Losing P25 control channel at end of every transmission

[JBrownCS]

I am using a BCD536HP to monitor the Oakland P25 system and am experiencing a problem where I lose the control channel for a few seconds at end of every transmission which keeps me from hearing any replies or following a conversation.

Is there any I can force my BCD536HP to keep it's lock on the control channel at the end of a transmission?

Holding on a talgroup does not help and I am only monitoring one site in the system. I have my P25 threshold set to 7 man and getting a decode rate of under 45 most of the time. My antenna is a 700mhz Wilson yagi.

I can monitor other P25 systems, EBRCS NW for example, and not run into this problem.

 

[Voyager]

Are you SURE you are losing the control channel and you're not simply seeing the S-meter drop as the scanner scans the system(s)?

 

[JBrownCS]

Voyager - Yes, the DAT icon goes off and then a couple of seconds later it comes back on. If there is a reply I miss the beginning.

My WS1080 doesn't do this but the decode and simulcast distortion is much worse.

My BCD536HP does great when monitoring Emeryville and Berkeley which are in the same area.

 

[fmulder13]

I am experiencing the same problem with my 436hp on the Maine State Communications Network (MSCommNet) Trunking System, Statewide, Maine - Scanner Frequencies system. I have started a thread with this problem, (http://forums.radioreference.com/un.../318072-failing-receive-vhf-trunk-system.html). (The thread started under different pretenses, but my problem morphed into yours.) Please let me know if you find a solution, and I will do the same. It sounds as though we're experiencing the same issue.

 

[Voyager]

Voyager - Yes, the DAT icon goes off and then a couple of seconds later it comes back on.

That is consistent with normal scanning. (not the couple seconds if you are only scanning that one system which should only take a couple hundred mS)

 

[JBrownCS]

I am experiencing the same problem with my 436hp on the Maine State Communications Network (MSCommNet) Trunking System, Statewide, Maine - Scanner Frequencies system. I have started a thread with this problem, (http://forums.radioreference.com/un.../318072-failing-receive-vhf-trunk-system.html). (The thread started under different pretenses, but my problem morphed into yours.) Please let me know if you find a solution, and I will do the same. It sounds as though we're experiencing the same issue.

Solution for me has been to use op25 which has completely solved the dropped control channel and simulcast distortion issues I was experiencing.

 

[troymail]

I believe it is normal to see the signal bars and possibly even the DAT symbol to blink off for very brief periods (I've heard it said this is "housekeeping" cycle). Having said that, if this "off" period is for extended periods - particularly if you are holding on a specific talkgroup - it may be because the radio has lost sync on the control channel (pretty normal for simulcast systems) and is cycling through the programmed frequencies trying to reacquire it. This can take several seconds depending upon how many frequencies are programmed for that system/site.

One thing you can try to see if it makes a difference (other than a different antenna or just moving the radio to a different location) is to do some custom programming where the system/site is only told about and to check the sole frequency that is the control channel (i.e. even if the system/site lists 15 frequencies, only program 1 - the control channel frequency). This can allow the radio to more rapidly reacquire the control channel since it has to go directly back to that frequency since it's the only one programmed.

The downside to this is that if/when the system/site changes control channel frequencies, you'll hear nothing. Still, it's worth experimenting. Many times systems have a primary and alternate CC - you could just program only those 2 frequencies -- it's still faster to reacquire on 2 than it is to reacquire looking through 15....

 

[WA0CBW]

Troymail is correct. The scanner didn't lose the control channel it just didn't re-aquire it after the end of the conversation. The scanner only listens to the control channel when there is no talk group activity. When a talk group is assigned a voice channel the scanner drops the control channel and goes to the voice channel. When the voice channel ends the conversation the scanner goes back to the control channel. It would appear that the scanner is having a hard time locking onto or finding the control channel. Try troymail's suggestions.
BB

 

[JBrownCS]

I did try a custom favorites list that had only the control channels for the system I was monitoring but that did not solve the issue.

The other question is why does this only occur when I monitor the Oakland P25 system? Other P25 systems that are a similar distance from me do not exhibit this behavior.

 

[ofd8001]

When you are receiving voice transmissions, are they pretty clear - no garble or "going digital"? If they are not clear, I'd be wondering if you are right at the very edge of coverage. (Notihg the comment of other P25 systems at similar distance, but perhaps not of similar power output).

 

[jim202]

When you are receiving voice transmissions, are they pretty clear - no garble or "going digital"? If they are not clear, I'd be wondering if you are right at the very edge of coverage. (Notihg the comment of other P25 systems at similar distance, but perhaps not of similar power output).

Not knowing how Oakland is set up to trunk, is it possible that that system doesn't use the same voice channel for the next person on the same talkgroup and does a new voice channel assignment with each transmission? This will mess up some scanners. It also is not the norm for how systems are normally set up to function as it adds more overhead traffic to the control channel.