BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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It would be really nice to know if those units have the battery compartment noise.
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Has anybody actually used a spectrum analyzer and pickup antenna near the scanner to see the problem? I don't have a 436 but I do have a spectrum analyzer with various pick up antennas and preamps. If anyone is in the Los Angeles area and wants to test their 436 I would be willing to use my analyzer on it.
Edit: I did not read all 26 pages on this problem but in my opinion it could be Uniden uses a switching power supply to provide various voltages wtihin the radio and that switching supply is poorly decoupled from its input source, the battery. Just my guess, but if true a broad band choke between the battery and the rest of the radio could help. These wide band chokes are small ferrite beads with multiple holes and about 5 turns of wire through them makes a very effective choke at VHF/UHF.
prcguy
Edit: I did not read all 26 pages on this problem but in my opinion it could be Uniden uses a switching power supply to provide various voltages wtihin the radio and that switching supply is poorly decoupled from its input source, the battery. Just my guess, but if true a broad band choke between the battery and the rest of the radio could help. These wide band chokes are small ferrite beads with multiple holes and about 5 turns of wire through them makes a very effective choke at VHF/UHF.
prcguy
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I am not really sure what it is? If it is an RF/EMI shielding product it should work. Keep in mind a sprayed/coated door still needs a strip of aluminum or copper shielding on top of the foam. The spray is the most effective product I tested and I have tried them all.
I'm not sure if this will help but I used the copper tape on my battery door and then Uniden then fixed the clock issue and now my 436 seems to pick up a lot better then it did when I got it, also I can pick up dmr systems and p25 systems that are at least 20 plus miles away.
dcisive
Member
Got Egg On My Face
I was in denial and denied that the 436 had this issue with the battery door not providing proper signal insulation from the battery compartment as it supposedly interacts with the antenna. Well....yesterday I went and cut up some industrial strength foil my wife had from a relative that is in the food industry. This stuff is over twice as thick as the typical foil you might get at the store as heavy duty.
I cut a full length and folded it until it was about oh...6 or 8 thicknesses. Cut it so it fit the door and over the foam pad corner to corner end to end. I then scanned in the 140mhz range. When it stopped on a weak signal that was just a signal no speaking, I brought the treated door up to the batteries. As I pressed it against the batteries snapping it into place, I would say the noise floor dropped about 2 1/2 times what it was as soon as I removed the door. So with the door in place I continued the scan. When it came Upon another fairly weak signal and stopped, I removed the door. Guess what. The signal literally went away. Put the door back on and voila' it returned. Yikes.
So then I tried to scan in the airport frequencies (120-128mhz range) and this using the new Remtronix 800mhz antenna which is the manufacturer in Japan that makes the Radio Shack one that is so well respected. It's identical and in my case a SMA one as well for best fit without adapters. The result was identical. When it stopped on channels I'd typically never even received before, I rremoved the door and they either got extremely weak or disappeared altogether. Hmm
So last but not least I scanned the 800mhz range. Not expecting any difference......well.....once again it did lower the noise floor. Not quite as dramatically as the 120 or 400mhz range, BUT still I'd say it diminished the noise by at least half. So guess I'm sold on the idea that indeed the radio needs this mod to do it's best. I've lightly taped the back of the foil to have it remain in place and I'll be leaving it on. Can't argue with success. I guess Uniden is desiring to ignore this one. I like the idea of the spray or paint on nickel or whatever was used by another user here. But I'm not sure exactly what it is or where to get it.
I was in denial and denied that the 436 had this issue with the battery door not providing proper signal insulation from the battery compartment as it supposedly interacts with the antenna. Well....yesterday I went and cut up some industrial strength foil my wife had from a relative that is in the food industry. This stuff is over twice as thick as the typical foil you might get at the store as heavy duty.
I cut a full length and folded it until it was about oh...6 or 8 thicknesses. Cut it so it fit the door and over the foam pad corner to corner end to end. I then scanned in the 140mhz range. When it stopped on a weak signal that was just a signal no speaking, I brought the treated door up to the batteries. As I pressed it against the batteries snapping it into place, I would say the noise floor dropped about 2 1/2 times what it was as soon as I removed the door. So with the door in place I continued the scan. When it came Upon another fairly weak signal and stopped, I removed the door. Guess what. The signal literally went away. Put the door back on and voila' it returned. Yikes.
So then I tried to scan in the airport frequencies (120-128mhz range) and this using the new Remtronix 800mhz antenna which is the manufacturer in Japan that makes the Radio Shack one that is so well respected. It's identical and in my case a SMA one as well for best fit without adapters. The result was identical. When it stopped on channels I'd typically never even received before, I rremoved the door and they either got extremely weak or disappeared altogether. Hmm
So last but not least I scanned the 800mhz range. Not expecting any difference......well.....once again it did lower the noise floor. Not quite as dramatically as the 120 or 400mhz range, BUT still I'd say it diminished the noise by at least half. So guess I'm sold on the idea that indeed the radio needs this mod to do it's best. I've lightly taped the back of the foil to have it remain in place and I'll be leaving it on. Can't argue with success. I guess Uniden is desiring to ignore this one. I like the idea of the spray or paint on nickel or whatever was used by another user here. But I'm not sure exactly what it is or where to get it.
When did you have clock issue fixed?
It is not cheap, but here is the link to what I used. I put 10 coats on my doors. Whether 1 coat or 10 makes a difference I really do not know but 10 works. You still need to put some shielding tape on top of the foam. It was worth every penny to me. Remove the foam when you spray. Make sure you use some painters tape on the outside of the case to prevent over spray
MG Chemicals Super Shield Nickel Conductive Aerosol 12 OZ | 841-340G (841340G) | MG Chemicals
UHF Noise Issue Resolved (Hopefully)
If you have an original shipment 436 that has not been back for the clock/display issue. These findings probably do not apply to you. I found some pictures on prior threads showing the display board from those units and it is very different than the ones that were installed during the repair campaign.
I was able to find a 436 that does not exhibit any noise in the battery compartment. The radio has a 2016 serial number. I compared the display boards on both units and found a capacitor that is missing on my 2013 unit. I accept no responsibility for those who wish to open their unit and check for the capacitor. DO SO AT YOUR OWN RISK. Once you remove the front cover, then remove the display board. Flip over the display board and look in the area the of top right battery terminal. You should see the letters TDO on the circuit board. On the 2013 unit there are two solder pads without any component installed. On the 2016 model those pads have a capacitor soldered in place. I have no idea on the value of the capacitor. So anyone who can help with that value it would be great.
I think we will be on our own on getting this done. I am sure Uniden will say that specifications and parts can be changed at any time and many folks on the list do not even agree there is an issue. So am not personally interested in the attack Uniden campaign. I just want the thing to work right. Obviously Uniden has made some changes on these boards.
If you have an original shipment 436 that has not been back for the clock/display issue. These findings probably do not apply to you. I found some pictures on prior threads showing the display board from those units and it is very different than the ones that were installed during the repair campaign.
I was able to find a 436 that does not exhibit any noise in the battery compartment. The radio has a 2016 serial number. I compared the display boards on both units and found a capacitor that is missing on my 2013 unit. I accept no responsibility for those who wish to open their unit and check for the capacitor. DO SO AT YOUR OWN RISK. Once you remove the front cover, then remove the display board. Flip over the display board and look in the area the of top right battery terminal. You should see the letters TDO on the circuit board. On the 2013 unit there are two solder pads without any component installed. On the 2016 model those pads have a capacitor soldered in place. I have no idea on the value of the capacitor. So anyone who can help with that value it would be great.
I think we will be on our own on getting this done. I am sure Uniden will say that specifications and parts can be changed at any time and many folks on the list do not even agree there is an issue. So am not personally interested in the attack Uniden campaign. I just want the thing to work right. Obviously Uniden has made some changes on these boards.
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Is there a schematic diagram that shows where the part is in the circuit? Is it possible to safely and temporarily unsolder one lead of the cap and test for noise?
prcguy
prcguy
k3fs
Member
See attached pic. The area is clearly marked C1. Makes sense to put a capacitor there to filter noise from the power supply.There is solder on the pads, but no component. This seems to be common in the radios. The area is at the very top of the picture right next to the battery terminal
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k3fs
Member
This may explain the silence. The capacitor was missing in earlier models that show the noise. Now it is there, and the noise is not there. Obviously Uniden is aware of the problem.
Bearcat is far braver than I. I do not have an SMD capacitor to try. I am not sure there is enough clearance due to the case and the shield to put a regular capacitor in the spot. It is awfully close to the resistor right next to it as well.
Bearcat is far braver than I. I do not have an SMD capacitor to try. I am not sure there is enough clearance due to the case and the shield to put a regular capacitor in the spot. It is awfully close to the resistor right next to it as well.
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I have an old one. 376Z38000XXX series number. I'll drop a .001 cap in there if it's missing and see what happens.
Well, mine doesn't even have spots for those components. The pads don't exist.
I'm guessing your's hasn't had the RTC repair done?
No, has't.
I wonder if that's a coil next to it or is it a 0 ohm resistor with part of the 0 missing?
I assume the cap is connected to that CLK line. Maybe it's filtering noise from that. What's odd is all the same silkscreen markings are there but the actual pads aren't. Maybe they forgot to add them in.
jeffm77
Member
I opened my 436 today. I don't have the capacitor either. There's solder pads, but nothing there. Interesting. Hmmmmm.... i thought about buying a new 436 hoping to get a newer model.
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