Palmetto Project 25 System Reception Issues.

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rdubeii

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Anyone else being driven insane by multipath issues on Simulcast sections of the PAL P25 system? Specifically the Charleston Co. simulcast. I've got both Uniden and GRE digital scanners, tried yaggi antennas to isolate which tower I'm receiving, attenuators, indoor antennas, no antenna, and probably about 15 other things to minimize the problem, but I'm still getting digitization of otherwise strong clear signals. What drives me completely nuts I had a friend bring a Motorola handheld that's programmed up on the system (legally...he works for an authorized agency) and it picks up the system and provides audio clear as day, no distortion at all, while sitting right next to my garbled scanner. I'm definitely not new to radio communications and scanning, but I have only recently started my journey into P25. I guess this long rambing post is all leading up to this half statement/half question: I'm assuing the PAL Proj25 system uses the CQPSK modulation scheme (at least on the simulcast towers), and my scanner is working on C4FM, which mostly works, but not very well. Is there a scanner on the market, or an upgrade for a scanner that will give it the ability to deal with simulcast P25 trunked systems any better than what I've already got?
 

LarrySC

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Since you did not mention what scanners you have I will answer in the blind. The PRO-106 has been reported better than the 96. The updated BC996xt should be better than the older 996's. There is $3000 difference between the Motorola and a Digital scanner. Thats why it works. I live 10 miles from the North tower for Anderson Co and cannot hear it at all. I've done the same antenna things which includes a stacked [2 Headed] Viper on a rotor. I can move about 2 miles toward Anderson and copy OK. The older PAL800 for Anderson used one tower and a lot more power. If I could monitor it full time I could figure out all the extra settings for P25 in the scanner. I have almost 40 customers in Anderson using PRO-106's but not one of them knows how to program. I'm exactly 50 miles from Abbeville and Greenwood Co's and hear them OK on UHF. Thats the idea. P25 low power - multi tower = short range. Good Luck. Larry
 

rdubeii

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Guess I should have been more specific, I've got a uniden BCD996XT and a GRE PSR-600, both have the latest firmware. I've had some limited success pointing a yaggi at the only non-simulcast tower I could hope to receive, but I'm right on the edge of reasonable reception. Especially considering how sensitive the digital broadcast is to error. Also that tower is far enough away from the more populated areas of Chas. Co. that there frequently seems to be no radios affiliated with that tower, at least not on the talkgroups I want to monitor. Oh well, sounds like I'm not the only one aggravated.
 
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no youre not the only one you can forget it as far as trying to listen to charleston the only spot that i can hear them well is on the south end just below mt pleasant when they were on the old analoge 800 systrm i could hear them all the way to kingstree and as far north as almost to pawleys island and when they were on the old vhf system i could hear them all up here in florence on my base and moblie scanners i think they just should have just upgradesw their old vhf system and stayed on it if you ask me
 

evan

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Location seems to be everything. It's very frustrating, and you will find lots of posts from people reporting similar issues with all scanners when monitoring this system.

I found that my PSR-500 worked moderately well when I lived on the Peninsula, but was worthless on James Island and Folly Beach. I've heard that the PSR-800 has slightly improved decoding ability for this system.

Of course, I could monitor the Mt. Pleasant site, which was not part of the simulcast, and get 100% decode; however, Charleston city was not carried on that site, which eliminated most of what I wanted to monitor.

If you are in an area with good signal but too much multipath issues, I found the less antenna gain, the better.
 

hawkeye10

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I would have to agree that this is a location issue for you vs a scanner issue because I can hear the Fort Jackson P25 crystal clear on my BCD996xt with latest firmware. Of course I live 4 houses away from their fence line so I am very close to the Fort and where ever the antenna is.
 

hamstang

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I'll throw this in. My new BCD396XT with the latest firmware upgrade decodes P25 audio in a heavy multicast area(Charlotte-Mecklenburg/Union Co) much better than my PSR-500 which also has the latest firmware.
 

qball

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It all boils down to CQPSK vs. C4FM, simulcast site overlap, and the receiver's distance from those overlapping sites.

The farther the two overlapping sites are away from the receiver, the greater the likelihood to have decode problems...it's all based on timing and not all about signal stregth. I am 2.5 miles from one site, and 18 from the farthest site my scanner can hear. I have perfect signal strength and can't understand a word that is said on the network. The time that it takes for the signal to reach my scanner from the closest site coupled with the signal that arrives millionths of second later from the farthest site means that all I get is garble (if you did this in analog it wouldn't be near the issue because the human ear is not near as discriminating as the vocoder of a digital radio).

I think the most plausible answer I have heard so far is to REDUCE the amount of signal coming from the farthest sites. Using your attenuator, and a paperclip (or dummy load) as an antenna will probably yield better results than a yagi trying to null a distant site's signal.

Then there is the C4FM vs. CQPSK issue...they are different modulation schemes and the scanners don't do the Motorola proprietary linear simulcast modulation (LSM) also known as CQPSK. The scanners are never going to decode it well because they weren't designed to.

And lastly, almost every trunked site out there is going to run about 100 watts out...whether analog or digital. The loss in the antenna combiners is still going to be about 3db, and 10 or 12db gain antennae are going to be used. The reason there is usually a need for a greater quantity of P25 sites is the issue of timing, timing, timing (see explanantion above).

Oh, one more thing....digital radio is here to stay. If you think analog was better, go back and use that old Motorola analog StarTac that you bought from Bell Atlantic, or even ALLTEL (neither of the carriers really exist anymore), in 1992 and see how it works for you. Better yet, embrace analog and quit reading this post from your iPhone.

Sorry, but what were we talking about?? :)

Q
 
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well the digital thing is all well and good but if its on 800 its just not worth anthing my fire dept was on the pal 800 p 25 and we couldnt even hardly get out at all on moblies or walkies so we went to our own vhf all digital system and can get out just about anywhere within a 100 mile radius of our district on walkies and even further on the mobile radios
 

rescuecomm

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What qball is saying is that when the time comes to move to 6.25 or 7.5 khz channel spacing, analog will be done. Only with digital modes can the audio quality be met for voice. With the never ending demand for more spectrum, it will happen. One of the reasons the Pal 800 has not been fully embraced by Pickens County is the number of sites required to get full coverage all the way up to Highway 11. I think that combining all the VHF county freqs into a digital system like TT71 has is the way to go. But not necessarily P25 considering the cost.

Bob
 

cobra

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Columbia Site

I can hear the Columbia data channel but have never heard any voice comms. Yes, my digital scanners are on search when listening to the site. Can anyone tell me if there is any activity going on, and if so what am I doing wrong?
 

cobra

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Thanks, TT71

Okay, Well that explains it very well...! Thanks
 
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