BCD436HP: P25 Adjustment Mode Question

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Bolt21

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I travel through Polk County (Florida) which runs a P25 Phase 1 CAI Exclusive system. Work takes me through 20-25 county/city systems on a regular basis, and this one is by far the one that my 436 has the most difficulty with. I run either I-4 or SR60 across the county, so I hit a pretty good sampling of towers/conditions.

I'm no expert, but I believe that I'm encountering both LSM distortion and low signal strength at different locations during my trips. I also carry a P7100 specifically for monitoring Polk County because the 436's performance on this system is so poor. I'd estimate that I'm only hearing 60% of the traffic with the 436. I've tried numerous antennas, attenuation, everything that I can think of - nothing seems to help.

My question is this. Manual P25 threshold adjustment mode of 7 or 8 achieves good results while stationary with good signal strength. Would there be any advantage to using auto versus manual in the varying conditions while mobile? I've used both, and the advantage is not glaringly obvious in favor of one or the other. Just wondering if there is a theoretical reason that one would work better than the other.

And Uniden techs, if you're reading this, fly your family into Orlando, drop them off at Disneyworld, and head west on I-4 across Polk County. This system is certainly a worthy opponent to the 436's decoder. Just make sure you bring a professional grade radio, because the difference is night and day.
 
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SOFA_KING

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I had the exact same experience in Polk, except I didn't have a pro grade rig to see what I was missing. I just knew I wasn't getting hardly anywhere near the traffic I should have been getting. There was another county up north, which I forget if it was Ocala or Gainesville...Gainsville (I think) that had issues with locking onto one of a few control channels. I watched it checking each one, and that caused so much delay that very few voice transmissions were actually received. Leon County the same. My PRO-197 did much better on both of these systems! I didn't look that deep into Polk, but just gave up due to the PITA of the situation.

It would be nice if there were some real technically knowledgeable communications people designing these scanners, but as we observe time and time again, that apparently is not the case. I give them credit for trying, but feel they quit after a certain point. That leaves us frustrated, as we have these unresolved performance issues that leaves us hanging. True, these "boxes" cover a lot of territory, but I wish they put that extra effort into issues like this.

Phil
 

goodmore

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Location seems to be the issue. There is so many variables that these scanners just can't control them all. In my location I was fooling with auto 8 vs manual what ever and just had frustration after frustration. The TRX models worked right out of the box. Another state the exact opposite is reported.
 

Bolt21

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There was another county up north, which I forget if it was Ocala or Gainesville...Gainsville (I think) that had issues with locking onto one of a few control channels.
Yes, Alachua County (Gainesville), is not so great on US301 in regards to locking onto cc's. Marion County, another P25 P1 exclusive, is not much better than Polk in places, specifically near the Belleview exit on I-75 and just about everything north of Ocala on 301. Marion is actually the other main reason for my P7100 use.

Location seems to be the issue. There is so many variables that these scanners just can't control them all.
That's what I'm afraid of. Just hoping that some technical experts here can provide a reason "on paper" that one mode is better than the other in a mobile situation like this.
 

tampatracker

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Hey Bolt I don't usually get into Polk too much but the few times that I have driven SR60 over to Vero I've had pretty good reception on my 436. And also occasionally I will receive Polk County on my 436 from my location in South Tampa. Always at night usually unbroken consistent reception. I do not live in a very high building actually I'm on the ground level, in a wood house so there is no advantage there. I have played around with my p25 settings and I have found that a level of 6 on manual will quite often do the trick. 7 can be even better at times especially with Pinellas, and eight doesn't really do the trick on a consistent reception basis. I hope that helps, t. T.
 

Bolt21

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Thanks, J. I think I've tried 6 before, but I'll give it a longer test session next time I go through Polk.
 

Ghstwolf62

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I think you're going to have to play with it to find what's best for you.

I know I found 7 manual to work on everything everywhere I've gone in two states I've encountered and it works really well at that setting. Others say auto or auto 8 while others turn it way up or way down and it works for them.

I have no idea why 11 works for one guy while 5 works for another. It just seems to be that way for some reason.
 

Bolt21

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I'd still like to know the answer to the question above. Would like to know if auto was designed solely for dialing in the correct setting, or if it is also functional in an adaptive sense, for adjusting to constantly changing variables.
 
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PHILBERT

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The way to determine the optimal setting is to use AUTO close to one tower location and observe the Auto function adjusting itself and displaying its error rate. It will show you the best manual number to use. But you have to have a strong "clean" signal for auto to work correctly. That's why you don't want to use it for every day listening if you can avoid it.

I did this evaluation on all the systems around me and locked in the best setting. It made a huge difference on decoding cleaner signals with longer range. On both my 436 and 536, the best value on the majority of older mixed mode 800 systems is 10, with conventional V/U P25 peaking at 9. New P25 systems coming on-line now favor 6. On the 325P2 and 996P2 all peak values increased by 1. But I have seen some system transmitters vary from the majority. I credit this to transmitter alignment issues. (it happens)

Manual settings do work and help, but in Polk and Achula I think it has more to do with the scanner seeing too many control channels. If I lived there, I would set the location control Lat/Lon precisely for each tower so there was no waste on scanning useless overlap with weaker tower sites. Most of the RR database systems in this state need a lot of optimizing work done on them to make them work correctly. If you take the time to do these things, performance is enhanced greatly. At least the x36 scanners allow you to do these precision settings on each individual system. Other models don't.

Phil
 

sck

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What actually does that threshold mode do? Is it a receive sensitivity setting?
 

ofd8001

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I've posted this question some time back, but got no response. So it may have something to do with propietary information.

Me, I just try a various combination of settings and use what sounds best to my ear.
 

Bolt21

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I've posted this question some time back, but got no response.
Slightly frustrating, isn't it? I mean, if you can't get a question answered here by the man that knows better than anyone else, what other option do you have? Don't really have much faith in calling a customer service number. Anyways, I wouldn't think that instruction on the proper way to utilize a feature would be proprietary.

I have tried many different settings, but being constantly on the move while in that county, it's hard to know what is the best all around setting because I encounter both signal overlap AND weakness. I just wanted an answer from the manufacturer on which option is theoretically better.
 

Bolt21

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The way to determine the optimal setting is to use AUTO close to one tower location and observe the Auto function adjusting itself and displaying its error rate. It will show you the best manual number to use. But you have to have a strong "clean" signal for auto to work correctly. That's why you don't want to use it for every day listening if you can avoid it.
That's pretty much my theory as well. But moving from one side of the county to the other I encounter so many varying signal conditions, I just had to wonder if Auto was an acceptable alternative.

Further experimentation since my earlier posts has indicated that I pretty much have to tweak the squelch setting all the way through the county. In overlap areas I have to use a squelch setting of 8 or higher, and 2 or lower for weaker areas. Wish there was an auto squelch setting to compensate for these varying conditions.

Thanks for your post.
 
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ofd8001

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Slightly frustrating, isn't it? I mean, if you can't get a question answered here by the man that knows better than anyone else, what other option do you have?
Part of me agrees with that. Then another part says Upman probably has a reason why he can't answer the question, such as in doing so would reveal engineering stuff they don't want the competition to know.

So I just go ahead and make my experimental changes without knowing exactly what is going on, but still getting decent results in the process.
 

SOFA_KING

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What actually does that threshold mode do? Is it a receive sensitivity setting?
No...not sensitivity. It's a modulation peak setting. When you set it manually to the optimal value, it ensures you are lined up correctly and it won't drift off...like it does in AUTO mode.

No secrets and not difficult to get right. I outlined the steps above.

Phil
 

bravo14

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When I visited parts of St. John's county their p25 has problems with signal issues in some areas. For a example at my buddy's place by the airport in the fat back side I don't pick nothing up solid I would get 0-1 bars depends where I sit the radio. I was using the 396 and 436 I used the rs800 antenna and a out side antenna still get crappy signal. Psr 800 did little better. When I go visit again in 6 weeks I'm going to try manual and level 5 see if it does any better.
 
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