BCD436HP/BCD536HP: BCD436HP Gets Stuck on Specific Site Until Physical Contact Made

[StickyBit]

I observed a strange issue the other day while running my Uniden BCD436HP. I noticed after a while of it sitting at my desk that it had become abnormally quiet. When I went to grab the scanner, it almost immediately caught traffic. I started keeping my eye on it, and I noticed a pattern. It would scan until it hit a particular Site named Goshen Peak, then it would get stuck. It would remain stuck indefinitely until I touched the scanner. I was able to repeat this behavior many times, and decided to capture it on video. It's almost 5 minutes long, and not that exciting, but I wanted to show the behavior as it happened. I checked my antenna and it was screwed in firmly, not being loose at all. You'll see me holding my camera near the screen to try and help you see the screen output, and then grab it on occasion to make physical contact and try to get it unstuck from the Goshen Peak site. Don't be freaked out by the awkward way I'm holding it. I had some stitches in, so I was grabbing the detector kind of awkwardly due to this, trying to avoid the wounds in my hand and fingers.

Video: ~5mins, 729 MB
https://www.fullfilez.com/files/BCD436HP_stuck_on_site.mov

 

[Railbender]

Does it do it if you place the scanner in a different location?

 

[StickyBit]

Does it do it if you place the scanner in a different location?

Good question. I'll try moving the scanner around to a few different locations in the building and see what happens.

 

[jonwienke]

Probably RFI, being reduced when you touch the scanner.

 

[tvengr]

Does the scanner display a talkgroup when it gets stuck on the site.

 

[StickyBit]

Does the scanner display a talkgroup when it gets stuck on the site.

It does not. It looks like this endlessly until I touch the antenna, or sometimes grab the device itself.

 

[tvengr]

Do you have all of the frequencies for the system entered or just the control channel and alternates. If they are all entered, delete all frequencies other than the control channel and alternates.

 

[Ubbe]

Strange that it get stuck on that site of the analog moto system until you block the signal by holding your hand over the antenna.
If it doesn't receive an active conversation it should continue to scan other sites after 1,5 sec, or longer if you manually have set the hold time to a non default value.

As mentioned it's probably happening due to interference as the control channel are 851.2500 and those even numbered frequencies are easily interfered. That's why most of the frequencies where I live are offset by 6,25Khz that have a less chance to be interfered from reference crystals and clock signals.
I get lots of intererencies on the VHF marin band that uses even frequencies with 25Khz steps but hardly anyting on our other national frequencies like 172.41875Mhz

Try to set that control channel frequency to IFX.

/Ubbe

 

[MisterLongwire]

Plain and simple RFI. Try moving the radio to another area or even try replacing the antenna with another. regardless of freq you are listening to

 

[StickyBit]

Do you have all of the frequencies for the system entered or just the control channel and alternates. If they are all entered, delete all frequencies other than the control channel and alternates.

I programmed it using the Uniden Sentinel; BCDx36HP Sentinel, making a Favorites list using it.

Opening up my favorites list in ProScan, reveals that the Godiva Peak site is scanning for 5 frequencies:





Therefore it looks like I'm setup to scan the 5 frequencies listed for that site matching the RR database at the moment.

If I understand correctly, 851.250c is the control channel, designated by the small "c" after the frequency, and therefore any frequency listed with an "a" would be an alternate control channel? This site then would only have a single control channel and no alternate, so I should then delete all frequencies in this system except for the 851.250c, is that correct?

try replacing the antenna with another.

This morning I started using a REMTRONIX antenna that the seller provided me with. I don't know the exact model number, so I'll include an image of it here. So far, I'm seeing the same issue using it at the same location, where it will get stuck on the Godiva Peak site. Getting it "unstuck", is more difficult with this new antenna. I can grab the antenna and it won't make a difference. I have to touch the exposed metal part of the coupler for the scanner to move on in the scanning process.

Does it do it if you place the scanner in a different location?

This morning I tried moving the scanner to the other side of my desk, about six feet from where it previously was, but it didn't make a difference. I'll have to try taking my scanner with me to other areas of the building, 50, 100, 200 feet away, and see what happens.

I'm observing that if I lay the scanner horizontally on my desk, it's not getting stuck on Godiva Peak, using this REMTRONIX antenna. Now I'll have to see if the same is true when I use the stock antenna. I should have brought it with me. Another day, another test awaits.

 

[jonwienke]

The problem is NOT the antenna. It's RFI. Track down the source and resolve it. Get a $20 SDR dongle and SDR#.

 

[StickyBit]

The problem is NOT the antenna. It's RFI. Track down the source and resolve it. Get a $20 SDR dongle and SDR#.

I understand what an SDR USB dongle is, but what do you mean by "SDR#" ?

 

[jonwienke]

Software that lets you use the dongle to hear and see radio signals. The band scope display is useful for finding RFI sources. Use a 10-foot USB extension cable so you can move the dongle around like a metal detector to find the source.

 

[ot0tot]

I understand what an SDR USB dongle is, but what do you mean by "SDR#" ?

Get SDR# here: SDR# and Airspy Downloads - airspy.com
I recommend the RTL-SDR blog v3 SDR dongle, available from Amazon.

 

[mikewazowski]

If I understand correctly, 851.250c is the control channel, designated by the small "c" after the frequency, and therefore any frequency listed with an "a" would be an alternate control channel? This site then would only have a single control channel and no alternate, so I should then delete all frequencies in this system except for the 851.250c, is that correct?

Correct. Delete everything but the frequency marked with a "c" and see what it does.

The other thing to do is enter all 5 frequencies in as conventional frequencies and see if one of the frequencies has a silent carrier on it. You should hear a data signal on the frequency marked "c" and possibly voice on the others. No need for anything else.

 

[Ubbe]

You can use the scanner to pinpoint any source of RadioFrequencyInterference. Stop scanning by pushing the CHAN button. Then enter 851.25 and push the CHAN button again. Turn down squelch to zero and listen to the audio while moving the scanner around in the room. The control channel sounds like a chainsaw or something and the interference could sound as anything besides that depending of what type of interference it is.

Enter the other channels as well, by entering the frequency and then CHAN button, and listen. It could be that the control channel decodes that a conversation are taking place and sends the scanner to a voice channel but that could be interfered so that the squelch doesn't open and it goes back to the control channel and starts over again, and it will be stuck on that site.

/Ubbe