BCD436HP/BCD536HP: Missing transmission frustration

[majoco]

Why have you got the AGC off? The signal strength meter and the squelch rely on the AGC voltage to work - well, in my radios they do.

 

[jonwienke]

Why have you got the AGC off? The signal strength meter and the squelch rely on the AGC voltage to work - well, in my radios they do.

The AGC setting refers to audio, not RF.

 

[AxelsHumanDad]

There's no need unless the scanner was made several years ago. Uniden made a hardware revision to the 436 several years ago that eliminated this issue.

RFI from the USB power supply is a possibility though.

I just ordered a roll of copper foil from Amazon, it's a cheap thing to try.
Currently have the 436 off USB power, standing in the middle of the desk.
Local channel is generally pretty quiet, so I'm waiting for some chatter...

 

[AxelsHumanDad]

Why have you got the AGC off? The signal strength meter and the squelch rely on the AGC voltage to work - well, in my radios they do.

And off or on made no difference in the issue.

 

[Ubbe]

It's a conventional system, no control channel.

Then it's so much easier to test and hopefully find what is causing the delay. Check that the frequency are set to digital only and set squelch to 0. Look at the signal strenght indicator while you are receiving conversations with both scanners to see if the 436 drops the signal.

If it works now it means that you could have battery save on or some kind of priority function. If you have interference from the logic board you should have that at all times, not only a brief time now and then when holding on to a single frequency.

/Ubbe

 

[AxelsHumanDad]

Just throwing this out there, as this was an issue on the 436, EMI/RFI leakage in the area of the rear battery door. Have you done this mod? An owner mentions attenuation at 155 mhz as a result of no shielding causing lack of reception on a P25 control channel. I would be interested to know if you have done this?

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

This is all done in a portable configuration no external antennas. I probed the case of the 436 and found an excessive amount of noise coming from the bottom rear of the radio. I am not an engineer so I have no idea what kind of noise it is. I applied some RF shielding tape to the inside of...

forums.radioreference.com

After reading the first 20 pages of that thread and doing some tinkering, it "appears" to be from either/or/and:

Noise from the battery compartment (I have copper foil tape coming tomorrow).

Noise from the USB line (I have an upgraded USB cable and ferrite beads coming tomorrow).

The cheesy way I have the outside antenna coax connected-
coax=====> F connector > F to BNC adapter > BNC to SMA adapter > scanner (I have F to SMA adapters coming tomorrow, and compression BNC cable ends coming Saturday).

Another possible noise point could be the USB powered amplified speaker plugged into the headphone jack.
An additional thought is it's just a noisy environment here with multiple LCD monitors and LED lamps.

It was aggravating because it only affects the local sheriff channel. Running the scanner on batteries with the stock antenna sitting in a different spot on the desk "seems" to make the problem go away. I have the USB and audio cables draped in a different direction for now, and I'm running it without batteries installed. Is it 100% resolved? It's noticeably better than it was. A noticeable enough difference in that I went ahead and ordered the 536HP I was hesitant to buy. I was concerned I'd have the same problem with a 536, but apparently there are a lot of details I can work with to avoid the issue.

One other thought, the local system has issues. All too often they call "Unit transmitting unable to copy" or "10-9 you were unreadable".
Way too often...
If a professional public safety system isn't 100% all the time, I shouldn't expect perfection from a mass produced consumer device

Thanks for all the suggestions and help.

Mike

 

[jonwienke]

Unless your scanner was manufactured in 2016 or earlier, don't waste your time worrying about the battery compartment RFI. It was fixed with a hardware change around then.