Priority scan look back time on Astro Spectra 800 Smartnet

rangerfourever · Post by **rangerfourever** » Fri Nov 10, 2006 5:42 pm

Having trouble at work with Astro Spectras while scanning fire (non priority) missing traffic on primary PD dispatch ( set as priority) can the "look back" time for the priority be set to a shorter duration. This is on a 800 Smartnet system.

thanks guys need to call the M program guy next week to get this fixed if its possible.

jmr061 · Post by **jmr061** » Fri Nov 10, 2006 6:10 pm

Under the conventional scan settings there is a priority scan sample rate setting, 250 ms is the shortest selectable setting.

Jason

RKG · Post by **RKG** » Fri Nov 10, 2006 7:03 pm

Priority scan on a trunked system doesn't work the same way that it does on a conventional radio, i.e., by periodically interrupting the non-priority audio and shifting to the priority channel to test for traffic. Rather, radios capable of priority scan (SmartNet II feature set or better, scan list type set as "Priority Monitor", and priority type set as other than "none") observe a subaudible data stream that scolls the TGIDs of all pending Group Call OSWs, and then immediately shift to the voice channel assigned to the group call of the priority talkgroup upon detecting that one is active.

If you are missing what is supposed to be priority traffic, I suspect:

1) The radio isn't capable of handing trunked priority scan; or

2) The scan list has been defined as type "talkgroup" vs. type "priority monitor"; or

3) Priority type is set at "none" for the scan list in question.

bellersley · Post by **bellersley** » Fri Nov 10, 2006 8:08 pm

Also, is the system capable of priority scan? If it isn't, it won't transmit the low speed data. Also, priority scan only works on odd numbered groups.

Josh · Post by **Josh** » Fri Nov 10, 2006 8:10 pm

bellersley wrote:Also, is the system capable of priority scan? If it isn't, it won't transmit the low speed data. Also, priority scan only works on odd numbered groups.

Not to mention that it doesn't work on Astro IMBE systems either. The radio will listen to the control channel information between transmissions, but not while someone is talking (as the repeater hang-time is the control channel data).

-Josh

rangerfourever · Post by **rangerfourever** » Sat Nov 11, 2006 5:48 am

maybe an example will help.... was listening to a working fire on fire dispatch (non priority) with the only other group enabled in scan was pd dispatch ( priority).... seemed to be missing calls, so I turned my portable on and when FIRE was very busy with lots of traffic the radio was not reverting back to PD dispatch. I of course was hearing all PD traffic on my portable as it was not scanning. The rest of the shift I noticed that if the conversation on fire was very brief, the radio would revert back to PD dispatch..still confused I just had M program these radios last week! thanks guys I have to get this fixed and it looks like I will have to hand the M guy fix for him to do

RKG · Post by **RKG** » Sat Nov 11, 2006 6:22 am

I stand by my diagnosis.

apco25 · Post by **apco25** » Sat Nov 11, 2006 9:28 am

It should be set up this way

Priority Monitor

Priority 1 Selected Channel or Op Select

Priority 2 none or op select

Non Priority Members Op Select

Keep the look-back time short .25 miliseconds.

rangerfourever · Post by **rangerfourever** » Sat Nov 11, 2006 10:27 am

thanks guys I will talk to Motorola Monday and try and get the radios redone before the end of the week

thanks again

RKG · Post by **RKG** » Sat Nov 11, 2006 1:59 pm

I do not believe there is anything akin to "lookback" time for scanning with a trunked system.

However, if you use the type "talkgroup" and then mix talkgroups from different systems, you will run into the problem of the radio listening to one system's control channel and unable to hear OSWs on another system's control channel -- even though the first system has no traffic. There is a setting for how long a radio sits on a quiet control channel, but this has no application when scan type is set to "priority monitor," which limits you (properly) to talkgroups from a single system.

A properly programmed SN II or higher radio set for scan type "priority monitor" will continuously monitor the sub-audible data stream WHILE it is listening to the non-priority voice, and it will jump to the priority TG the instant it sees an OSW for a group call on that TG.

rangerfourever · Post by **rangerfourever** » Sat Nov 11, 2006 6:10 pm

I meant HANG TIME, not look-back or sample rate timing for the scan. This is a single Smartnet II system

RKG · Post by **RKG** » Sat Nov 11, 2006 6:36 pm

OK. But in SM II "priority monitor" scan, hang time has no effect on priority calls. It affects only how long a reply on the "current" channel will override traffic on a non-priority channel. Setting this value (which I seem to recall the RSS calls "Rx/Tx Hold Time") for anything less than about 3 sec. means that you will be likely to miss parts of a logical exchange, being interrupted by traffic on some other non-priority scan list TG member. And this value has no effect on the function of the priority scan.

Post by Pj » Sat Nov 11, 2006 11:13 pm

RKG is correct. Everything you know about scanning on conventional systems is thrown right out of the window when it comes to trunked.

Pretty much everything is handled by the radio monitoring the control channel when scanning. If the radio is properly setup for priority monitor AND its enabled on the TRS, then there shouldn't any problem.

rangerfourever · Post by **rangerfourever** » Mon Nov 13, 2006 6:01 am

Ok so if I have this right....the radio must be set to priority monitor scan and the system must be enabled also. I hope the Motorola guy understands this time

Post by Pj » Mon Nov 13, 2006 5:39 pm

Yup.

Radio system has to support it and enabled, radio scan list type must be set to priority scan. Life will be better.

apco25 · Post by **apco25** » Mon Nov 13, 2006 7:45 pm

The system in question DOES support priority scan, its not a system problem.