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

[jonwienke]

One correction: The antenna I used for the testing was a spare Uniden factory duck, not a MD-390 duck.

 

[troymail]

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.

Copper foil makes night and day difference in my environment regardless of antenna.

Regardless of "tweak" (seems to be routine with Uniden scanners), there's an unacknowledged problem with the radio.

 

[jonwienke]

Why don't you duplicate my test and see if installing the battery door has as much effect as shifting the antenna with your scanner?

 

[k3fs]

I had tried the Diamond antenna on my 436 when I first got it, due to the poor reception. Yes, it improved. But still not comparable to the 396XT on any old ducky. The Diamond is certainly one of the best antennas out there, and you would expect some improvement. This was used with the adapter. Almost all of my extra antennas are BNC types. Keep in mind, the diamond is a much bigger antenna. Yes, more of the antenna is away from the noise source. But, it receives more of that noise. Same goes with tuned UHF portable antennas. I was hoping to see some improvement, but likely any gain they had was wiped out by the increase noise they were receiving.

I had noticed early on, that mounting the antenna further from the radio helps significantly. I would use a window clip antenna mount on the car with the duck antenna, just to get some reception. I would use the same window clip antenna mount inside, just to get the antenna away from the radio.

Aluminum seems to be a better fix. The foil we used was thick. Regular aluminum foil did not work so well. The copper took 5 or 6 layers. The copper was pretty thin. The combination, of treated battery door, and using the BNC adapter, makes the 436 pretty comparable to the 396XT as far as reception. There was significant improvement with treated door and Diamond antenna, compared to non treated battery door.

Hook the 436 up to an outside antenna, and it out performs the 396XT on the same antenna.

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.

 

[dcisive]

I had an even more rudimentary test on mine. I used a Radio Shack 800mhz antenna so highly thought of out there by many users. I set it standing up both with and without a dual thick aluminum foiled door against my 536 with it's Diamond D130 Discone antenna. What would seem a unfair test, but I figured it would be a worst case.

I first ran scans in the 120mhz, then 400mhz and 800mhz ranges on both scanner at the same time. The 436 picked up the identical stations at the same time in it's scans, and regardless of having the foil on or off the inside of the battery door made NO difference in it's quieting. In fact the 436 without it's door messed with was dead quiet, just as was the 536 on all the channels it stopped on on all the scans including my favorites channels in the 400mhz range. I have a fairly new one so who knows if this was something they've addressed. I'm also using Panasonic Eneloop Pro's 2450mah batteries. Either way I'm thrilled and won't bother to mess with the battery door. With that antenna on it from RS it picks EVERYTHING up with virtuallly full quieting no static or noise or hissing in the background. Can't say that with several other top antennas I've used with it so far. A nice Comet Tribander and the 881 and 889 Watsons and not even the Radio Shack expandable whip with coil. I'm a happy camper. Couldn't ask for a better performing 436.

 

[jonwienke]

I suspect that there may be unit variation regarding the UHF noise emissions. The test protocol I devised provides a way to quantify the level of noise emission from the battery compartment, and test how it may negatively affect reception. For my unit and antenna configuration, it's pretty much a non-issue. For others, it may be a big deal. If we can quantify the percentage of units that are problematic, and how big of a problem the noise is (how many dB the noise floor rises under the wrong circumstances), it's a lot more likely Uniden will pay attention and fix the problem (if there is a problem) than if there is only anecdotal evidence.

 

[bearcat]

I suspect that there may be unit variation regarding the UHF noise emissions. The test protocol I devised provides a way to quantify the level of noise emission from the battery compartment, and test how it may negatively affect reception. For my unit and antenna configuration, it's pretty much a non-issue. For others, it may be a big deal. If we can quantify the percentage of units that are problematic, and how big of a problem the noise is (how many dB the noise floor rises under the wrong circumstances), it's a lot more likely Uniden will pay attention and fix the problem (if there is a problem) than if there is only anecdotal evidence.

What I found with the battery door (and others in my area), signals that the 436 would not hear at all now came in full quieting. I just checked those same signals with a standard door and your antenna configuration and I cannot hear them. As soon as I attach the shielded door. One that is sprayed with RF/EMI spray. Those signals come back perfectly. Can you find a UHF signal that another radio can hear and the 436 cannot? I would be curious. There are a couple of videos that folks made showing DMR signals appearing and disappearing with/without the battery door. Take a look at them.

This thread should be a Sticky. SysAdmin can you please do this.

 

[jonwienke]

What I found with the battery door (and others in my area), signals that the 436 would not hear at all now came in full quieting. I just checked those same signals with a standard door and your antenna configuration and I cannot hear them. As soon as I attach the shielded door. One that is sprayed with RF/EMI spray. Those signals come back perfectly. Can you find a UHF signal that another radio can hear and the 436 cannot? I would be curious. There are a couple of videos that folks made showing DMR signals appearing and disappearing with/without the battery door.

The tests you describe are not useful. They do not quantify the degree to which the battery compartment interference raises the noise floor received at the antenna. With my methodology, you don't need a signal to quantify how much interference is leaking into the antenna. The SDR display gives you a lot more precise measurement of the noise floor change than a 4-segment S-meter.

Conduct the test as I described, using a SDR dongle, duck antenna, and USB extension cable. If what you describe is accurate, tuning those frequencies without the scanner nearby should show a clear spike on the SDR display. Moving the scanner so the open battery compartment is next to the antenna should raise the noise floor enough to bury the spike in noise.

 

[bearcat]

The tests you describe are not useful. They do not quantify the degree to which the battery compartment interference raises the noise floor received at the antenna. With my methodology, you don't need a signal to quantify how much interference is leaking into the antenna. The SDR display gives you a lot more precise measurement of the noise floor change than a 4-segment S-meter.

Conduct the test as I described, using a SDR dongle, duck antenna, and USB extension cable. If what you describe is accurate, tuning those frequencies without the scanner nearby should show a clear spike on the SDR display. Moving the scanner so the open battery compartment is next to the antenna should raise the noise floor enough to bury the spike in noise.

You probably misunderstood me. My tests were not based on a signal being present either. My original tests were done with the AirSpy Mini SDR that is how I found this in the first place. Using SpectrumSpy I looked at the spectrum from about 100Mhz to 800mhz. The noise is present from about 250Mhz to about 580 Mhz to varying degrees. The shielded door significantly reduced the noise over that range. My comment about a weak signal was related to actual on the air improvement. My point is that raising the antenna a few inches or adding a longer antenna did not allow the weakest of signals to be heard. Removing the door during weak signal reception and the signal goes away. Only the shielded door of adding about a foot of coax to the antenna did the trick.

There is obviously some other answer to this issue but Uniden will not even acknowledge the problem.

 

[bearcat]

I had an even more rudimentary test on mine. I used a Radio Shack 800mhz antenna so highly thought of out there by many users. I set it standing up both with and without a dual thick aluminum foiled door against my 536 with it's Diamond D130 Discone antenna. What would seem a unfair test, but I figured it would be a worst case.

I first ran scans in the 120mhz, then 400mhz and 800mhz ranges on both scanner at the same time. The 436 picked up the identical stations at the same time in it's scans, and regardless of having the foil on or off the inside of the battery door made NO difference in it's quieting. In fact the 436 without it's door messed with was dead quiet, just as was the 536 on all the channels it stopped on on all the scans including my favorites channels in the 400mhz range. I have a fairly new one so who knows if this was something they've addressed. I'm also using Panasonic Eneloop Pro's 2450mah batteries. Either way I'm thrilled and won't bother to mess with the battery door. With that antenna on it from RS it picks EVERYTHING up with virtuallly full quieting no static or noise or hissing in the background. Can't say that with several other top antennas I've used with it so far. A nice Comet Tribander and the 881 and 889 Watsons and not even the Radio Shack expandable whip with coil. I'm a happy camper. Couldn't ask for a better performing 436.

It would be interesting to know your serial no. Which would give us the date of manufacture.

Can you post it?

 

[bearcat]

I had an even more rudimentary test on mine. I used a Radio Shack 800mhz antenna so highly thought of out there by many users. I set it standing up both with and without a dual thick aluminum foiled door against my 536 with it's Diamond D130 Discone antenna. What would seem a unfair test, but I figured it would be a worst case.

I first ran scans in the 120mhz, then 400mhz and 800mhz ranges on both scanner at the same time. The 436 picked up the identical stations at the same time in it's scans, and regardless of having the foil on or off the inside of the battery door made NO difference in it's quieting. In fact the 436 without it's door messed with was dead quiet, just as was the 536 on all the channels it stopped on on all the scans including my favorites channels in the 400mhz range. I have a fairly new one so who knows if this was something they've addressed. I'm also using Panasonic Eneloop Pro's 2450mah batteries. Either way I'm thrilled and won't bother to mess with the battery door. With that antenna on it from RS it picks EVERYTHING up with virtuallly full quieting no static or noise or hissing in the background. Can't say that with several other top antennas I've used with it so far. A nice Comet Tribander and the 881 and 889 Watsons and not even the Radio Shack expandable whip with coil. I'm a happy camper. Couldn't ask for a better performing 436.

Keep in mind we are not talking about noise on your received signal. We are talking about noise that totally blocks signals from being received. The only true test is to use another scanner radio (not a 536 on an outside antenna) Look for weak signals, like maybe the input freq to a repeater. If you do not have another portable scanner then you really cannot truly compare how well yours is working.

The 436 works fine on strong UHF signals, it is the weak ones where the issue comes into play.

 

[Fidgety9996]

I was wondering what is not OK with my edacs configuration and i found this topic.
Compared to scanner with trunktracker III on the same system, group config 436hp seems to loose the system completely although flashing 3/4 strips on the signal meter.

is the problem coming from the battery? no idea. but something is wrong.

Uniden support till now through "ask the question" seems to be very poor so i am very disappointed. this is not cheap scanner.

i dont know if the issue is related and can be cause of any interference but while the backlight is on you can hear very high frequency buzz (sth between 17-20 kHz)

UPDATE:
i just found out in this topic many other users reported hiss around 460MHz - that is exactly where my trunked system is !!! Uniden, check this out!

 

[bearcat]

I was wondering what is not OK with my edacs configuration and i found this topic.
Compared to scanner with trunktracker III on the same system, group config 436hp seems to loose the system completely although flashing 3/4 strips on the signal meter.

is the problem coming from the battery? no idea. but something is wrong.

Uniden support till now through "ask the question" seems to be very poor so i am very disappointed. this is not cheap scanner.

i dont know if the issue is related and can be cause of any interference but while the backlight is on you can hear very high frequency buzz (sth between 17-20 kHz)

UPDATE:
i just found out in this topic many other users reported hiss around 460MHz - that is exactly where my trunked system is !!! Uniden, check this out!

Start reading this thread from page 1. You will probably find the answer to your problem.

 

[Fidgety9996]

Start reading this thread from page 1. You will probably find the answer to your problem.

ive just read whole topic, maybe post it here for others? do you mean that the foil/tape resolves the issues?

 

[bearcat]

ive just read whole topic, maybe post it here for others? do you mean that the foil/tape resolves the issues?

It did on the units that I have tested in my area. It is the only answer we have until Uniden steps up and tells us the real cause of the issue. I have little hope of that happening.

 

[Fidgety9996]

It did on the units that I have tested in my area. It is the only answer we have until Uniden steps up and tells us the real cause of the issue. I have little hope of that happening.

i cant believe Uniden is playing like that. If the keep ignoring it it will be my last uniden device. That is scandal. I just emailed them with link to this topic, let us give them a chance. So much detailed information as in this topic cannot be ignored.

 

[jonwienke]

Keep in mind we are not talking about noise on your received signal. We are talking about noise that totally blocks signals from being received. The only true test is to use another scanner radio (not a 536 on an outside antenna) Look for weak signals, like maybe the input freq to a repeater. If you do not have another portable scanner then you really cannot truly compare how well yours is working.

Comparing two radios with two different antennas in that manner is bad test procedure. There are too many uncontrolled variables to draw any undeniable conclusions.

 

[bearcat]

Comparing two radios with two different antennas in that manner is bad test procedure. There are too many uncontrolled variables to draw any undeniable conclusions.

I never said they had different antennas. I have had the sensitivity of both radios checked and they are both about .2mv on UHF. So you are saying that if i sit my 396XT and my 436 side by side and the 396 is receiving a given freq that the 436 is not hearing. I then apply the shielded door and the 436 starts receiving those same signals. How is that not conclusive? It may not be scientific but it sure proves the point to me.

I can tell you that it makes the all the difference in the world on the performance of the 436.

I would love to know a better solution.

 

[Fidgety9996]

UPDATE
my test shown that touchin ONLY the (-) ONLY for the battery on the bottom solves the problem ...
ideas?

 

[bearcat]

UPDATE
my test shown that touchin ONLY the (-) ONLY for the battery on the bottom solves the problem ...
ideas?

Yes that noise seems to be coming from the negative side of the middle battery or a least that is where you can suppress it. A properly shielded door will do what your finger is doing. Hopefully we will find a better solution someday.