Actually, I'm finding it greatly reduced (if there at all) with no batteries in the unit - particularly when you remove that middle cell. That makes sense sicne you're removing the unintended antenna (that middle cell).
BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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Actually, I'm finding it greatly reduced (if there at all) with no batteries in the unit - particularly when you remove that middle cell. That makes sense sicne you're removing the unintended antenna (that middle cell).
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darunimal
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darunimal
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When did I say anything about IFX, step and modulation can make a hugh diffference if it can or can't be seen.
Rich is N9JIG, Voyager is______, since we are on a first name basis
When did the design change for anything but the literal RTC or LED components
Rich is N9JIG, Voyager is______, since we are on a first name basis
When did the design change for anything but the literal RTC or LED components
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darunimal
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I also said in post 11 in this thread that "it was a known to improve UHF reception" to use an external antenna.
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darunimal
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OK. I consider it "gone" when it no longer affects reception. But I see your side of it, too. It's still there - just not to the extent it makes a difference.
To put some context to this, I see about a 25 dB noise floor increase with the cells in, and less than a 10 dB increase with them out. This 10 dB increase is not strong enough to make it to the antenna (or very little of it), so the affect on performance is not nearly as dramatic.
With them out, I also see the source best in the area of the SD card. I removed the card and the noise is still there (at the reduced level).
Now, with the non-affected unit, the same test yields a maybe 3 dB increase right on the SD card, and that could be attributed to capacitive coupling simply making a better antenna on the probe. I see no increase at all anywhere else in the battery compartment - as in 0 dB.
I still would love to see a cap to ground from the one side of the center battery, as I believe that may be the most effective mod. But I do not have the tools to do that handy.
Read what I said. I said he tried to shield the entire rear.
You didn't. I conducted the tests you suggested and additional similar tests. I am not limited to only the tests you propose. I will try anything I can to find the cause. I also did not criticize your suggestions or dismiss them even though I was skeptical of at least one of them.
Eye on the ball - let's try to find the solution rather then find faults with posts.
Joe if you must know. Not that it matters, and you've come up with some creative names before. :wink:
BTW Rich is Bearcat in the context I've been using.
I don't know. But I also don't know that it didn't change. If you are saying for a fact the design never changed, I would be suspect of that, but I'll let you make that statement first. I'm certainly not going to assume it is identical - especially based on the fact we know the LEDs changed, so some supporting components may have had to change as well. Ditto with the clock.
So test that theory.
It's odd that I'm not seeing the strongest signal in that area, but by all means test away. And please don't limit yourself to anything I suggest. If you can think of a test, by all means feel free to perform it. I really don't care who finds the cause as long as it's found and confirmed.
I did not do that. I just put shielding tape on the inside of the plastic rear case. Are you going to try covering that shield plate? Go for it.
Some may not see it if every UHF signal in their area is stronger than the noise being injected to the antenna. As I said in the beginning, this is not so much about what you are hearing but what you are not hearing. I can remove the door and lose a signal totally or on low signals removing the door introduces tons of noise on the audio. On full quieting signals I really cannot tell there is any noise problem going on. Do the door ON/OFF test. Tune to the new DMR freq you found. Remove the door while they are talking. See what happens. If the signal drops out, it is working.
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darunimal
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Do you see the yellow box in 2 pictures. See previous post.
Yes I see that in your photo. Are you or did you try to shield that area? I did not. I just shielded the plastic rear case.
My model is a Z5, so I guess 2015? It showed improvement with the fix. I have 3 layers of copper foil tape on the back door. It is a nice, snug fit. : - )
Correct.
Air Spy Probe with Spectrum Spy
I performed a probe of my 436 using AirSpy2 and Spectrum Spy and stubby antenna on the Airspy. I know this is not a calibrated measurement device but here is what I found. I had a center freq of 460.000 and 200mhz scale.
Shielded Door Off:
I had about 30db of noise at 350 Mhz which diminished to about 20db around 410Mhz thru 480mhz. Starting at 480Mhz the noise appears to diminish to maybe 5db or so up 550mhz.
Shielded Door On
There was still about 15db of noise a 350Mhz which diminished to maybe 5db at about 410mhz and stayed at 5db up to 500mhz.
Hence more shielding somewhere should help. We just need to figure out where.
I performed a probe of my 436 using AirSpy2 and Spectrum Spy and stubby antenna on the Airspy. I know this is not a calibrated measurement device but here is what I found. I had a center freq of 460.000 and 200mhz scale.
Shielded Door Off:
I had about 30db of noise at 350 Mhz which diminished to about 20db around 410Mhz thru 480mhz. Starting at 480Mhz the noise appears to diminish to maybe 5db or so up 550mhz.
Shielded Door On
There was still about 15db of noise a 350Mhz which diminished to maybe 5db at about 410mhz and stayed at 5db up to 500mhz.
Hence more shielding somewhere should help. We just need to figure out where.
I ordered EMI Shielding conductive tape from Amazon and applied it on Friday night. The difference is night and day. My BCD436HP went from taking approximately 0.5 seconds per DMR channel to about 5-7 channels or more per second during scan. It used to take several seconds to cycle through a list of DMR sites in a Connect+ system -- now it scans it all ridiculously fast. I believe that instead of comparing signal strength before and after the tape, it may be a better test to see how long the radio sits on quiet channels instead -- if the signal strength of distant stations doesn't change, but we lowered the noise floor by applying the tape, it seems to be much more selective of what it sits waiting on now. It doesn't get delayed checking every channel so long because of the noise. Here's the tape I ordered: Tapes Master 10ft Copper Foil Tape - EMI Shielding Conductive Adhesive (1/2" Wide)
troymail
Silent Key
We're gathering more clues --
* when did you purchase your radio?
* what is the serial number (digits apparently indicate manufacture date)?
* has you unit been in for any repairs (LEDs, battery, other)?
I purchased it in March, 2014 and the serial is 376Z48000xxx. It's only been serviced by Uniden for the RTC repair. Also, I applied the tape over the foam.
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troymail
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