P25

Jim1348 · Post by **Jim1348** » Wed Aug 23, 2006 8:26 pm

I am still coming up to speed on P25 conventional systems. As I understand it, P25 conventional systems need to have a NAC code programmed and are also capable of talkgroups. What I don't understand is if these are similar to community repeaters on analog. For example, if you have a Motorola Quantar and have a single repeater pair, could you simply set it up for multiple NAC codes rather than a single NAC code and multiple talk-goups, or is there something else that I am missing here? I assume that any way you slice it it is only capable of handling one conversation at a time. Or is that not correct either?

Bruce1807 · Post by **Bruce1807** » Thu Aug 24, 2006 2:40 am

You have a fair understanding.
Treat the talkgroups as PL although a whole lot better.
Yes FDMA only supports one time slot.

The new stuf comming out will be FDMA/TDMA.
The TDMA supports two timeslots but may go to four like Tetra

judoka · Post by **judoka** » Thu Aug 24, 2006 2:58 pm

The NAC is the repeater selection part of PL ie changing the transmitted NAC or the received NAC programming in the terminal should be used to select which repeater on a given frequency you want to hit or listen to.

Repeaters don't care about talk groups, they can only be configured for NACs

The Talk Group is the terminal squelch selection part of PL, ie changing the transmitted talk group changes which bunch of people you are talking to.

Terminals can be programmed to listen unsquelch on anything digital, a specific NAC or a combination of NAC and Talkgroup.

You can use the NAC exactly like PL to do both jobs but it isn't as flexible and not using P25 how it is supposed to work.

Jim1348 · Post by **Jim1348** » Sat Aug 26, 2006 7:18 am

Thank you very much for the reply. Also, is there such a thing as split NAC codes? For example, is it possible to have a transmit NAC of 29E and a receive NAC of 68F on a repeater?

Dale Earnhardt · Post by **Dale Earnhardt** » Sat Aug 26, 2006 10:54 am

Yes that is possible for having two diffrent NAC codes.

If I remember right and if the othe guys can correct me but if I remember right if you set the repeater up for Mixed Mode then you can only have 1 Set of Reagular PL for the Analong side and 1 Set of of NAC for the Digital side. meaning they have to be the same...... and if you were to just have it pure digitial then you can set it to have diffrent NAC ID for TX and RX...

It's been awhile... I think the guys with the quantar can tell you. I might be off lol.