Decoding astro nac codes

carbineone · Post by **carbineone** » Fri Oct 15, 2004 11:12 am

Does anybody know of a way to decode nac codes ? I was thinking maybe trunker could be used somehow.

SNO-MAN · Post by **SNO-MAN** » Fri Oct 15, 2004 1:33 pm

I used a P25 Srvice monitor $25,000.00

ASTROMODAT · Post by **ASTROMODAT** » Sun Oct 17, 2004 1:35 pm

I'm not positive on this, but I think you can also decode NAC addresses via a DIU3000, which would only involve $10,000. I believe this is possible by placing the DIU in the service mode.

Larry

515 · Post by **515** » Mon Oct 18, 2004 9:33 am

I assume you are talking about decoding the NAC off the air... If so, a P25 service monitor is about the only way to go.

I'm not sure if the DIU can decode the NAC or not, but even if it could, you would still need a Quantar to use as a receiver. Not cheap.

If your desire is only to listen, you can use the Digital Carrier Squelch option on Motorola radios. If you have another radio brand, you could probably use the special "reserved" NAC of F7E (programmed into the RX NAC field). This special NAC instructs the radio to unmute on any NAC. You would want to use this in conjunction with the Talkgroup of 65535, which allows unmute on any talkgroup. This F7E "reserved" NAC should not be transmitted according to the P25 spec, but many radios do allow it as a TX NAC anyway. You can program F7E into Motorola radios, but they treat it as just any other NAC.

Unfortuantely, with Motorola radios, when you use Digital Carrier Squelch, your transmitted NAC is forced to 293, which is stupid.

Other than that, my only other suggestion is to try a NAC of 001. I've seen a surprising number of P25 conventional repeaters out there using this NAC.

Post by **Wowbagger** » Mon Oct 18, 2004 10:21 am

I would ask "Why do you WANT to decode the NACs?"

I know that when we demonstrated our P25 control channel logger, it caused Great Consternation And Knashing Of Teeth Among Three Letter Agencies because it would reveil, among other things, the NAC for a network.

The reaction was 'They can see our control channel info - cool. Uh, waitaminute - THEY CAN SEE OUR CONTROL CHANNEL INFO - $H!T! We have to encrypt the control channel now!"

carbineone · Post by **carbineone** » Tue Oct 19, 2004 3:02 am

I just wanted to know for monitoring purposes. Back when the feds were on analog you could usually tell who it was by the pl code. I was thinking maybe they were going to be assigned different nac codes for different agencies.

SNO-MAN · Post by **SNO-MAN** » Tue Oct 19, 2004 3:10 am

Chances are that the Quantar is running the same NAC and different TG's ...Here in NH the Digital ID's show which division is on the air with the first digit prefix....

Decoding astro nac codes

Decoding astro nac codes

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