I offered one, post #578 in this thread. It is a method for quantifying exactly how much self-interference your scanner is generating at a given frequency range, and how much that interference is raising the noise floor at with a given antenna configuration.
BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
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I offered one, post #578 in this thread. It is a method for quantifying exactly how much self-interference your scanner is generating at a given frequency range, and how much that interference is raising the noise floor at with a given antenna configuration.
Fidgety9996
Member
i was actually touching - of bottom battery not the middle one. In my case that seemed to give better results.
seth21w
Member
Hmm i will have to get my buddy to make me a battery door with a solid piece of copper on his lathe, that should do the trick!
Don't contact more than one battery terminal with foil, or you will be shorting batteries out.
Actually the foil should not touch any of the terminals.
Yes I read it but it does not improve my unit. Adding the adapters is really nothing more than increasing the length of the antenna. I'm glad it worked for you.
I am not sure but did your test show the door only reducing the noise floor by 1db or did I read it wrong?
SOFA_KING
Member
Why are we going to all these "lengths" to reduce radiated noise?
Wouldn't the best thing be to use a bypass capacitor to squash the radiating noise before it exits the scanner?
If I still had access to a spectrum analyzer, I would use a sniffer loop to localize the noise. Then try some capacitors in different parts of the circuits in that area to filter off the noise. That is how it's done in the industry. I would be doing that IF I still had an analyzer. Of course, a schematic diagram of the UUT would help a lot.
Phil
Wouldn't the best thing be to use a bypass capacitor to squash the radiating noise before it exits the scanner?
If I still had access to a spectrum analyzer, I would use a sniffer loop to localize the noise. Then try some capacitors in different parts of the circuits in that area to filter off the noise. That is how it's done in the industry. I would be doing that IF I still had an analyzer. Of course, a schematic diagram of the UUT would help a lot.
Phil
That would be great. We just need the person with the knowledge and ability to find the offending part or missing part. In previous posts some have tried to fix it with a CAP but I guess they never found the right place to put it. I agree that is going to be the fix.
The door on or off only made 1-2dB of difference with my scanner. Raising the antenna made about 4dB difference. I use the Diamond RH77CA with the BNC connector because I switch between base, mobile, and handheld use frequently and it's faster to switch if everything has BNC connectors.
Run my test with your scanner, and post your results. It's the only way to quantify the degree of self-interference, and figure out if the issue is the same for all units, or is a only problem for only a few units, or only affects a certain serial number range. If what you're describing is accurate, the battery door should make more of a difference than it did for me.
Run my test with your scanner, and post your results. It's the only way to quantify the degree of self-interference, and figure out if the issue is the same for all units, or is a only problem for only a few units, or only affects a certain serial number range. If what you're describing is accurate, the battery door should make more of a difference than it did for me.
You can't fix the problem with a bypass capacitor if the source of the noise is the clock for the scanner CPU, or the memory bus lines, etc. Putting capacitors on those would prevent the digital components from working properly. One of the biggest engineering challenges for getting high-speed digital stuff to work reliably is to reduce capacitance on the clock and data lines. Increasing capacitance increases crosstalk between lines, and increases power consumption, which increases chip heating, which has all sorts of bad effects.
I cannot try it until later today, but my battery door reduces the noise about 13db. When I tested last night the noise measured at the battery door is about 18db above the noise floor. With a door sprayed with RF/EMI and the foam covered with a strip of aluminum shielding I only see noise about 4 or 5 db above the noise floor. Also with the door installed the noise in the area of the antenna is maybe 1 or 2 db above the floor.
We have already done the serial number study earlier in this post and there is no correlation between SNs and the noise.
When I started this last July, I was able to get my hands on about 25 units locally and they all had the problem. With SNs from the years 2013 - 2015
Let's not make assumptions about where this noise is being generated until it is proven. Many have stated that the batteries are acting as an antenna for the noise. If you run the radio on USB power without batteries installed the noise is not an issue.
So let us have facts before we count anything out.
troymail
Silent Key
That fact that Uniden doesn't even acknowledge the problem and forces their customers to call it out and try to debug and solve it for them speaks volumes.
Do mean attaching the SDR to the Antenna Jack? If so I see only about 1db (if that) increase.
I not sure what you mean by mounted to the scanner position.
Amen!
Fidgety9996
Member
Everyone that has these problems please report it to uniden through this URL after registering:
Customer Support
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Here's some photos of my test setup:
The first shows how I set the noise floor, SDR clamped to a wood table, no electronic devices nearby.
The second shows the stock antenna positioned to closely approximate being connected directly to the SMA connector on the scanner.
The third photo shows the change in the noise floor, approximately +3dB.
The fourth photo shows the Diamond antenna positioned as-connected to the BNC adapter.
The fifth photo shows the resulting noise floor change--less than 1dB.
The dotted yellow line on-screen shows the reference noise level--nothing near the antenna. The reference noise level is slightly higher with the Diamond antenna than the stock duck.
The first shows how I set the noise floor, SDR clamped to a wood table, no electronic devices nearby.
The second shows the stock antenna positioned to closely approximate being connected directly to the SMA connector on the scanner.
The third photo shows the change in the noise floor, approximately +3dB.
The fourth photo shows the Diamond antenna positioned as-connected to the BNC adapter.
The fifth photo shows the resulting noise floor change--less than 1dB.
The dotted yellow line on-screen shows the reference noise level--nothing near the antenna. The reference noise level is slightly higher with the Diamond antenna than the stock duck.
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Using your setup I see about the same figures. Once I apply the shielded door there is no change at all in the noise floor.
Here are my tests using the SDR as a sniffer.
Standard Battery door no shielding:
At middle battery negative side 22db increase in noise floor
At antenna base 5 db increase in noise floor
At tip of antenna 3 db increase in noise floor
RF/EMI Sprayed Door installed
At middle battery negative side 4-5 db increase in noise floor
At antenna base maybe 1 db increase in noise floor
At tip of antenna no change in noise floor
Here are my tests using the SDR as a sniffer.
Standard Battery door no shielding:
At middle battery negative side 22db increase in noise floor
At antenna base 5 db increase in noise floor
At tip of antenna 3 db increase in noise floor
RF/EMI Sprayed Door installed
At middle battery negative side 4-5 db increase in noise floor
At antenna base maybe 1 db increase in noise floor
At tip of antenna no change in noise floor
I will do it, but do not be too encouraged. This thread was started 8 months ago and they have not do anything so far.
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