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

[troymail]

FWIW - My 436 is a "3" (2013?) model with backlight and battery mods... The addition of copper foil shielding results in NIGHT and DAY improvement in performance on UHF/DMR.

 

[KevinC]

FWIW - My 436 is a "3" (2013?) model with backlight and battery mods... The addition of copper foil shielding results in NIGHT and DAY improvement in performance on UHF/DMR.

Ditto on my date, mods and results.

 

[nosoup4u]

Has anyone disassembled the scanner and applied tape on the entire back case of the radio?

Sent from my Nexus 6 using Tapatalk

 

[bearcat]

Has anyone disassembled the scanner and applied tape on the entire back case of the radio?

Sent from my Nexus 6 using Tapatalk

Yes I did that before making the initial post. It did nothing. I have since removed it and nothing changed.

The battery door is the key. So Far

 

[k3fs]

Had the same poor UHF performance before and after backlight fix. I was hoping that improved reception would be an unexpected side effect of the fix, but it was not.

 

[deadvolvo1]

And your SN (minus the last 4)? And new backlight or old backlight?

(and can everyone post this from now on, as it appears to be part of the equation)

SN is 3726Z68001XXX.

It appears to have the new "uneven" and "yellowish" backlight according to the serial number and the appearance.

For the record, I'm using Eneloop Pro, stock antenna, stock MicroSD card, latest Beta firmware (1.11.16), and have both DMR and ProVoice upgrades.

 

[bearcat]

SN is 3726Z68001XXX.

It appears to have the new "uneven" and "yellowish" backlight according to the serial number and the appearance.

For the record, I'm using Eneloop Pro, stock antenna, stock MicroSD card, latest Beta firmware (1.11.16), and have both DMR and ProVoice upgrades.

Did or do you have the noise?

 

[Voyager]

I do not believe I ever stated that they all have the issue.

You may not have, but it has been implied by some that those without the issue are not looking, or are not being truthful about what they are seeing. I have been the target more than once of that when I suggested the issue was area-specific. I was accused of being "dismissive" of the issue. Of course I was dismissive that it is a problem in all units - because the unit I had did not have the issue. One I got earlier this year DOES have it. But this is all detailed above.

I have no idea which ones do and which ones do not. Mine was horrible on UHF compared to a 396 or Pro97 since day one. Pre-backlight fix and post-backlight fix.

Well that will complicate things a little. There must be some reason some have it and others do not. That will be key to narrowing the cause.

I do know that mine has improved a lot. Based on your findings Uniden must have made design changes that eliminated the problem.

Just the opposite. It's my original unit that is problem-free (circa 2013). The 2015 unit with the backlight fix DOES have the issue. But, as you stated yours is also a circa 2013 unit and has it, I would say that may prove that some units of the same design have it and others don't. As the cards are identical in both of my units, that should eliminate the card as the cause. What is left?

Myself and others have been beat up constantly for bringing up the UHF topic on these forums in the past.

Exactly my point. Not all units have the issue. Those like myself have been beaten up for saying it is not a design issue, as we don't have the issue. (and that continues this week).

The facts have now proven there is an issue. At least on some units.

Exactly. Now we have to find the commonality in units that have it vs units that do not. That may not be possible. Hopefully it is.

I can say that I have not seen one 436 that is stellar on UHF.

My 2013 unit performs about the same as previous units. Certainly there is not the great difference my 2015 unit exhibits.

I do not want to get into the date and serial number thing. That is for Uniden to identify.

There is no reason we can't do that, but as you and I both have very early units with one having the issue and one not, the SN appears to not be significant.

They own the records which show changes they have made to the production process. The next test would be a shielded door unit vs. a unit without the issue. Will UHF reception be the same?

Good question. I have proposed a test to you via direct eMail to compare units. But, I will say the foil got it close to the same as the unit without the issue. I didn't test it against a 396, however.

SN is 3726Z68001XXX.

It appears to have the new "uneven" and "yellowish" backlight according to the serial number and the appearance.

Yes, that's a 2016 unit and has the new backlight.

 

[KevinC]

This is really going to tick some off (not that I care), but I tested two units under identical conditions (same antenna - same frequency). BTW, the antenna I've been using for my tests is the Radio Shack Race Antenna (the 2" stubby), as that's my normal operating antenna. I don't care about range - I monitor locals where I am. This is used with the OEM SMA-BNC adapter.

Unit 1: 2015 SN with the backlight fix: Foil makes a definite improvement on one frequency, but little to no improvement on the other (this is the unit reported above).

Unit A (so as to not pick favorites): a 2013 unit without the backlight fix: The same piece of foil on the same frequencies had ZERO improvement, but I can tell that this unit performs similar to the unit above with the fix. This unit also fails the "finger test" and the "screwdriver test". In all trials, this unit simply does not have the same issues (at least not on the same frequencies/band).

This explains why I doubted that the scanner has the issues described or why I thought there were other factors involved (yes, I'm talking about you, Frank). Because the issues simply don't exist on the scanner I had AT THAT TIME.

Shortly after I got unit 1 is when some of us met and researched the issue (we met for other reasons, but Rich brought up this issue and 3 of us had 436s there and a couple 396s). I DID see the issue that night, but still thought it was location based until I did more research to find that I was now seeing similar issues.

Conclusion: The easy conclusion might be to say that the new backlight is causing the noise. But I don't know if others with the issue have new ones or old ones. I know Rich has a unit as old (or nearly so) as my 2013 unit, but has the issue. Rich - do you have the backlight fix? What card are you using (speaking of which Unit A and Unit 1 are BOTH using identical SanDisk Mobile SD cards, so that shoots that idea that it's the card causing it).

Certainly this proves that not all units have the issue, so this fix will not improve reception for everyone. So, those users who said they don't see it are NOT liars for fanboys, but likely do not have the issue.

I believe you are a Uniden beta tester, so your 2013 unit may actually be a pre-production radio and could explain a manufacturing difference.

 

[jeffm77]

What is this backlight issue I have never heard of the backlight issue the only issue I have ever heard of is the battery for the internal time clock? So the new were radios with the newer serial numbers manufactured 2016 do not have this UHF receive issue? I just don't understand how some people claim their radio works fine and others have the issue? I myself have the issue and two of my friends that have the radio also have the issue and we have radios manufactured from 2014. But when I apply the copper taped to the back of my battery door I do not see any difference except for maybe a few DMR stuff that I could not pick up a 4 comes in now. So I guess on my end that would be a little Improvement. But I am going to continue to do some more tests to see if I can fix it better.

 

[Voyager]

I believe you are a Uniden beta tester, so your 2013 unit may actually be a pre-production radio and could explain a manufacturing difference.

Nope. It's a production unit. Others have reported not having the issue as well.

What is this backlight issue I have never heard of the backlight issue the only issue I have ever heard of is the battery for the internal time clock?

The backlight dims over time. Lots of info here on RR about the issue.

So the new were radios with the newer serial numbers manufactured 2016 do not have this UHF receive issue?

No - only some newer units seem to have it. Some older units have it. So far there has been no distinct cause found as to why some have it and others don't.

I just don't understand how some people claim their radio works fine and others have the issue?

That's just the way it is. Until some reason is found, it might be manufacturing tolerances (although that's a pretty big variance for some to have it and others do not at all).

I myself have the issue and two of my friends that have the radio also have the issue and we have radios manufactured from 2014. But when I apply the copper taped to the back of my battery door I do not see any difference except for maybe a few DMR stuff that I could not pick up a 4 comes in now. So I guess on my end that would be a little Improvement. But I am going to continue to do some more tests to see if I can fix it better.

As stated, I have one that has it and one that does not. On the one that has it, the foil was better on some frequencies and worse on others (or at last no better). I thought it might be backlight related but others have proven that wrong, as they had it pre-and post-backlight (which is interesting since the entire front board was changed and it is coming from that board).

There has to be a cause - it just hasn't been found yet - even if there are certain production lines that are the common thread. (assuming they have more than one). Worst case would be a part tolerance issue which means the issue will be spread randomly across the units. That would be nearly impossible to identify.

To summarize so far:
Backlight - ruled out
Clock fix - ruled out (since that was changed with the backlight)
New front board vs old - ruled out (same reason as above) (assumed a design change)
SD Card - ruled out
SN based - ruled out
Batteries - ruled out

We are running out of commonalities which leaves random tolerances.

Recording (replay) - ?????? I know my 2013 unit without is still using the recording feature - as I believe is my newer unit.

Firmware - ??????? Both of my units are running recent firmware (but not identical).

FLs vs main dB - both of my units are using FLs only, and are identical in programming.

If it is something in the write speed of the SD card (not the card itself), a firmware change could fix that.

Other ideas?

 

[W4KRR]

Anyone tried removing the batteries altogether and powering the scanner with a USB cable?

 

[deadvolvo1]

Did or do you have the noise?

Short answer: Yes.

However, until I tried the "touch" test, I wasn't sure. Even then, I had to tap rhythmically on the middle and bottom vs. middle and top batteries. Only then could I notice a difference in the noise floor.

The difference between the 436HP I have and my 396XT and 396T is negligible. The same applies compared to an Icom R5. I don't know whether it is environmental or what, but I don't seem to be "missing" anything in the UHF band. I'm not sure how I would notice because there are a million places in the UHF band for these scanners to stop. In particular, this environment (zipcode 19107) is full of very strong pager systems and other very strong nearby digital signals which play havoc with these small receivers. Making matters even worse, I'm line of sight from KIH28. The stock antennas are the max I can use with handheld receivers here. Normally I use a Diamond SRH805S to get the best reception of the Philadelphia P25 Phase II system, and I can typically receive it just fine without an antenna.

Thus the only way to tell is to compare A/B with a weak signal in the UHF band, and that invites images from other signals into the methodology. In that case, the 436HP beat out both 396's "no contest" because of better image rejection on the 436HP, and possibly better squelch implementation.

The bottom line is that while I am 100% confident now that my unit "has it", it still feels like it is far from a serious problem for this unit in this environment.

 

[darunimal]

We all should be testing this with the sma-bnc adapter without an antenna on FM w a 5khz step and then 6.25khz

We all have charging circuits, we all have 2 boards, we all have a front speaker, battery Voltage may play a large part in this, but also the discriminator is the most likely noise area to introduce noise between the 430-470mhz range.

There is a shield inside that may need to continued down to the bottom part of the daughter board w/o contacting any surface mounted components.

AND/OR

One solution might be a snubber on the middle batteries positive terminal but this may have adverse affect on charging and discharging, and may introduce its own noise.

 

[KevinC]

I believe you are a Uniden beta tester, so your 2013 unit may actually be a pre-production radio and could explain a manufacturing difference.

Nope. It's a production unit. Others have reported not having the issue as well.

Ok, it was worth a try.

I'm open to any suggestions people have to try to narrow down what the cause is, but the foil works so well it almost isn't worth it.

 

[deadvolvo1]

Other ideas?

Battery state-of-charge?

 

[KevinC]

Anyone tried removing the batteries altogether and powering the scanner with a USB cable?

Yes, but without the batteries to radiate the noise it's greatly suppressed, but still present....especially if you "sniff" around the center battery contact.

 

[KevinC]

Battery state-of-charge?

It's present with no batteries.

 

[Voyager]

Battery state-of-charge?

I'm sure Rich or Frank would have noticed an improvement with the charge state if it varied with it. But good idea. I'm sure one or both of them will confirm this.

 

[Voyager]

We all should be testing this with the sma-bnc adapter without an antenna on FM w a 5khz step and then 6.25khz

IFX on/off = no difference.

Step = no difference (aside from the off-frequency distortion, but the noise is still there)

Without an antenna - Same issue. I generated a weak signal on 460 MHz after I removed the antenna. The noise was still present and was removed using the "finger test". I guess that might contradict Rich's original test using the remote antenna. I can try that test later.

OK. I just duplicated Rich's test with the same results. I moved the antenna to the end of a 3' BNC jumper and the finger test made zero difference on a signal that does change with the same antenna on the scanner. I'm not sure what this says when viewed with the above test. I guess it says the weak signal above was still picked up on the SMA connector (which means the scanner RX circuit is well shielded).

We all have charging circuits, we all have 2 boards, we all have a front speaker, battery Voltage may play a large part in this, but also the discriminator is the most likely noise area to introduce noise between the 430-470mhz range.

We all have them. Do you know for a fact they are of identical design?

Also, it is clearly coming in the antenna. Rich proved that in another thread since a remote antenna does not exhibit the issue. I confirmed that as stated above. BTW, moving the antenna on the jumper near the scanner resulted in the noise returning.

There is a shield inside that may need to continued down to the bottom part of the daughter board w/o contacting any surface mounted components.

Rich tried shielding the entire rear with no change. But it seems clear it is coming in the antenna port since moving the antenna away eliminates the issue.