Off-channel transmissions on 996 and 396

[af5rn]

On both my 996s and my 396, I occasionally get transmissions coming through on a talkgroup that they are not being transmitted on. For example, I monitor only fire talkgroups. No cops. Yet every now and then, I get cop transmissions coming through on a fire talk group. I hear this happen daily, so it's not a rare occurrence. At least the transmissions ARE from the system I am monitoring, and not another system.

Is anyone else experiencing this? Are the radios mistakenly identifying talkgroups? Is a nearby transmitter simply pushing through another talkgroup forcibly?

I sometimes notice it happening after transmission stops on the talkgroup I am monitoring, but before the repeater has dropped out. I cannot, however, tell if this is how it always happens, or if sometimes it just punches through on the wrong group without that talkgroup being already transmitting. It seems like it is doing both.

 

[slicerwizard]

Is anyone else experiencing this?

Yep.

Are the radios mistakenly identifying talkgroups?

Yep.

Is a nearby transmitter simply pushing through another talkgroup forcibly?

Nope.

I sometimes notice it happening after transmission stops on the talkgroup I am monitoring, but before the repeater has dropped out.

Sometimes, a Motorola 3600 bps system will fail to send the disconnect tone before reassigning a repeater to another talkgroup, or your scanner will fail to detect the disconnect tone. This leads to the tailgating you're describing. System users experience the same problem from time to time.

I cannot, however, tell if this is how it always happens, or if sometimes it just punches through on the wrong group without that talkgroup being already transmitting. It seems like it is doing both.

The scanners mis-decoding OSWs and tuning to PD comms that they think are FD comms is probably the more common occurrence. I see it on my 396 from time to time. Do what you can to reduce the false decoding rate (move the antennas away from your PC's, etc.)

 

[Mike_G_D]

Disconnect Tone

Something to check is that you actually have the end of transmission disconnect tone ignore set off. Unidens will give you the option to use the disconnect tone or ignore it. Something the Radio Shack GRE made Pro-96 didn't have - it didn't use the disconnect tone at all and I would often see what you are describing; it just waited for the carrier to drop and/or the modulation to stop for a set time before going back to the control channel. If someone from another talk group got switched to that voice channel quickly enough after the desired user finished I would hear them talking until they ended or I forced the scanner to scan again manually.

However, the Uniden units give you the option of using the disconnect tone or ignoring it; check over your manual to see how to set that feature. If you have it set to ignore then change the setting and see if that helps.

-Mike

 

[af5rn]

Thanks, guys! I appreciate that information!

Like about half of the features on these radios, I had no idea what the disconnect tone setting did, lol. I'll go double check those!

 

[HenryDavid]

My 996T seems to work fine, but not quite as predicted by the manual.

Motorola Type II, I programmed in only the control channels and TGID. For some reason it seems to have put in OTHER TGs, so I hear animal control and other groups I did not put in.

Also, I haven't quite figured out the QK and Group QK thing yet, though I have read the book many times about it.

 

[af5rn]

HD, most of the time when people report hearing TGs they didn't program, it turns out that they are simply in "ID SEARCH" mode instead of "ID SCAN" mode. You can tell by which ever term is scrolling across your screen while scanning.

ID SCAN is when you are scanning through your programmed, unlocked talkgroups.

ID SEARCH is when you are searching the entire system and capturing any active talkgroup, regardless of whether or not that TG is programmed in.

It is really easy (TOO easy) to accidentally bump into ID SEARCH mode without realising it, so check on that. I would bet that's your problem!

 

[HenryDavid]

Thanks, I think that must be the problem.