Multipath interference and distortion

[chas0039]

A couple years back, I gave a GRE 800 a try and virtually all the trunked channels had what the local experts say was multipath interference. Digital signals would morph into Donald Duck gibberish more often than not. I guess I am just in an area where the GRE had no luck )Minneapolis SW, Minn. Project 25 phase I.

My question is, would any of the Uniden models do a better job? I am looking at the Uniden BCD436HP, the BCD325P2, the BCD996P2, or the BCD396XT. Any help would be appreciated. I hate that years of listening in the past will be gone because of "improved" digital and I really don't want to spend $400 on what turns out to be an analog scanner. I can do that for $70.


Thanks

 

[KevinC]

Difficult question to answer.

For me, the 436 and 536 perform quite well on P25 7/800 simulcast systems (I've tried them on multiple system in Texas, Illinois and Nevada). Others report less than stellar results.

We'll see how others respond and you can decide based on all responses.

 

[ofd8001]

Having family in the Twin Cities, I've done a fair amount of scanning up there.

The 536 I had on the most recent visit seemed to perform quite well, much better than the 396XT or 996XT I used in the past. In places the 396XT/996XT would sound fine, but others had the garble issue.

Here in Louisville we also have a P25 simulcast system. Its the same here - 536 much better than the x96 scanners.

If you get a Uniden scanner, you may have to spend a little time tweaking settings to get the best possible decoding/audio quality.

 

[nr2d]

Multi-path in 1 receiver is going to be seen in the 2nd receiver. Unless you change the location on the antenna you will have the same reflections.

 

[chas0039]

Thanks for the responses. I just found that there is a regional forum here and I have narrowed the choices down to two radios so I am going to ask that question in the Minnesota forum.

 

[INDY72]

The BCD 436/536HP's are so far the better choices on LSM systems due to the type of digital vocoder installed in them, vs the one in every other digital scanner.

 

[chas0039]

The BCD 436/536HP's are so far the better choices on LSM systems due to the type of digital vocoder installed in them, vs the one in every other digital scanner.

Thanks. That seems to be the general wisdom. Unfortunately, my choice, the 436, is now starting to have screen failures so it looks like I have to wait some time yet. Uniden says the problems are resoved, but that would mean they were aware some time ago, which doesn't look good.

 

[mikeshepard]

Really depends on the system. Here in San Diego County, the1080 is terrific at digital decode while my 436 is almost useless.

 

[buddrousa]

I do not remember screen failures in the BCD436HP I have only scene a few post dimming of the BCD536HP I own both but have not had any problems as mine are less than 3 months old. My BCDz36HP's out perform my GRE/RS/WHISTLER scanners. But like I have posted in many other threads all of my scanners have a use and are being used.

 

[troymail]

Unfortunately, my choice, the 436, is now starting to have screen failures so it looks like I have to wait some time yet. Uniden says the problems are resoved, but that would mean they were aware some time ago, which doesn't look good.

Hopefully, you're talking about the dim display/backlighting issues and nothing else.... We really don't need to learn of yet another problem with these things.

Either way - can you point me to the description of the problem you are talking about and where Uniden says the problem(s) are resolved?

 

[Badboy536]

I had Multipath interference I had to move my antenna around my roof used different lengths of coax
Even at one point had to run the attenuator.but I finally got 95% of it out of my receive.it didnt matter what scanner I had hooked up to my antenna the 996xt or the 536, 436 it still would get the multipath interference.it only got better after I did all that to the antenna system.but im very happy now.i run a Comet gp9 commercial tuned for 155 and 470 up about 35 feet.its 9db gain on 155 and 12db on 470.

 

[chas0039]

Hopefully, you're talking about the dim display/backlighting issues and nothing else.... We really don't need to learn of yet another problem with these things.

Either way - can you point me to the description of the problem you are talking about and where Uniden says the problem(s) are resolved?

I am thinking of:

1. Headphone jack, seems to be OK

2. Battery Time issues. Firmware temp fix.

3. Fading display, just showing up. http://forums.radioreference.com/uniden-bug-reports/310664-bcd436hp-backlight-dim.html

Uniden stated this to me in response to asking about problems, but to be fair, I was initially asking about the 536:

"Dear Valued Uniden Customer,

The issues with the headphone jack and display are all taken care of along with the resetting of the clock with a firmware update. You can purchase one now if you would like.

Thank you for choosing Uniden
Samantha
Tech Support"

Of course, the firmware fix for the clock doesn't really fix the defect, it just stops it from being brought to your attention every day. The problem is still there.

 

[Boatanchor]

O.T again.

A couple years back, I gave a GRE 800 a try and virtually all the trunked channels had what the local experts say was multipath interference. Digital signals would morph into Donald Duck gibberish more often than not. I guess I am just in an area where the GRE had no luck )Minneapolis SW, Minn. Project 25 phase I.

My question is, would any of the Uniden models do a better job? I am looking at the Uniden BCD436HP, the BCD325P2, the BCD996P2, or the BCD396XT. Any help would be appreciated. I hate that years of listening in the past will be gone because of "improved" digital and I really don't want to spend $400 on what turns out to be an analog scanner. I can do that for $70.


Thanks

Back on topic again...

No scanner or even a $4000 Motorola radio for that matter, deals with 'slow' Multipath interference well.

Here is a short video that shows the effect of slow multipath interference (or Rayleigh or Ricean fading) on a P25 control channel in the 400Mhz band:

https://www.youtube.com/watch?v=eSywTifsZQE

Fast multipath fading/interference, as seen when a vehicle is moving, can be compensated somewhat by the Forward Error Correction (FEC) within the P25 protocol, but slow, deep fades as depicted on the video, which are often experienced between fixed/stationary transmit and receive locations, are impossible to deal with at the demodulation stage.

About the only thing that can help is diversity antenna & receiver systems.