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

[jonwienke]

Spoken like a loyal Uniden employee. Are you one?

You have no proof seth21w is shilling for Uniden, paid or unpaid. Disagreeing with you doesn't make anyone a shill for anyone.

Should people stick their head in the sand and accept a poorly performing receiver or be pro active and rule out they have an affected radio? "Most likely" doesn't cut it here and people should be able to determine if they have the noise problem via visual inspection of the radio or an easy to perform receiver test.

There are ways to objectively test how much self-interference noise affects reception. I've outlined one easy to perform test method most any user can perform (if they are willing to spend $20 or less on a RTL-SDR stick), and demonstrated that the problem isn't necessarily the "sky is falling" type of problem you and others are claiming, at least with my units.

IMO this discussion would be a lot more productive if people confine themselves to facts and data rather than grandiose hyperbole and paranoid accusations. Test your own scanner(s), and see how closely your results track with mine. If you don't think the test procedure I outlined is valid, then propose your own, with an explanation of what shortcomings it addresses. Either way, test your scanner(s) and post the test results, so that others can compare notes.

 

[prcguy]

A totally agree and since Uniden will not publish anything that would identify if you have the problem you have to test it yourself to find out. How would anyone on a forum know that it most likely doesn't have a problem without looking at it?
prcguy

You have no proof seth21w is shilling for Uniden, paid or unpaid. Disagreeing with you doesn't make anyone a shill for anyone.



There are ways to objectively test how much self-interference noise affects reception. I've outlined one easy to perform test method most any user can perform (if they are willing to spend $20 or less on a RTL-SDR stick), and demonstrated that the problem isn't necessarily the "sky is falling" type of problem you and others are claiming, at least with my units.

IMO this discussion would be a lot more productive if people confine themselves to facts and data rather than grandiose hyperbole and paranoid accusations. Test your own scanner(s), and see how closely your results track with mine. If you don't think the test procedure I outlined is valid, then propose your own, with an explanation of what shortcomings it addresses. Either way, test your scanner(s) and post the test results, so that others can compare notes.

 

[jonwienke]

A totally agree and since Uniden will not publish anything that would identify if you have the problem you have to test it yourself to find out. How would anyone on a forum know that it most likely doesn't have a problem without looking at it?
prcguy

In this case, knowing the scanner has a recent serial number that seems to include the resistor and capacitor.

 

[dcisive]

I haven't dismantled my 436 but most certainly have confirmed it's performance is greatly enhanced by my measuring and folding just the right size that fits the inside of the battery compartment cover perfectly. I folded over probably about the equivalent of 8 layers of a commercial grade foil my wife got from her relative that works in the food industry. I simply taped it on both sides that contact the door and indeed it was a tight fit initially, but now has conformed nicely to the pressure where the pad contacts the batteries. I did the scan in the 400mhz range and there was a business channel that was barely received at all that it initially stopped on but was so weak and noisy I just hit the hold button. Then by placing the foil covered cover as it got closer to the battery compartment it improved by like 50%, putting good pressure on it and snapping it into place literally gave me near 100% quieting as compared to without the foil where I could barely hear it at all. So YES foil does and can work just fine under these circumstances obviously. I'll get over not having a cap or resistor I guess as it's working so nicely and it's no skin off my nose to just be leaving that perfect fitted pad of aluminum on the cover. It's not that big of a deal to me as long as I get the results........and I DO. I also picked up a Remtronix 800mhz antenna which is the same Japanese manufacturer that makes the Radio Shack 800mhz antenna we all know and love. I elected to go with the SMA for a more perfect match with the 436. I have exhaustively tested it against using the BNC adapter and RS model and there is absolutely NO signal quality difference at ALL frequencies, and believe me I tried them ALL from 120mhz on up to the upper 900mhz range. The Remtronix actually does a fine job across the board not limited to just the 800-900mhz range at all. I even get distant airport stuff in the 130mhz range using it so no complaints. Sure seems there are varying results from some folks here with both the foil vs. copper as well as the antennas used. Oh well. I've completed my tests and this is working for me.

 

[bearcat]

Folks take a look at this Youtube video. This shows the results of using a shielded door and/or adding the capacitor. I experience the exact same results as the guy that made this video. This is how drastic the improvement can be on WEAK signals.

https://www.youtube.com/watch?v=-5OiNho416U

 

[mancow]

I probed the spot under the batteries named CPU power. It's nasty with that same wide band noise. I think it could be another source in that area by the sd card.

After messing with the foil on the door I started wondering if it's doing two things, blocking the noise from radiating and providing a counterpoise which brings in more legitimate signal. The two in concert improve reception.

Try removing the cover and place your fingers horizontally across the batteries and push fairly hard. The result is similar to the foil door.

 

[Ubbe]

After messing with the foil on the door I started wondering if it's doing two things, blocking the noise from radiating and providing a counterpoise which brings in more legitimate signal. The two in concert improve reception.

If it wasn't for the fact that people are convinced that adding a capacitor helps, I would say that almost everything points to an antenna counterpoise issue. Adding an adapter between scanner and antenna will make the counterpoise longer, adding foil in different ways will make the counterpoise better, using an external antenna will totally eliminate the internal counterpoise problem.

/Ubbe

 

[bearcat]

If it wasn't for the fact that people are convinced that adding a capacitor helps, I would say that almost everything points to an antenna counterpoise issue. Adding an adapter between scanner and antenna will make the counterpoise longer, adding foil in different ways will make the counterpoise better, using an external antenna will totally eliminate the internal counterpoise problem.

/Ubbe

I am not sure if it was discussed prior, but during the investigation into the noise a counterpoise was tested. I put a piece of wire about the length of the radio on the ground side of the antenna and attached it to the back of the radio. It did not work. Just to clarify the capacitor is now being installed by Uniden from the factory and the noise is gone. It is not really a modification. The solder pads for the cap have been there all along starting with display board 1.09.02.

 

[chill30240]

I'm having the same problem and my 436's warranty ran out last Dec 5th. How did you go about getting Uniden to install the capacitor and what's the charge, if any, for that to be done.

Thanks

 

[prcguy]

It seems to be proven that its an internally generated noise problem, mancow probed it with an SDR spectrum analyzer and it picks up noise in the affected UHF range. Its not uncommon, I've seen similar internal noise problems in other types of radios.
prcguy

If it wasn't for the fact that people are convinced that adding a capacitor helps, I would say that almost everything points to an antenna counterpoise issue. Adding an adapter between scanner and antenna will make the counterpoise longer, adding foil in different ways will make the counterpoise better, using an external antenna will totally eliminate the internal counterpoise problem.

/Ubbe

 

[dcisive]

For what it's worth I did try to determine if using the BNC adapter with the Radio Shack 800mhz antenna had ANY improvements or advantages over the Remtronix 800mhz antenna I got from Universal Radio. They are manufactured by the SAME Japanese manufacturer. The difference is I opted for a SMA mount on the Remtronix vs. the BNC adapted Radio Shack. I scanned from 120mhz up to 930mhz. There was absolutely not one iota of difference between the quieting between them. They are identical. So I do NOT believe the adapter making the antenna tiny bit further from the radio makes ANY difference whatsoever. This of course is AFTER I've applied the 8 layered block taped onto the inside of the battery door, which made a tremendous difference indeed. Like from 1 bar to 5 bars and noise to near flawless quieting. Let alone reception of a good number of frequencies that without the foil are flat out not even there. Oh well..........I'm not disturbed about having that pad permanently installed as it's not a big deal. At least it works

 

[bearcat]

I'm having the same problem and my 436's warranty ran out last Dec 5th. How did you go about getting Uniden to install the capacitor and what's the charge, if any, for that to be done.

Thanks

Uniden has never acknowledge the issue. I think a call to Uniden service would be your best bet. Tell them you want them to install the missing capacitor. It would be interesting to hear what they say.

 

[k3fs]

Any one have an idea on size code for the capacitor? I got these :
MURATA Multilayer Ceramic Capacitor 0.01uF 100V X7R 1311 20% SMD **NEW** Qty.100 | eBay

Size code 1311. These are very likely too thick, and will get in the way of reattaching board to case.

I am looking at these. I'm guessing these will fit in nicely
PANASONIC Multilayer Ceramic Chip Capacitor 0.01uF 50V Y5V 0603 SMD 100/PKG | eBay

They are size code 0603.

FWIW, there is continuity from capacitor to coil, and to the top battery negative terminal, and middle battery positive terminal. The capacitor pad closest to the edge of the board has continuity to ground. With the capacitor installed the capacitor and coil have continuity to middle battery negative and bottom battery positive. There is no longer continuity to the top battery.

There may be improved VHF reception with capacitor installed, as compared to shielded door. Shielded door had done a little to improve VHF, but not as much as it does on UHF.

Using the SMA to BNC adapter made no improvement with any antenna I tried.

Some notes about boards and serial numbers. 2015 models can have a board V01.09.00. These boards also have the component that is likely a coil mounted next to the capacitor. The capacitor is not installed.

Serial numbers are a little odd. The first number after the Z is manufacture year. The last digits following the 8 are the serial number. Numbers restart for each manufacture year. For example we had a 2014 production with 8800 number. A 2016 production number with 5600. You cannot go by last four numbers alone.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.

 

[pro92b]

http://forums.radioreference.com/un...noise-battery-compartment-36.html#post2741956

In the post referenced above Bearcat measured the capacitor to be 1/16" x 1/32" which corresponds to 0603 size.

I would use dielectric type X7R instead of the poorer performing Y5V. The link below would be my choice.

http://www.mouser.com/ProductDetail...EpiMZZMsh%2b1woXyUXj70UFERBp%2b3YP1bwVZl/9gk=

Has anyone actually measured the capacitance of the part that Uniden is now populating on the board or is .01uF just a guess?

 

[bearcat]

http://forums.radioreference.com/un...noise-battery-compartment-36.html#post2741956

In the post referenced above Bearcat measured the capacitor to be 1/16" x 1/32" which corresponds to 0603 size.

I would use dielectric type X7R instead of the poorer performing Y5V. The link below would be my choice.

http://www.mouser.com/ProductDetail...EpiMZZMsh%2b1woXyUXj70UFERBp%2b3YP1bwVZl/9gk=

Has anyone actually measured the capacitance of the part that Uniden is now populating on the board or is .01uF just a guess?

.01uf was a guess, but an educated guess. I did some research on filtering capacitors and found .01 and .1 were popular values. The .01 did eliminate the noise.

I have nothing to magnify the cap that I found in the factory unit. So I do not know the actual value.

 

[pro92b]

.01uf was a guess, but an educated guess. I did some research on filtering capacitors and found .01 and .1 were popular values. The .01 did eliminate the noise.

I have nothing to magnify the cap that I found in the factory unit. So I do not know the actual value.

Capacitors are not ideal components and they reach a point where their impedance is actually inductive if you go up in frequency enough. Larger capacitance value means this transition or resonance frequency is lower. To filter VHF and UHF frequencies it may be more effective to use a lower capacitance that has a higher frequency self resonance.

Murata publishes graphs of capacitor impedance such as the one for a .001uF capacitor at Capacitors | details for GRM188R11H102KA01# | Murata

The .001uF self resonance point is at 240 MHz according to the graph. For .01uF it is 70 MHz and for .1uF it is 24 MHz. Noise filtering is still effective somewhat beyond the resonance point but the .1uF is probably too large to be effective at filtering UHF noise. The best value is probably between .01uF and 100pF. Beyond the capacitor, the copper traces on the circuit board will also affect the resonant frequency.

I don't doubt that you significantly reduced the noise with .01uF, but it is unlikely that .01uF is optimal for noise reduction since it is just a guess. We also don't know how much work Uniden did to optimize their choice of capacitor value, whatever that value is.

Capacitors of 0603 size are often not marked with a value due to the small size of the component. That leaves measurement with a capacitance meter as the only way to tell its value.

 

[chill30240]

Uniden has never acknowledge the issue. I think a call to Uniden service would be your best bet. Tell them you want them to install the missing capacitor. It would be interesting to hear what they say.

The sad part is that Uniden probably never will acknowledge the issue. Large companies tend to do that. From 1984 to 2002 I was a System Technician and Senior Headend Technician at he local cable company where I live. Back in the middle 90's I ran several service calls pertaining to bad reception. All the TVs were RCA and it didn't matter if was a portable or floor model. After they had been on for a while all the channels in the 30s and 40s went snowy had lines running through them and sounded like someone was blowing a trumpet in the background. After several months of me having to tell the customers it was their TV and not the cable system I stopped in at one of our local repair shops here in town. I explained the problem I was seeing to the owner and low and behold he showed me the first TV I saw it on. It was in the shop getting repaired. Turns out that a capacitor on the tuner board was going bad and RCA had known about it for some time. With thousands in their warehouses and what already been sold there was no way they were going to just to volunteer to repair all of those. So they decided to fix the ones that acted up within the 1 year warranty period free of charge and the ones that acted up after that would be charged. It usually took approx. a year some times 15 months to act up. As soon as they found out about the problem it was rectified in the factory but the ones that had already left the line went to unsuspecting customers. I would be willing to bet that Uniden knows about the problem with these units and will probably handle them the same way. After all the new boards have the capacitor don't they and don't suffer the noise problem? Its sad that as much as these things cost we have to resort to tape and tin foil to get them to work properly. With my unit out of warranty I can just about bet that they will tell me the standard repair charge of $69.95 +shipping will apply and that they would be happy to fix it for me.

 

[k3fs]

This is not a case of faulty parts though.

In this case Uniden started production with the cap and resistor marked on the silk screening of the bard, but did not place the solder pads on the board. This is board V01.010.01 as is see in the picture on page 34. RES# and C1 are labeled with no solder pads. There were other issues with this board, RTC, and dimming display.

Uniden fixed the RTC issues, and display issues with a new board. V01.09.-- Boards with V01.09.00 were seen as early as 2015 production. These boards now has RES# and C1 pads. In all cases we have seen the Res# component (resistor or coil?) has been in stalled and the C1 is missing. A picture of this is shown on page 33. These boards with V01.09.02 were used for the RTC and dimming display swap out.

Now in 2016 production the capacitor is starting to show up on the boards. As is seen in the picture on page 37. Still using board V01.09.02

It looks like Uniden recognized the issue shortly after start of production. I am not sure how to explain the appearance of components that fix the issue, other than that. Why it took even longer to add the capacitor on the boards is unknown. It looks like they had knowledge of the issue, and only took a partial step to fix it. Clearly this could have been resolved back with the start of the repair campaign. Not sure why it wasn't. QC issues? A mistake that got through production?

Uniden is obviously ignoring this issue publicly, but privately has taken steps to fix it. Not good support for their "Flag Ship". I wouldn't count on them to resolve this for you. I am sure they would be happy to take your money to fix it though.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.

 

[Ubbe]

It is highly likely that it is the switching power supply, that raises the battery voltage to a higher level suitable to drive the display, that is the cause of the interference and needs additional filtering.

There where obviously some changes done to solve the dimming display and to proper power the RTC backup battery and that might have included the switching power design, that might have raised the emitted RF levels from the circuitry. If FCC have made tests of the new board and approved them then there's no way to demand any call backs of scanners to be reworked.

/Ubbe

 

[chill30240]

Regardless of how all this happened it is going to cost $79.95 for Uniden to repair it. I can either go that route or foil the battery door. This has taught me a valuable lesson about Uniden "flagship" products.