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Uniden Advanced Technical Topics For all threads regarding technical performance of specific models or general higher tier, technically oriented discussion of the technology used in Uniden scanners. Please use the Tech Support forum for all normal questions.

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  #121 (permalink)  
Old 01-27-2014, 11:31 AM
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Quote:
Originally Posted by DaveIN View Post
Hi Mike, I would just try the supplied antenna without anything else attached, monitor for a period of time (when the system is active) and see what the audio sounds like. If it works with just the supplied antenna, then it may be time to look at the external antenna system. If it doesn't sound good with just the stock antenna, then it may be time to take it mobile and see if the audio is the same or improves at different locations in relation to your QTH.
Dave,

Let me reference the following post from Max, KA1RBI, including a specific quote:

http://forums.radioreference.com/uni...ml#post2106373

Quote:
The reason for asking is that P25 LSM signals (when simulcast distortion is present) cannot be properly recovered once the signal has been passed through an FM demodulator/discriminator. No matter how smart the firmware is it cannot recover the correct signal if
a) it is processing a signal that's been FM-demodulated, and
b) simulcast distortion is present
So based upon what Max is saying, in the absense of simulcast distortion all current P25 scanners on the market today likely will do a fine job on LSM signals. It's only when simulcast distortion is in play that it makes a difference.

And what I'm suggesting [quite prematurely no doubt] is that the signal is likely still being pulled from the FM discriminator and thus would never truly handle all simulcast systems [in the presence of simulcast distortion] properly.

I was hopeful that Uniden may have been doing something different in that regard, but at this point I don't think so.

Remember, in public safety systems, everyone who transmits/recieves on a simulcast system is not required as part of their regular operating to "find a good spot", "swap out antennas", "null out sites". If properly done, things just work for the most part. And that's because the incoming signal is being "tapped" at the appropriate point in the chain and processed.

If I wasn't lazy, I'd boot up Linux for a day and get all of the necessary stuff in place to run Max's gnuradio blocks to test how it decodes LSM in the presence of horrible simulcast distortion vs the BCD536HP.

Mike
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  #122 (permalink)  
Old 01-27-2014, 11:32 AM
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Hi Mike, got it. Just trying to keep it simple. In depth testing is great, the more the merrier.
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Last edited by DaveIN; 01-27-2014 at 11:35 AM..
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  #123 (permalink)  
Old 01-27-2014, 11:32 AM
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Default Please post the video comparison

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Originally Posted by DaveIN View Post
With exception to the WiFi and display differences, I'd say they are about the same in performance, with exception to a little more RF shielding in the 536 due to the metal case and forward display. I've not noticed any additional noise from the WiFi circuit vs. the 996XT without it.
That would help many decide for themselves

Much thanks

Ben
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  #124 (permalink)  
Old 01-27-2014, 11:33 AM
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Pretty sure berns was specifically talking about simulcast decode.

In any case, these most recent reports are disheartening and my credit card has been slipped back into the wallet...
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  #125 (permalink)  
Old 01-27-2014, 12:06 PM
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Default Real Simulcast Comparison This PM

Need less anecdotal evidence on simulcast performance and more (hear / see) evidence on this topic .

This PM I will go out to the worst simulcast area in Philly (East District) and make another video. I know several guys who live in that area and they have given up on the scanning hobby due to simulcast issues. Even with high gain panel antenna s they were unable to receive anything on their PSR-800's.

Comparison radios again will be with PSR-800 & Uniden 996 plus I will include a PSR 500 to boot - will use the stock and hi gain 800 mhz mag mount antenna's . Stay tuned -
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Old 01-27-2014, 12:10 PM
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From what I've seen (or not) so far, I plan to run Pro96Com off of my PSR500 and compare what I hear to what I see.
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Old 01-27-2014, 12:28 PM
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Quote:
Originally Posted by bberns22 View Post
Need less anecdotal evidence on simulcast performance and more (hear / see) evidence on this topic .

This PM I will go out to the worst simulcast area in Philly (East District) and make another video. I know several guys who live in that area and they have given up on the scanning hobby due to simulcast issues. Even with high gain panel antenna s they were unable to receive anything on their PSR-800's.

Comparison radios again will be with PSR-800 & Uniden 996 plus I will include a PSR 500 to boot - will use the stock and hi gain 800 mhz mag mount antenna's . Stay tuned -
Ben, for what it's worth, in that area of the city, you're better off with a 3" quarter-wave rubber-duck like the Larsen from Tessco. The 24th. District is covered by three different sites, all very strong in that area, if you run any sort of gain antenna, you're always going to have issues. I've been suggesting that to Dick, W3BMA for several years now. The PSR and Radio Shack scanners generally get wasted there too without the ATT on.

Good luck and it will be interesting to see your results; take along a standard paper clip as a third antenna option for that area.
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  #128 (permalink)  
Old 01-27-2014, 12:49 PM
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I think some people are missing some key issues in this thread.

If Uniden has indeed fixed simulcast reception, then the entirety of the antenna discussion is simply moot.

That is, a simple rubber duck should work.

No moving of the radio, no finding a null, no swinging a beam around, nothing.

I have commercial gear, and none of these things are ever issues. Ever.

There's also a long-running idea here that simulcast "interference" is to blame, people should stop with that idea because it's demonstrably false. The modulation technique used in P25 simulcast requires the I and Q branches to be used, and not just a tap from the FM discriminator.

So, enough with the antenna discussion - just use the built in antenna or a duck and let's see what we get.
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Old 01-27-2014, 1:36 PM
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Quote:
Originally Posted by W2GLD View Post
Ben, for what it's worth, in that area of the city, you're better off with a 3" quarter-wave rubber-duck like the Larsen from Tessco. The 24th. District is covered by three different sites, all very strong in that area, if you run any sort of gain antenna, you're always going to have issues. I've been suggesting that to Dick, W3BMA for several years now. The PSR and Radio Shack scanners generally get wasted there too without the ATT on.

Good luck and it will be interesting to see your results; take along a standard paper clip as a third antenna option for that area.
I like paperclip Idea as my third comparison antenna .....
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  #130 (permalink)  
Old 01-27-2014, 2:27 PM
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I was able to get my 436 mobile this weekend, and I can speak for performance on the Phoenix RWC Simulcast A & B sites. Overall, simulcast performance of the 436HP is better than the 396XT, but the 436HP still suffers from multipath distortion. As you can see toward the end of the video, at times it struggles in audio decoding.

Some additional background on the video, I was located at about 40th Street and Baseline, Phoenix, in range of 2-4 simulcast A&B towers. Simulcast A & B transmitters are located at the same tower locations. In the video I am located about 3.5 miles from the Airport tower, 6 miles from the downtown tower, 10 miles from 51st and Van Buren tower, and 11.5 miles from 43rd Ave and Indian School tower.
You will notice some of the 436HP audio decoding struggles at 6:08 & 6:47 in the video, but overall better than the 396XT.

Below is the youtube link to the video.

Simulcast Performance BCD396XT vs BCD436HP - YouTube
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  #131 (permalink)  
Old 01-27-2014, 2:44 PM
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With all the mixed reviews here I'm left confused. On a stock antenna I'm receiving my local simulcast with no issues what so ever. So much better than with my PRO-106. I would go as far as to say that my reception is as good as that of system's users.

Luckily I can test that claim. Next time I'm around an XTS3000 on MPSCS (affiliated to Wayne Co Simulcast) I'll bring both my Pro106 and 536 and line all three of them together.

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  #132 (permalink)  
Old 01-27-2014, 2:50 PM
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Default Baltimore County/City MD

I did some mobile testing today with a pair of 536 radios - both tethered to a simple VHF 1/4 wave whip mounted on the vehicle. In Baltimore City, while traveling from dead center in the City to the area just north of the city line, decoding the BALTIMORE CITY PHASE 1 800mhz system was flawless 90-95% of the time..... the remaining 5-10% of the time, reception varied from somewhat garbled to lost. This is a substantial improvement as compared with all GRE radios. The 996XT never worked well on this system.

Reception of the BALTIMORE COUNTY PHASE I 800mhz system, while in the northern part of Baltimore City and while driving through much of the south-central portion of Baltimore County was flawless 50% of the time and AT LEAST very good (or better) 80-85% of the time. The remaining 15-20% of overall reception time was a mix of mild-moderate garbling or lost transmission. This isn't perfect - but truly is FAR better than historical results on my GRE radios (800, 600) or the 996XT. I should note that the County system includes a great number of towers and has always ( for me ) been more of a problem for mobile reception.

While traveling in those areas, reception range and audio quality of adjacent jurisdictions with standard Motorola digital 800 trunked systems was fairly comparable to my 996xt and GRE radios.

Will plan on conducting some Phase II system testing later today.....
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Old 01-27-2014, 2:55 PM
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doctordave,

Thanks for the info on Balt. County/City. Those are the systems I monitor (mostly County ) and appreciate the report.

I'm still not convinced I want to drop $500-$600 unless I get a 95-100% improvement.

I am still on the fence.......
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  #134 (permalink)  
Old 01-27-2014, 3:02 PM
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Well, this is disappointing. Thanks to 'cellphone' for that video, it's very telling.

I do find the variability in the reports to be highly interesting. Early reports were fantastic, but later reports aren't good at all.

I'm going to continue to stress that antennas aren't key here.

In addition, LOCATION should not be a key either. I've had a commercial radio for 18 months now, and it doesn't matter where I am - 100% decode, all the time, every single time. Doesn't matter where I am, I can be inside the boundaries of the simulcast system, or I can be dozens of miles away - 100% decode everywhere, all the time.

All on a rubber duck.

I do wonder if Uniden has 'tweaked' what they had instead of actually fixing it. That would be supremely disappointing.
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  #135 (permalink)  
Old 01-27-2014, 3:08 PM
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Quote:
Originally Posted by sixtytwo View Post
I think some people are missing some key issues in this thread.

If Uniden has indeed fixed simulcast reception, then the entirety of the antenna discussion is simply moot.

That is, a simple rubber duck should work.

No moving of the radio, no finding a null, no swinging a beam around, nothing.

I have commercial gear, and none of these things are ever issues. Ever.

There's also a long-running idea here that simulcast "interference" is to blame, people should stop with that idea because it's demonstrably false. The modulation technique used in P25 simulcast requires the I and Q branches to be used, and not just a tap from the FM discriminator.

So, enough with the antenna discussion - just use the built in antenna or a duck and let's see what we get.
Say what you will about antenna choice, but there is a thing as too much gain and too little gain. It's a delicate balance for each and every system that's installed. That's why in some 800 MHz. cities you will see the 3" stubby on top of the radio and in other's you will see the 7" "Rat tail" installed; and in more rural environments seeking improved reception, they'll likely be using the 800MHz. dipole antenna. Every system is engineering differently. Philadelphia's new system was designed for 1/4 wave antennas across the board, with all city limit towers facing inward towards the city for maximum in-building penetration. Scanners unfortunately do not have the technology inside them to compare RSSI values of each of the simulcast sites; thus the cause for simulcast distortion and decode issues. The stock Uniden antenna is designed to be "unity gain", therefore go in almost all environments and should ward off distortion issues. Then we come along and think bigger is better and add on the Radio Shack 800 MHz. antenna, which adds about 2.5-3db of gain on 800Mhz. Great if you live far away from a tower site or are monitoring a non-simulcast system; but those who add that antenna in a RF congested area are just asking for issues related to simulcast systems. Each of us needs to know our own environments, bigger antennas aren't always better, neither are higher gain setups. Sometimes we're so close to one tower that a paper clip honestly works better. With that said, until scanner manufacturers add in RSSI threshold monitoring, simulcast issues will always be there in some shape of form, regardless of it being Uniden, GRE, Radio Shack, or Whistler. Chances are, if you live in an urban area such as Philadelphia, the stock antenna is going to be your best bet across the board. Now, if you live in the middle of Central Michigan, our system is designed for 3db gain mobile antennas; which the exception of the various simulcast systems in the Southeast region. This mean you'll likely NEED a higher gain antenna to reliably receive the sites in and around you neck of the woods. For those in Southeast Michigan (i.e. Washtenaw, Wayne, Detroit, etc.), you're best bet is the stock antenna when within those county limits; but you'll likely choose to deal with some multi path issues and use the Radio Shack 800MHz. antenna to provide better all-around statewide coverage for the MPSCS system. Again, there has to be some give and take. Okay, off the soap box for today!
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  #136 (permalink)  
Old 01-27-2014, 3:14 PM
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Default Re: Uniden X36 Simulcast Performance Thread

Quote:
Originally Posted by cellphone View Post
I was able to get my 436 mobile this weekend, and I can speak for performance on the Phoenix RWC Simulcast A & B sites. Overall, simulcast performance of the 436HP is better than the 396XT, but the 436HP still suffers from multipath distortion.

Below is the youtube link to the video.

Simulcast Performance BCD396XT vs BCD436HP - YouTube
Awesome job Joe, thanks for putting that up for us. I got busy with family stuff and couldn't meet up with you out there.

I'm noticing a common theme among all the negative reports so far: they are NOT using the stock antenna. Does it work better or worse on the stock antenna, Joe?

Either way the difference between the two scanners is night and day. I'm very relieved to see such a dramatic improvement on that system.

-AZ

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Old 01-27-2014, 3:28 PM
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See some see this as improvement but I see it as the same.

The latest video (thank you BTW) the audio is clear to a point. It sounds like a MOTOTRBO system I monitor through the PC. Still a little garbled. Then it also shows how the audio drops out.

Both are what I experience listing to the Simulcast here in VA with my HP.

I think saying they "tweaked" something is better than saying they "fixed" it since the new unit is still doing what the old ones were.

I also think those using older smaller units are letting the NEWER units cloud their judgement a little. Anything new will sound better than the old.

Just my opinion. Please keep the videos coming, I am still looking for a good reason to spend the money...lol
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  #138 (permalink)  
Old 01-27-2014, 3:34 PM
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In regards to the block of text above - I've used a variety of ducks, mobile and base antennas on my commercial radios. Heck, even tried a VHF duck.

No differences. 100% decode, 100% of the time.

People - it's not the damn antenna, or where you're located.

It's the receiver.
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Old 01-27-2014, 3:39 PM
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Quote:
Originally Posted by sixtytwo View Post
In regards to the block of text above - I've used a variety of ducks, mobile and base antennas on my commercial radios. Heck, even tried a VHF duck.

No differences. 100% decode, 100% of the time.

People - it's not the damn antenna, or where you're located.

It's the receiver.
That's exactly what I think. Different antennas provide different signal levels to the receiver but has nothing to do with location.
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Old 01-27-2014, 3:40 PM
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Smile AWESOME!! P-25 Phase I & II (TDMA) Simulcast Reception!!!

HUGE IMPROVEMENT OVER ANY OTHER SCANNER!!!

We have tested on the following systems.
City of Houston Phase-II TDMA Simulcast - Perfect everytime while stationary, about 95% of the time while driving.

TxWARN P-25 Phase-I Montgomery Co & Houston Simulcast Sites - Perfect everytime while stationary, about 95% of the time while driving.

Both of these tests done with supplied BNC antenna inside a Suburban. When using a 7/800Mhz digital mobile external antenna, it gets even better!!!!

GREAT PRODUCT!!!!! I will not say these scanners are as good as a real radio yet, but HUGE improvements over any GRE or Uniden scanner...
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