I am not a Uniden basher either, but I am the consumer and expect to get what I pay for. I agree totally something was missed. The 396xt runs circles around the unshielded 436. The only radios I own are Uniden. Including a new CB, I should note I have never spoken a word on it. I do have a Pro97 but only bought that radio because if has a great LCN finder for LTR systems. If Uniden acknowledges the problem they may be faced with fixing it. I am being an optimist and hoping that they are working on the fix for it. Until then the radio can be turned into a super radio while we wait. I still would love to hear what Tech support has to say. Paul has never joined this thread to deny or acknowledge the issue. So we just wait and see.
BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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troymail
Silent Key
So, it's been a few weeks since I added my copper shielding tape over the foam pad. I had a feeling that the reception has been steadily decreasing and I was hearing less UHF/DMR over time. Last week, I decided to add a third layer and thought I noticed a slight improvement. In the past day or two, it seemed to be going silent again so tonight, I added a stack of four half inch wide strips over the copper tape that is covering the foam pad ... and reception quickly improved.
I think over time, the copper tape is helping to further compress the foam pad more and more each time I remove the battery door to replace the dead batteries. Adding the strips restores the contact with the batteries.
Just thought I'd pass it on...
I think over time, the copper tape is helping to further compress the foam pad more and more each time I remove the battery door to replace the dead batteries. Adding the strips restores the contact with the batteries.
Just thought I'd pass it on...
Been using copper foil for 2 weeks. Overall impression is some improvement but on VHF/UHF with any duck antenna, including Diamoncd 77CAs, my 396 and TRX1 still quite a bit more sensitive. With outdoor antenna, different story. But I don't usually buy handhelds to be used as base radios.
k3fs
Member
New battery doors do not have the foam. There is no difference in those doors compared to those that do have the foam when unshielded. Lesser results were achieved when shielding was applied to the foamless doors as compared to shielding applied over the foam. Place a piece of foam on those doors, and place shielding over the foam, and results are the same as the foamed original doors.
Perhaps Bearcat can elaborate on this a little more.
I too hope that Uniden will do the right thing and fix this, but as of yet they have failed to admit there is a problem. Despite their own code of conduct.
I will assume you went over the foam with your copper. Try more layers of copper. I currently am using a door that I sprayed with RF/EMI spray paint (10 coats) and a piece of aluminum shielding tape over the foam and my 436 performs Identical to my 396. The door I have with just aluminum tape shielding is just about as good.
A door without any shielding or foam is just as bad as the door with foam and no shielding. I have even sprayed one with RF/EMI spray and no foam and that is of little value. For whatever reason you need that shielding tape pressing on the batteries. That being said I have tried an unshielded door with aluminum tape over the foam and there was a bit of improvement but nothing like shielding the door.
woodpecker
Member
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I just ran a sweep of my 436 using a signal hound spectrum analyser from 300MHz to 500MHz with the scale set to 2dB / div, I can't detect any change in RF nose floor level from the battery compartment area with the 436 on or off.
The 436 had an RH77CA antenna connected, the analyser had 4 inch rod as its measuring antenna.
I don't have much in the way of local strong UHF here so there is nothing that would overload it with a handheld antenna. I keyed up a dstar handheld on 440MHz and tuned the 436 to that frequency but still didn't see any change in the noise floor that was noticeable on 2dB/div even.
Those that are seeing this problem, is it the whole scanner is overloaded with strong UHF and its re-radiating out a load of intermodulation products??
The 436 had an RH77CA antenna connected, the analyser had 4 inch rod as its measuring antenna.
I don't have much in the way of local strong UHF here so there is nothing that would overload it with a handheld antenna. I keyed up a dstar handheld on 440MHz and tuned the 436 to that frequency but still didn't see any change in the noise floor that was noticeable on 2dB/div even.
Those that are seeing this problem, is it the whole scanner is overloaded with strong UHF and its re-radiating out a load of intermodulation products??
We really do not know what is causing it. I would only rule out intermod because I have been in two very remote RF free areas if you will. I could still see the noise. Try to increase the gain or maybe preamp on your SA. Probe the middle battery on the positive side. See if you see anything. What is the date of mfg on your radio? Try this also take you Dstar radio tune it to 460.000 open the squelch and do the same middle battery probe. Actually touch the antenna to the middle battery. See if the sql noise on the Dstar radio changes in level or tone. I would love to know what is different on the radios that do not have it.
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I would also say you should do a much wider frequency scan at the battery area, while the noise appears to affect UHF reception, the noise source may be a much lower frequency that is getting into an internal mixer or something based on the symptoms people are reporting.
I am sure that could very well be. I personally do not have the test equipment it would take to pin point the issue. I am hoping that Uniden will identify the issue and the fix. For now I at least know that some shielding on the foam and battery case do the trick.
woodpecker
Member
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I purchased my 436 Easter 2015 so it would have been manufactured some time before that.
One thing I forgot is that I have modded mine with a discrimantor tap see here:-
http://forums.radioreference.com/uniden-tavern/330695-bcd436hp-discriminator-mod.html
I used one pole of the earphone jack for the tap, at the time I remember having a bit of a problem with noise when using the tap hooked up to a USB sound card, I found the shield of the audio jack not being grounded was the culprit so I bonded it to the PCB ground in the 436, I don't know what effect this may have had on any other noise.
I cannot say I ever really noticed a UHF problem on mine, you could try grounding the audio jack without taking the 436 apart, just hook the audio shield on the headphone output to the antenna ground.
I bought my 436hp the first week they were introduced and never had a problem with uhf or vhf reception. It seems like after the new updates is when I noticed a performance drop.
Sent from my VS986 using Tapatalk
Sent from my VS986 using Tapatalk
troymail
Silent Key
Me too - but that's probably because I was only listening to 700/800 Mhz before the DMR update.
I took a vacation and went back where I use to live for a week and I notice where I stay at no matter I do signal wasn't good as like the cell phone had no signal. I was staying at a friends house near the airport. I go like 1/2 mile towards the main highway I still had the copper tape on the door.
I am not exactly sure what you are telling us. Did you find improvement on UHF with the copper door?
UHF/VHF picked up good with the tape on in the area I was staying at. I was hoping the 800 system would have been better in the area I was at. But I was picking up a 800 system with 1 bar that was 50 miles away.
Someone in a few previous posts mentioned they hadn't seen visually how this interference looks. Using a NooElec R820T2 SDR I placed the BCD436HP next to the small stock antenna of the SDR. Attached are pictures with the scanner off and then with the scanner on. There is an increase in the noise floor of 12 dB on 460.000 MHz. This test was with a small filter in the battery case as suggested by others, when the filter was removed I got another 1.6 dB of additional noise.
Sad part is the $30 SDR receives far better than the BCD436HP, in many aspects.
Thanks for reading - Steve
Sad part is the $30 SDR receives far better than the BCD436HP, in many aspects.
Thanks for reading - Steve
I would consider the 436 to be superior on 800 mhz. I would expect you were just too far away from the system. UHF has been the area of poor performance, but we all know that can be fixed with some shielding.
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