statewide astro trunking

khphighwayman · #1 (**permalink**) 12-01-2007, 04:13 PM

maybe somebody can help me out here. the agency i work for began switching over our statewide radio system, which was conventional non trunked 800 mhz towers, to the astro digital trunking system. there our several different talk groups being used on the system which currently includes about 5 or 6 towers/sites. ive noticed my mobile and portable radios will not catch some of the traffic while scanning other talkgroups i have programmed into my scan lists. if someone is using a talkgroup that my radio is set to scan but that same someone's radio is using another tower/site should my radio be picking that traffic up?, or will it only scane the id's that are being used on that particular site? any other useful info on this new system would be appreciated to! thanks.

stateboy · #2 (**permalink**) 12-01-2007, 09:47 PM

This is the new 800 MHz Kansas statewide trunked ASTRO 25 system, yes? Are you with KHP or DOT?

There was the same problem with the early stages of the VHF Wyoming statewide trunked ASTRO 25 system (Wyolink). I'm sure others can chime in, but I think the scan problems started once the system got past a certain amount of talkgroups and the system wasn't able to "keep up" with the scanning demands. I want to say it was a firmware thing with the site/zone controllers or something...?

There may also be restrictions imposed by the system administrators as to how the scan is setup. Why? Because there are issues when a subscriber unit is outside it's "home" area and has scan enabled on those talkgroups, causing the system to tie up resources as you travel because you have your radio scanning "home" talkgroups on "away" towers. This means if you drove from one end of Kansas to the other, with scan enabled, the system would be transmitting your home talkgroup(s) on any tower(s) your radio affliated with as you passed through...causing a massive waste of system resources.

khphighwayman · #3 (**permalink**) 12-01-2007, 11:06 PM

alrighty. Im with the khp. Have been on the road 6 yrs now. The wierd thing is, im within my home area when im scanning. and I've only got four or five talkgroups programmed into my scan list. A fellow trooper will be in topeka which is about 30 miles from where I'm at. He will be calling me on a car to car talkgroup, which is programmed in my scan list, and my motorola spectra won't catch it on scan. We also attempted to key the mic for a short period before he speaks so that we make sure it gives the radio time to scan over. The thing is he will be on the topeka site, and I will be using the next tower west of topeka. Thats when we seem to have difficulty talking. If we are both on the same tower it is not issue.

RocketNJ · #4 (**permalink**) 12-02-2007, 11:01 AM

That's the beauty of SmartZone.

If all the units on the car-to-car talkgroup are on a different sub system than you, then when you are scanning you will not hear it.

Reason is: The system will only assign a channel for that conversation if a radio is on that talkgroup, not just scanning it. This is done to save channel resources.

ofd8001 · #5 (**permalink**) 12-02-2007, 10:59 PM

There's a pretty good explanation of how a statewide digital trunking system works at the following address: http://www.geocities.com/mn_metroscan/800mhz_FAQ.htm

It's for the Minnesota system.

With the conventional systems, the transmitters put out a lot more radio power. The new systems, like what you have, put out a lot less. So while your compadre was calling you, he was on the Topeka tower, which probably didn't put out enough radio horsepower to where you could hear him. As you stated, when you're both on the same tower, you would.

That's probably somewhat of a blessing, because if all units could hear the car to car talkgroup all across the state, that talkgroup may become congested, in that so many would want to use it at the same time.

I don't know how your system is set-up, but if the affiliations are done in a certain way, you could switch to the Topeka talkgroup while you are in the coverage area for your post/district/troop, and then converse with the Topeka unit.

Places like Indiana and Minnesota do that so when a unit is travelling outside of his post/district/troop, he can remain in contact with the home place. Very similar to roaming on cell phones.

REDave · #6 (**permalink**) 12-03-2007, 10:20 PM

RockNJ's explanation is correct. That is how scanning works on a Smart System or on a Motorola APCO Project 25 System.