dont feel comfortable working on something i know NOTHING about, there is a google documents spreadsheet explaing all of the expert settings, but again, i dont understand what most of that stuff means,

so any suggestions?? any ideas where i should start? (ive already tried messing with the squelch)
 
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#2
I am noticing an issue as well... I have a full signal reading however some of the audio is cutting in and out (as though it had a weak signal). This is not just on portable units, it is on the dispatch as well...

Any thoughts?

Joe KB9TFH
 
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#3
I also am having the same problem with the signal cutting in and out on both dispatch and mobile unit's also. I tried GRE'S 800 mhz antenna to see if that would make a difference but it did not. I have a uniden 996T and I don't have that problem with it, and I am using the indoor antenna that came with the uniden so I know that it is not a issue with not having an outdoor antenna. I'll probably will email GRE to see if they might have a solution to the issue. If I get an answer to the problem, I will be sure to post it.
 

rdale

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#4
Gotta tell us what system you are monitoring (link to database) if you want help...
 

rdale

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Simulcast digital cannot be well received by portable scanners. Your best bet is a directional antenna pointed at the closest tower to you.
 
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#7
I concur with Rob. Simulcast sites are poorly received on any scanner.
And from what I hear from other hobbyists and my own personal experience with the 500 and the Uniden 396. I have tried everything and every expert setting asnd every variety of antenna. But, if anyone knows the optimum expert settings for digital trunked systems, it owuld be nice to know. In the Chicago area I listen to Midway Airport UHF trunked, Metro Correction Center UHF trunked, and Starcom21 700/800 trunked.
 

ScanTheFreqs

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Statevillian said:
But, if anyone knows the optimum expert settings for digital trunked systems, it owuld be nice to know.
yeah thats kinda what i was aiming for with this whole thread,

although its good to know that its a general problem, and its not just me
 
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#11
rdale said:
Same answer as above... Directional antenna pointed at closest tower.
Actually, not always. See this thread: http://www.radioreference.com/forums/showpost.php?p=796401&postcount=1

The PRWN (Phoenix Regional Wireless Network) is more affectionately known among us Phoenix area scanner hobbyists as the Radio System from Hell (and that's the nice term for it). Most of today's digital lineup does from fair to horrible on this system, even the new PSR radios. So, out of both necessity and frustration, one of the locals here did some experimenting and found that pointing a directional antenna AWAY from the closest site actually yielded better results than pointing it right at the tower.

In short, definitely get a directional antenna but experiment to see what direction to point the thing. You may find that the ideal spot is not at the nearest tower but between two others, or at one a bit farther away. Especially those of you reporting a full 5 bars of signal strength. In the digital world, too much signal can be just as bad as too little.

-AZ
 
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#12
rdale said:
Same answer as above... Directional antenna pointed at closest tower.
The guy clarified and wants to know optimum expert settings. But, I use HH's and I am always on the go. I rely on rubber ducks...no masts, no yagis, no directionals, discones, or coax in my life.
 

rdale

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#13
There are no expert settings that you can change. The only way around a CQPSK simulcast digital system is by using a directional antenna. End of story. Nothing in the scanner can help you.
 
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#15
CQPSK Modulation and the GRE PSR-500/600

I also have a GRE PSR-500 and listen to the ARMER system in Minnesota which has CQPSK modulation. I wonder if any software updates in the future will improve the ability to decode CQPSK modulation, or have we come as far as we are ever going to come with this?
 

rdale

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Software can only do so much. The laws of physics cannot be changed my a line of code :)
 
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rdale said:
Software can only do so much. The laws of physics cannot be changed my a line of code :)
I don't think CQSPK is the full issue. Here's why:

I've got one of the very first old school BC250D's - got it right after they came out. Back then, CQPSK wasn't even in use yet - therefore the only mode this thing was supposed to understand was c4fm. So, when the new PRWN system was being tested out here, I loaded up all the system freq's as a conventional bank and scanned it the way we used to back in the days before trunktrackers came out (now I'm really dating myself, LOL). I was able to decode the comm's just fine on the 250, even though they were using CQPSK, not c4fm. The secret was to simply turn the squelch to nearly full open. Once I did that, it decoded just fine.

Fast forward to today. I experimented a few months back with a "poor man's close call" for the 250 so I could monitor PD when they were nearby. Here's how it worked: I loaded all the input frequencies for the system as conventional channels in the scanner and then had the scanner tethered to my PC. The PC was running a program that would simply tune the scanner 45 MHz higher whenever the scanner stopped on a channel. Brilliant, if I do say so myself. :D Anyway as a byproduct of this experiment I discovered that the BC250D was actually decoding BETTER than my 796D. One of two things kept happening: Either the 796 was being sent back to the control channel too early (whereupon it would realize it was supposed to be monitoring the frequency it was just on and jump back) or it would miss the channel assignment altogether and not decode the comm at all. Meanwhile my old clunky 250 would hardly miss a beat.

Has anyone else experienced this? Could it be that the control channel data is being corrupted because the scanner is having to fight so hard thru the noise of multiple towers and that's why the yagi trick works?

-AZ
 

rdale

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#18
AZScanner said:
Has anyone else experienced this? Could it be that the control channel data is being corrupted because the scanner is having to fight so hard thru the noise of multiple towers and that's why the yagi trick works?

-AZ
Nice work... However I'd doubt that theory - since the scanner isn't on the control channel anymore when it sets up on a voice conversation. You might be on to something though.
 
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#19
rdale said:
Nice work... However I'd doubt that theory - since the scanner isn't on the control channel anymore when it sets up on a voice conversation. You might be on to something though.
I think so too. I'm thinking that the 796 (and other 9600 capable trunktrackers as well) is mistaking something in the voice data for "transmission's over, return to the control channel". That would explain why the BC250 in conventional mode keeps right on decoding while the 796 and my Pro-96 (back when it worked) would stutter and drop out. That, along with garbage in the control channel data as well (thus preventing the hop to a voice channel at all) could be the culprit behind most if not all the issues folks are having on these systems.

Both issues can be addressed with Unitrunker and a two scanner set up. I've got my trusty BC250 for the voice part, and an old BC895 for the data - I guess it's time to spend some time getting Unitrunker going on the PC at home. I also think it's time for manufacturers to consider building a scanner with two receivers, one for data and one for voice. Make it a dedicated P25 only model so it could be tweaked and fine tuned for digital reception without having to meet in the middle somewhere to accomodate listening to analog frequencies.

Taking the thread back on topic now, our local user here in Phoenix has confirmed that a directional antenna GREATLY improved his reception of our local digital system on his shiny new GRE. Head over to the AZ forum for more info.

-AZ
 
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#20
AZScanner said:
Taking the thread back on topic now, our local user here in Phoenix has confirmed that a directional antenna GREATLY improved his reception of our local digital system on his shiny new GRE. Head over to the AZ forum for more info.
That would make sense for a simulcast system like PRWN. Using a directional antenna pointed at one tower (EDIT: well, pointed almost at one tower, but away from the other, offending towers), he's eliminated (or significantly reduced) the "interference" from the undesired towers.

Simulcast is like multipath on steroids. Instead of multipath's several reflected (and therefore drastically attenuated) signals, you have multiple non-reflected, non-attenuated (except by distance) signals - all carrying the same data on the same frequency, but out-of-phase based on receiver distance from the various transmitters (and delays in transmitting among the transmitters, etc.). I imagine that the desired signal/data could be filtered or reconstructed, either electronically or algorithmically (e.g. in a DSP), but I doubt that many, if any at all, $500 consumer-grade scanners do such a thing.

I sometimes explain multipath and simulcast like noise-cancelling headphones... A single tower with no multipath is like no noise cancellation. A single tower with a bit of multipath is like minimal or faulty noise cancellation (you might hear a weird echo of or slightly muted noise, but you can still hear the noise pretty well). A simulcast system would be, worst case, like fully-functional noise cancellation - two identical, strong signals 180 degrees out of phase: you hear nothing.
 
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