What is (APCO-25 NAC 165)

[DOH6713]

This is what is posted on the database for my home town;

158.92500 153.87500 KVJ918 RM Sheriff Operations (APCO-25 NAC 165) APCO-25
(This is exactly what i am looking at; http://www.radioreference.com/apps/db/?ctid=2687 ;This is the link to my home town database)

All the county frequencies that are APCO 25 have this tag with them "APCO-25 NAC 165". I've looked a lil but can't find out what this means. In lamen would i be wasting my $$$ getting the PRO 96 to scan these APCO protected freq's?

[MtnBiker2005]

The Wiki talks about the NAC stuff. It's just like CTCSS tones or DCS tones etc etc.
ALL APCO-25 will have a NAC ###. Even on a P25 Radio system.

http://wiki.radioreference.com/index.php/NAC

[DOH6713]

OK thanks. Now i can go shopping!

[MtnBiker2005]

but IF you want to use the NAC future. You need GRE PSR-500 or PSR-600 scanner.
Those will tell you what NAC tones that APCO-25(P25) signal it's using.

Like if you had a PSR-500/600 and you found a new repeater with a NAC of 165.
then you would know(likely) it be for Midland, County.

[ampulman]

Originally Posted by MtnBiker2005

but IF you want to use the NAC future. You need GRE PSR-500 or PSR-600 scanner.
Those will tell you what NAC tones that APCO-25(P25) signal it's using.

Like if you had a PSR-500/600 and you found a new repeater with a NAC of 165.
then you would know(likely) it be for Midland, County.

As I am now (due to the prospect of Uniden offering upgrades to 396's) trying to learn about NACs, I have a question or two. Hope you can address them.

I have no P25 systems within range. I have programmed a system, but it is a ride away and only tests once weekly for a brief time period, so I haven't been able to 'catch' them (Mercer County, NJ). Just checked data base. Only 2 TGs, no NACs but a WACN (I get that).

Now, under normal circumstances, would a P25 system have a different NAC for each talk group? Does the system broadcast both an NAC and TGID? In other words, what would be displayed on a scanner that doesn't decode NACs? Could one enable/disable TGs at will?

While I monitor some frequencies (analog) that are shared by different communities, and use the same PL (can't figure that one out) and it doesn't seem to be a problem (interference-wise), is there really a problem (interence) with P25 systems?

Thanks.

AM

[MtnBiker2005]

Read this post about NAC's on Trunked system.
http://www.radioreference.com/forums...25&postcount=6

[ampulman]

Just looking for answers to my questions, which can be answered yes or no.

1. Are NACs limited to Apco-25 (air exclusive) systems only?

2. Do systems using NACs broadcast a TGID?

3. Will a digital-capable scanner, e.g., BCD396T (in its present form) decode groups using NACs?

Thank you.

AM

[ka3jjz]

Originally Posted by ampulman

Just looking for answers to my questions, which can be answered yes or no.

1. Are NACs limited to Apco-25 (air exclusive) systems only?

2. Do systems using NACs broadcast a TGID?

3. Will a digital-capable scanner, e.g., BCD396T (in its present form) decode groups using NACs?

Thank you.

AM

1. Yes, AFAIK - as described in the wiki

2. No - there are some P25 conventional usage that NACs can be used with - for example, TSA frequencies

3. Yes, though nothing in the Uniden world (yet). The GRE PSR-500 and 600 can.

73 Mike

[wayne_h]

Originally Posted by ka3jjz

2. No - there are some P25 conventional usage that NACs can be used with - for example, TSA frequencies

A TG ID value is always sent as it's my understanding that section of the bitstream has to contain something. It's up to the radio to acknowledge it. So, technically, it's a yes. Basically the same as a NAC; it's always gonna be there.

[ka3jjz]

Wayne, I must admit to a little confusion. How could a TG ID be sent on a conventional frequency? Or does the NAC take the place of a TG ID when the bitstream is sent? As far as I understood it, the use of a NAC is similar to a PL on a conventional non P25 frequency; it wouldn't contain system information, would it? Or is that too a part of the bitstream?

73 Mike

[MattSR]

APCO25 has a conventional TG as well for use on standard, non trunked P25 repeaters.

It is separate from the NAC code - however it serves the same purpose - it provides logical grouping of users on a channel.

Cheers,
Matt

[ka3jjz]

Ah, that's interesting Matt - that's one I didn't know. 73 Mike

[ampulman]

Originally Posted by ka3jjz

1. Yes, AFAIK - as described in the wiki

2. No - there are some P25 conventional usage that NACs can be used with - for example, TSA frequencies

3. Yes, though nothing in the Uniden world (yet). The GRE PSR-500 and 600 can.

Thanks Mike. In my case, much ado about nothin'. As there are no active P25 systems near me, I don't need that feature just yet.

Perhaps soon, Uniden will provide the function via an upgrade.

AM

[wayne_h]

Originally Posted by MattSR

It is separate from the NAC code - however it serves the same purpose - it provides logical grouping of users on a channel.

In addition it is transparently passed when operating via a repeater/station versus a NAC, which is evaluated and then retransmitted per the station programming. TG IDs can change at will without any need to update the station's programming.

[ampulman]

Originally Posted by wayne_h

A TG ID value is always sent as it's my understanding that section of the bitstream has to contain something. It's up to the radio to acknowledge it. So, technically, it's a yes. Basically the same as a NAC; it's always gonna be there.

Good news, if I understand correctly.

Just to be sure: my question #3 referred to hearing the digital group on my 396, not displaying the NAC on the display.

AM

[wayne_h]

Originally Posted by ampulman

Just to be sure: my question #3 referred to hearing the digital group on my 396, not displaying the NAC on the display.

The 396 and 996 completely ignore all data (the CAI data) except for the section used for voice. When the scanner is decoding the data and there is no voice it will display "LNK". For example, P25 repeaters when transmitting a hang-time after the user unkeys is basically null data in the voice section. This is a nice hint to determining whether the transmission is through a repeater or simplex.