NAC Tones

[Tophtoh]

I know digital radio uses something called NAC tones, would anyone have a list of what they are? Are they 67.0, 023... like PL and DCS or... thanks.

 

[SCPD]

It's not a tone. It's a three digit number. Each digit is hexadecimal digit so it can 0 through 9, or A through F. It can serve the same purpose as a CTCSS tone or DCS code. The three digits can be any one of those values so there's not really a point in having a list of all possible NAC codes.

-rick

 

[mam1081]

Some good ones to remember though are these:

$293 - default NAC
$F7E - a receiver set on this will unsquelch with any incoming NAC
$F7F - a repeater set on this will allow incoming signals to be repeated with the NAC code intact.

Some APCO-25 users don't use NAC codes exclusively - they use APCO-25 talkgroups (similar to TRS, but all on the same freq). They are arranged just like in a TRS ($0000 to $FFFF) and there are 65,536 possible groups.

 

[FPO703]

How does one determine these Network Access Codes?

 

[N_Jay]

How does one determine these Network Access Codes?

They are like PLs (or DPLs)

You choose them when you set up the system.

You can read them with a service monitor.

 

[FPO703]

You can read them with a service monitor.

And, who can afford one of those?

 

[N_Jay]

You can read them with a service monitor.

And, who can afford one of those?

:wink:

 

[x2o2]

OK, are they 023, 025 ect. like DPL tones. or PL Tones 67.0... or are they different?

 

[bigreddawg76]

I see P25 systems in the RR Database that list a PL/DPL code. I was under the impression that PL/DPL could not be used in P25 systems since they use NACs. Am I mistaken?

 

[x2o2]

You are correct, they cannot be used with digital modulation, but there are similar three digits codes which are NAC Codes. I am just wondering if they're the same set as digital pl... such as: 023, 125, 306 ect. Any help would... help.

 

[N_Jay]

You are correct, they cannot be used with digital modulation, but there are similar three digits codes which are NAC Codes. I am just wondering if they're the same set as digital pl... such as: 023, 125, 306 ect. Any help would... help.

They serve the same (or similar) function, they work in a whole different way.

All codes are valid, unlike DPL.

The codes are sent as part of the signal, not under the signal, as DPL is.

They are in Hex, not Decimal.

Hmm, well they are three digits, so that is the same.

 

[N_Jay]

I see P25 systems in the RR Database that list a PL/DPL code. I was under the impression that PL/DPL could not be used in P25 systems since they use NACs. Am I mistaken?

You are not mistaken, PL and DPL are incompatable with P25.

P25 provides a feature called NAC that performs a similar function, but is implemented in a commpletely different manner.

 

[Joseph11]

If a DPL code or PL tone is listed along with an APCO-25 frequency, it usually means that it operates in mixed mode and when it's used in analog mode it uses that DPL code or PL tone.

 

[scannerman82]

conversion table from CTCSS to NAC codes

CTCSS
NAC Code
67.0 Hz
$29E
69.3 Hz
$2B5
71.9 Hz
$2CF
74.4 Hz
$2E8
77.0 Hz
$302
79.7 Hz
$31D
82.5 Hz
$339
85.4 Hz
$356
88.5 Hz
$375
91.5 Hz
$393
94.8 Hz
$3B4
97.4 Hz
$3CE
100.0 Hz
$3E8
103.5 Hz
$40B
107.2 Hz
$430
110.9 Hz
$455
114.8 Hz
$47C
118.8 Hz
$4A4
123.0 Hz
$4CE
127.3 Hz
$4F9
131.8 Hz
$526
CTCSS
NAC Code
136.5 Hz
$555
141.3 Hz
$585
146.2 Hz
$5B6
151.4 Hz
$5EA
156.7 Hz
$61F
162.2 Hz
$656
167.9 Hz
$68F
173.8 Hz
$6CA
179.9 Hz
$707
186.2 Hz
$746
192.8 Hz
$788
203.5 Hz
$7F3
206.5 Hz
$811
210.7 Hz
$83B
218.1 Hz
$885
225.7 Hz
$8D1
229.1 Hz
$8F3
233.6 Hz
$920
241.8 Hz
$972
250.3 Hz
$9C7

 

[ElroyJetson]

That conversion is completely useless and meaningless. There's no correlation. It could only help someone to understand its functionality. It's VAGUELY similiar to what a PL tone
does, but it's all digital including the voice. Purpose: To separate different users engaged in different activities from each other so they don't hear anyone but their own user group.

And only a SUITABLY equipped service monitor would decode it. A P25-equipped service monitor.

Elroy

 

[16b]

If anyone is still confused as to the purpose/meaning of NAC codes (or anything else having to do with P25), read this:
http://www.danelec.com/pdfs/TG-001-2-0-0 P25 Training Guide.pdf

Here are some choice excerpts:

NAC codes are user programmable and are typically used to control network access but may also be used to steer repeater functions. NAC codes are used the same way as an analog CTCSS tone (or DCS code). NAC codes minimize co-channel interference and allow repeater addressing by keeping the receiver squelched unless a signal with a matching NAC arrives. The NAC code’s 12-bit field ranges from hexadecimal $000 to $FFF and contains 4096 addresses (significantly more than the standard CTCSS and DCS tones).

In reference to scannerman82's post:

Early TIA documents specified a formula for converting analog CTCSS tones and DCS codes to specific NAC codes. Those documents have
since been removed and the selection of NAC codes has been left to the user.

The whole guide is a very good read for someone who is really interested in understanding the basics of P25. It does not provide the quick/easy answers to many questions. You have to be willing to spend some quality time reading ( :lol: ) it to get much out of it.

 

[WayneH]

That conversion is completely useless and meaningless.

No it's not. That table is used by Fed fire agencies for digital operations. I have it listed in a few guides and I think a Thales manual I have lists it also. Outside of Fed Fire there are some other federal agencies who took their analog PL and converted just as done above when doing the transition to digital.

Also, you seem to be unaware that the new GRE radio does decode NACs. Get with the times man!

 

[detroit780]

Service Monitor

The PSR-500 decodes NAC's just fine. It's a lot cheaper then a service moniotor too and the conversion is not useless it's good information and it works. Most agencies use the converted NAC from their old CTCSS tone. Not all the time but generally. Even the 700MHZ mutual aid frequencies will use a conversion of the current 800MHz Mutual Aids CTCSS of 156.7 which makes it $61F

If you don't beleive it surf the net for about and hour and you'll find 100's of documents supporting this.

That conversion is completely useless and meaningless. There's no correlation. It could only help someone to understand its functionality. It's VAGUELY similiar to what a PL tone
does, but it's all digital including the voice. Purpose: To separate different users engaged in different activities from each other so they don't hear anyone but their own user group.

And only a SUITABLY equipped service monitor would decode it. A P25-equipped service monitor.

Elroy

 

[n1das]

And only a SUITABLY equipped service monitor would decode it. A P25-equipped service monitor.

P25 NACs can be decoded by including but not limited to:
- P25 compliant radio equipment
- P25 service monitors / test equipment
- PC software
- some scanners (GRE PSR-500)

I wish somebody had told me that only a service monitor could decode it before I tried UniTrunker's standalone P25 NAC decoder program. It listens to discriminator audio from a scanner (doesn't have to be P25-capable) and is fed into the PC's sound card audio input. UniTrunker's "kNACk" decoder program works as advertised. Using the "the kNACk" program, I'm decoding and reading NACs on P25 conventional channels in my area WITHOUT a "SUITABLY equipped" service monitor!

My next scanner someday will have NAC display and decode capability, possibly a GRE PSR-500.

 

[N_Jay]

P25 NACs can be decoded by including but not limited to:
- P25 compliant radio equipment
- P25 service monitors / test equipment
- PC software
- some scanners (GRE PSR-500)

I wish somebody had told me that only a service monitor could decode it before I tried UniTrunker's standalone P25 NAC decoder program.

Guess it depends on who you ask.