BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment

[sprite1741]

I just got my new 436 running Friday so I am out of the loop here. I have excessive hiss and some signal loss at 460.100 Mhz that I don't notice on my other scanner. Is that what the tape is supposed to help?

 

[k3fs]

Yes. It will improve reception of UHF and to a lesser degree VHF.

 

[bearcat]

Just to add another data point, I applied 2 layers of this foil tape to the inside of my battery door today:

https://www.amazon.com/gp/product/B00DY9IXFI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Then I monitored a busy fire ops channel on 453 MHz and saw no detectable difference with the foiled door vs without it. This ops channel is analog, about 30 miles distant, and with the RS800 duck I was averaging 2 to 3 bars. There is a fair noise floor on this signal as one might expect on a duck antenna, and the signal to noise ratio did not audibly change when removing the foiled door. I put both layers of foil tape over the foam pad, however with the first one I left a small section of the paper backer material in place so that the tape would not stick to the foam pad.

Perhaps this isn't the right type of foil tape? Or could it be that the tape needs to actually stick to the foam pad? I have some copper foil tape on the way. I will try 6 layers of it just to see, but I don't hold much hope for it. I think my 2015 vintage BCD436HP is just one of those units that's not affected by this issue, as that fire ops signal is also unchanged if I run the radio on USB power with no batteries. It's sn 376Z58000xxx. I bought the radio new from Amazon. It's never been returned for any reason, still has the older bluish backlight and original RTC battery, both of which are still working fine after a year of average use.

.

If you read more of the posts on here you will see that the tape is related to what you are not hearing. Not so much what you are hearing. There are local UHF systems that the 436 does not hear at all. While other radios such as the 396XT and PRO97 receive just fine. With the shielded door the 436 now receives those systems. There are some videos posted that show when the shielded door is removed the signal completely disappears and when the door is reinstalled the signal returns. The shielding tape MUST go over the foam on the door. The tape you bought (as far as I can see) is not RF shielding tape.

 

[k3fs]

Curious has to how this thread never managed to get a sticky.

 

[ur20v]

Curious has to how this thread never managed to get a sticky.

Mixed results, for one. No standard of material used or method to application for another. And likely the site admins don't want to irritate Uniden or upman by appearing to take sides on the alleged issue that Uniden has pretty much ignored.

 

[wfinigan]

If they don't do something about this my days of automatically choosing uniden scanners are over.

 

[KevinC]

Mixed results, for one. No standard of material used or method to application for another. And likely the site admins don't want to irritate Uniden or upman by appearing to take sides on the alleged issue that Uniden has pretty much ignored.

Um...wrong...

Threads are typically "stuck" when the OP requests it be stuck.

 

[bearcat]

If they don't do something about this my days of automatically choosing uniden scanners are over.

I highly doubt they will do anything about it. They have not even acknowledged the issue. It is possible that they will find the issue and fix it in manufacturing going forward, but that still leaves us without clue as to the fix. Right now the shielded door is our best option.

 

[troymail]

I highly doubt they will do anything about it. They have not even acknowledged the issue. It is possible that they will find the issue and fix it in manufacturing going forward, but that still leaves us without clue as to the fix. Right now the shielded door is our best option.

Agree - we're already seeing that they've fixed the other "recall" hardware issues in the factory (someone recently sent in a unit to be fixed that UPMan indicated was already resolved on the production of his unit).

I suspect the fix for this (maybe already resolved in newer units?) doesn't meet the cost vs. benefit equation (kinda like what happened in the Firestone tire fisaco of year gone by).

This "flagship" line has had issue after issue in the hardware -- things you just can't fix with firmware releases....

Lesson learned - don't be in the front of the line for a new product unless you're ready to live with whatever you get...

 

[bearcat]

Agree - we're already seeing that they've fixed the other "recall" hardware issues in the factory (someone recently sent in a unit to be fixed that UPMan indicated was already resolved on the production of his unit).

I suspect the fix for this (maybe already resolved in newer units?) doesn't meet the cost vs. benefit equation (kinda like what happened in the Firestone tire fisaco of year gone by).

This "flagship" line has had issue after issue in the hardware -- things you just can't fix with firmware releases....

Lesson learned - don't be in the front of the line for a new product unless you're ready to live with whatever you get...

Are you saying the person was told that the UHF issue was on that returned unit? I am not sure I understood your post totally.

 

[troymail]

Are you saying the person was told that the UHF issue was on that returned unit? I am not sure I understood your post totally.

Sorry - no --

The user returned the unit(s?) for backlight and clock issues but was told those problems were resolved in the manufacturing of his unit (I took that to mean it was a fairly recently manufactured unit).

As we've discussed - Uniden has not acknowledged this interference problem (requiring copper or other tape on the battery door) that we're seeing - and I don' believe they ever will but I'll be the first to admit I was wrong if it happens.

 

[ChrisABQ]

I can verify on my 6800 series 436, that I need the shielding to hear the 400 mhz band. Night and day difference between using it and not using it.

 

[bearcat]

Sorry - no --

The user returned the unit(s?) for backlight and clock issues but was told those problems were resolved in the manufacturing of his unit (I took that to mean it was a fairly recently manufactured unit).

As we've discussed - Uniden has not acknowledged this interference problem (requiring copper or other tape on the battery door) that we're seeing - and I don' believe they ever will but I'll be the first to admit I was wrong if it happens.

I will be second to admit it unless I beat you to the punch (LOL)

 

[BOBRR]

Latest Theories ?

Hi,

Have read most of the multitude of Posts on this, but would like to ask:

So, is the consensus to use AL or Cu foil ?
Any idea why one is better than the other ?

Anybody try a "sandwich" of AL and Cu foil ?

Why should it be better if place on top of the foam, rather than underneath the foam ?

What's the latest theories on all of this ?

B.

 

[bearcat]

Hi,

Have read most of the multitude of Posts on this, but would like to ask:

So, is the consensus to use AL or Cu foil ?
Any idea why one is better than the other ?

Anybody try a "sandwich" of AL and Cu foil ?

Why should it be better if place on top of the foam, rather than underneath the foam ?

What's the latest theories on all of this ?

B.

I have tested all of the options. In my tests the RF/EMI spray with a strip of AL over the foam is absolutely the best. Second would be the AL. Third is the Cu. I have tried a combination of AL and Cu or a sandwich as you stated. It will help. I did not see any significant improvement over AL alone.. We do not have a scientific explanation as to why going over the foam works best, but it does. From what I have read. AL deflects or reflects RF. Cu absorbs RF. The latest theories are no different than what was found at the start of this thread. What we need is Uniden to tell us how to fix it, but I hold little hope of that happening.

I should have noted. With AL, I used two layers, Cu 6 layers and RF/EMI Spray 10 coats.

 

[jeffm77]

Bearcat, I have 6 layers of copper on my battery door and I think I still have the "noise". I emailed you last month, to see if you were going to make the local get together, as I wanted to get one of those "painted" battery doors off of you. Maybe you will be at January's meeting. Just let me know and the cost for one of the doors. And not to get off of subject, 2 weeks ago I got sick of the 436 and I broke down and bought the TRX-1. Let me tell you, it is great. I did the NXDN update on Thursday and it works great. I was torn between buying a new 436 or something different, so I went with the TRX-1. So far, so good. Maybe at the next meeting, you can bring your "sniffer" tools and I will have you check the TRX-1, to see if it has "noise", but I have not noticed and UHF problems.

 

[bearcat]

Bearcat, I have 6 layers of copper on my battery door and I think I still have the "noise". I emailed you last month, to see if you were going to make the local get together, as I wanted to get one of those "painted" battery doors off of you. Maybe you will be at January's meeting. Just let me know and the cost for one of the doors. And not to get off of subject, 2 weeks ago I got sick of the 436 and I broke down and bought the TRX-1. Let me tell you, it is great. I did the NXDN update on Thursday and it works great. I was torn between buying a new 436 or something different, so I went with the TRX-1. So far, so good. Maybe at the next meeting, you can bring your "sniffer" tools and I will have you check the TRX-1, to see if it has "noise", but I have not noticed and UHF problems.

I thought I gave you aluminum tape? Did you use it? That will work better than the copper. I really do not have enough people locally to justify the cost of the spray and doors. It would probably cost 30 bucks a door. Which would include the cost of buying the door, the spray and shipping for both. It is not something I am plan to get into. My spray is gone. It was used up during all the testing I did.

 

[jonwienke]

UHF Noise From Battery Compartment.

I did some testing to see how bad the UHF noise coming from the battery compartment of the 436 actually is, and what can be done to reduce or eliminate it.

I got a 10-foot USB extension cable and connected a RTL-SDR V3 dongle wearing the rubber duck from a MD-390, because it's a compact UHF antenna that screws directly to the SMA connector on the dongle with no adapters. Both AGC settings were turned off.

I tuned to a quiet area at 453.695 MHz and noted the noise floor with the dongle and antenna 5 feet away from the laptop and scanner. Then I laid the antenna across the battery compartment with the battery door removed, and noted that the noise floor rose about 15dB.

I moved the antenna so that its base was flush with the top of the scanner with the dongle against the left side of the case. The noise dropped to 7dB above the reference noise floor. I then tried raising the antenna so that its base was 1 inch above the top of the scanner, and the noise floor dropped to 3dB above the reference noise floor. Raising the antenna 2-3/4 inches above the top of the scanner decreased the noise floor to 2dB above the reference noise floor.

Then I put the antenna across the battery compartment with the door installed, which I lined with foil tape. The noise floor was about 3dB lower than with the door removed. I then repeated the previous readings with the battery door installed.With the antenna base flush with the top of the scanner, the noise level was 6dB above the reference. 1 inch up it was 2dB higher. 2-3/4 inches up, the noise was only 1dB above reference.

So lining the battery door with foil makes some difference, but not much--maybe 1-2dB.

What does make a significant difference is antenna height. I use the BNC adapter that came with the scanner, and put a BNC adapter on the stock duck antenna, so I can quickly switch between the dubber duck and base or mobile antennas which have BNC connectors. Putting the adapters in-line with the factory duck antenna raises it a trifle over 1-1/4" above the position it would be in if screwed directly to the scanner SMA connector. Raising the antenna by that amount decreases the interference noise by more than 4dB--double the improvement achieved by foiling the battery door.

Switching to a longer antenna made the difference practically disappear. I attached a Diamond RH77CA to the SDR and noted the noise floor, When I placed the scanner next to the dongle with the antenna at the same height as it would be if it was connected to the scanner, no change in the noise floor was noted.

Conclusions:
1. Using the BNC adapter on the scanner to raise the antenna further above the scanner reduces self-interference more than lining the battery door with foil. A SMA/BNC-BNC/SMA adapter chain reduced self-interference with the stock duck by about 4dB, definitely a beneficial tradeoff, even considering adapter losses.

2. Using a physically larger antenna such as the Diamond RH77CA (with a BNC connector) moves more of the antenna farther from the scanner, which reduces self-interference to negligible/undetectable levels.

3. Lining the battery door with foil helps a little, but not much compared to raising the antenna above the top of the scanner. Unless you're using the stock duck connected directly to the SMA connector, it's probably not worth the trouble.

 

[buddrousa]

So switching from the switching from the Remtronix SMA and using the factory SMA adapter and the Remtronix BNC would be even better. So is it fair to say that foil tape 1-2DB and the ADAPTER 4DB would help 5 to 6 DB that would be a great improvment.

 

[jonwienke]

Yes, and yes.