BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
- Start date
- Status
Here is what I did today with a aluminum foil battery door test. I just ordered the copper tape.
https://www.youtube.com/watch?v=qv4TlWZXAS8
https://www.youtube.com/watch?v=qv4TlWZXAS8
Last edited:
Excellent video. Exactly the results I am seeing here.
Weeks ago I seen 1-2 bars for signal nothing was happening. When I put this test on those 1-2 bars aren't showing up. I wonder cause of the clouds was helping the signal today I'll try tomorrow if no clouds are around. The tape should be here Thurs if so I'll try to do some tests Fri before work. I just check the AFB Trunking P25 system I get 2 bars with DAT showing on the screen
Last edited:
ptburton11
Member
- Joined
- May 20, 2013
- Messages
- 6
I tried this fix on the inside of the battery door with copper stick-on tape. It made a very significant difference in the hiss/noise while using a duckie antenna. Thanks a million for this suggestion.
Paul Burton
Paul Burton
jeffm77
Member
Would be cool to see more videos of a before and after. I'll have my copper tape tomorrow. I got the EMI reducing tape off Amazon.com. was 9.95 I believe.
Using the serial command of "PWR" to get the RSSI level you can see the noise floor difference with and without the lined battery door.
With- 122
Without- 199
No antenna- 67
Receiving a signal at 3 "bars"- 313
This was at 450 MHz, your levels may (actually will) vary depending on local noise, your antenna, level of battery door attenuation, etc..
With- 122
Without- 199
No antenna- 67
Receiving a signal at 3 "bars"- 313
This was at 450 MHz, your levels may (actually will) vary depending on local noise, your antenna, level of battery door attenuation, etc..
I am overly joyed that the radio is now on a level that I expected when I bought it. I hope we can continue to tweak this and find a way to eliminate all of the noise. I think we are close.
Are those first two numbers correct? Or am I reading it incorrectly? The way I interpret that, you are getting the strongest signal (highest RSSI value) when receiving a signal at 3 bars... then the next strongest signal is without the shielded battery door installed, and with the shielded door installed, you get a weaker signal than that?
I don't have any tape yet, but I will do the SDR stick test in a minute here with my radio.
Yep, they are correct. This shows the level of noise being generated from the battery area.
The first 2 are not receiving any signal, maybe that was confusing you.
Now I am confused. Are they showing an adverse effect by using the shielded cover?
No, the higher the number the higher the signal level or noise floor in this case.
So 122 with the cover is less noise floor than the 199 without the cover.
I guess I could use an iso-tee and measure the desense...but it's just a scanner.
Ok, I think I understand now. The RSSI test, I think, won't be useful for me since I don't have a shielded battery door at this point.
But here are my tests with SDR#. Read into this whatever you wish:
1. Baseline: 436 not turned on, not plugged in, a distance away from the SDR stick (which has on it the metal back-of-set antenna that comes with the 536, via an MCX-to-BNC pigtail). SDR# tuned to 460.000.
2. 436 turned on, not tuned to any particular frequency (in Quick Search mode in 406-470 range). SDR stick with antenna placed lengthwise along the center battery of the radio (with battery compartment cover off). Just placing the tip of the antenna against the battery had no effect; this shot was taken with the BNC connector of the antenna right against the battery. SDR# tuned to 460.000.
3. 436 turned on, tuned to 461.850 in Analyze/RF Power Plot mode, receiving decent signal from a DMR Tier 3 control channel (2 bars, RSSI 247 by PWR command). Battery door (with no shielding) still off the back of the radio, SDR stick and antenna approximately 1 foot away. SDR# is tuned slightly down from 461.850 (461.850 is approximately 1/2 grid box to the left of the spike that is visible roughly 2 grid boxes to the right of the tuning indicator; you'll see where 461.85 is in the next pic).
4. 436 turned on, tuned to 461.850 in Analyze/RF Power Plot mode, receiving decent signal from a DMR Tier 3 control channel (ran out of hands and could not issue PWR command, take the screen shot, and hold the SDR# antenna to the radio all at once, but the radio still showed 2 bars). SDR stick and antenna laid parallel to center battery, in same fashion as in pic/step 2 (BNC touching battery). Note that the signal of 461.850 appears on the SDR# display now, showing roughly -15dB. (With SDR# tuned to 461.850, in step 3 the signal was inaudible, but in step 4 it improved enough to be detectable to the ear.)
All tests were done with a Diamond SRH-789 metal telescoping antenna on the 436, and fresh eneloop XX batteries installed.
Last edited:
I'm sure someone will ask...
RSSI of 122 is ~116.8 dBm
RSSI of 199 is ~107.5 dBm
So it appears about 10 dB worth of noise is making its way to my antenna.
Are you using aluminum tape? Because I am seeing about 8 - 10 db of noise with the aluminum tape that is still leaking through. It was 20 db without the tape. So 10 db of noise make sense. Hopefully we can eliminate that last 10 db with more testing.
I'm not familiar with the metrics available on the radio, but if RSSI is the only option, for the results to be meaningful, the measurement should be taken several times and on several different frequencies. Ideally this would be done on peaks identified.
One measurement on one random place of "noise" isn't a very complete picture. Heck someone could be transmitting on that frequency for all you know.
A better metric would be Signal to Noise ratio. Is that not available? Surely the signal bars measure SNR not RSSI.
Even better would be to get a snap shot through the discriminator out or use a SDR dongle with the radio antenna where it would normally be. Getting an idea of the noise floor like in Jay's test is ideal. For instance, there is a relative peak in the left of his second image. Doing RSSI there versus 1 megahertz up would give completely different results.
Check out something like RTL Dongle Panorama for an better idea of the RF environment.
One measurement on one random place of "noise" isn't a very complete picture. Heck someone could be transmitting on that frequency for all you know.
A better metric would be Signal to Noise ratio. Is that not available? Surely the signal bars measure SNR not RSSI.
Even better would be to get a snap shot through the discriminator out or use a SDR dongle with the radio antenna where it would normally be. Getting an idea of the noise floor like in Jay's test is ideal. For instance, there is a relative peak in the left of his second image. Doing RSSI there versus 1 megahertz up would give completely different results.
Check out something like RTL Dongle Panorama for an better idea of the RF environment.
I also ordered some copper tape and tried some aluminum foil tonight in the meantime until the tape comes in the mail. Sure enough, even some foil made a difference in hearing UHF signals. In one case, I couldn't hear a nearby county's P25 control channel at all beforehand, but as soon as I shielded the battery door with foil, I could hear the control channel and was even able to scan the system.
I'm curious how difficult it would be for Uniden to make shielded battery covers and start a replacement program like the repair campaign for the real time clock issue. Seems like this kind of thing should have been incorporated into the radios in the first place and we really shouldn't have to be all going out and buying tape, fixing our own battery doors, etc. In my opinion, we should be able to submit our scanner info to Uniden and have them mail us a new shielded battery door.
I'm curious how difficult it would be for Uniden to make shielded battery covers and start a replacement program like the repair campaign for the real time clock issue. Seems like this kind of thing should have been incorporated into the radios in the first place and we really shouldn't have to be all going out and buying tape, fixing our own battery doors, etc. In my opinion, we should be able to submit our scanner info to Uniden and have them mail us a new shielded battery door.
- Status
Similar threads
