Priority scanning

[ofd8001]

Is there any reason why using DND Priority Scan Mode would cause Priority ID Scan to not work?

Here is the scenario: Priority Scan Mode is on with a 2 second interval. I was holding on a non-priority talkgroup in a P25 800 system that was inactive (no transmissions). A Priority talkgroup in the system became active, but the scanner did not go to the active priority talkgroup. (I had another radio going so I knew which talkgroups were and were not active.) However a priority conventional frequency became active and the scanner jumped to it just fine.

The only thing I can think of is that the DND Priority Scan Mode is "superseding" the Priority ID Scan function. Perhaps jumping off the trunked system every 2 seconds to check the conventional frequency isn't giving the scanner enough time to check the control channel for priority talkgroups.

 

[Ubbe]

Trunked p25 have "late entry" that it continuosly sends the active talkgroups on the control channel.
Only scenario when you don't receive the priority TG are when you are on a control channel that have no radios affiliated to it with that TG and your other scanner are on another sites control channel.

/Ubbe

 

[ofd8001]

This is a real big system with a couple of thousand subscriber units. The two talkgroups I was mentioning are primary police and fire. Fire stations have base stations always on, so there will always be some fire units affiliated to the site. I also confident there will always be numerous police radios affiliated with the site on PD talkgroup.

 

[SOFA_KING]

ofd8001,

I suspect your theory of operation is correct. Since I discovered how incredibly useful Priority DND is for conventional scanning, I also noticed it behaves the same on trunked systems. It will wait for a non-priority channel to finish before switching to a priority channel. But I do see it putting preference on TRS priority channels over non-priority channels. It would be nice to have a system-wide choice of the type of priority you want to use. Maybe on the next line of scanners...

I use a 1 second priority sample interval on Priority DND, and it's super fast getting the important channels locked in. I'm really amazed at how much action I now hear that I didn't before trying this. For areas that use a lot of conventional, this is like having a hyper-speed boost. But I don't feel like non-priority channels are left behind. I still get a good amount of secondary traffic. The key to giving them enough "air time" is setting scan delay long enough to get the replies. I find 5 seconds works well here, but some Connect Plus networks hold longer, so I dial those down to 3 or 2 seconds.

If you really spend the time to tweak all the parameters (priorities, delays, bandwidth [FM/NFM], volume levels, squelch codes, rectangular lat/lon, department control(s), garbage channel avoids ...), you can make one of these scanners work as well (or better) than the actual pro radios you are listening to. They don't scan hundreds of channels like we do, so utilizing these advanced features makes a huge difference. When done right, it's a far cry from scanning the default RR Database like an HP-X. In fact, The HP series has no priority at all, no NFM filtering, and only circular lat/lon with too much overlap to be useful on tall or wide boundaries. The advanced features of the x36 line pay off if you utilize them.

Phil

 

[Ubbe]

DND means Do Not Disturb ongoing calls. It will only do priority scan when current channel is idle.
I believe we all understand that.

Worst case is 360mS between transmission on the P25 control channel info about ongoing Talk Goups.
With a 2sec check time for analog DND priority it receive 5 frames with the TG info and take away 1 or 2 frames for any syncronisation problem that migh occure.
The scanner doesn't do anything different than normal until that 2 sec timer kicks in to check for analog channel action.
It must be something else going on, maybe one of the analog DND prio channels made it "stick" to it for some reason.
Perhaps the signal was just low enough to not open audio squelch but activated signal squelch.
The TG prio scan only works while monitoring it's control channel and for some instances also when monitoring another TG on that site.

/Ubbe

 

[SOFA_KING]

If we all understand that, why point it out?

All Priority DND does is make your priority channels a separate scan list that scans after active transmissions end and again at the time interval set between normal scanning. On trunked systems it seems to give priority channels first shot in the TG list. Not complicated at all. It seems to work well at pushing important channels up front (and scans them more often on conventional channels) without punching holes or interrupting active transmissions. In essence, two level scanning. The order of channels in the priority list matters, and are prioritized from top to bottom, so make sure your most important channels are on top. Fire Dispatch is on the very top of my list, and it does override priorities lower down the list as soon as their transmissions end. The results are staggering!

Great feature! I wish I tried it sooner.

Phil