SDS100/SDS200: "use trunk NAC", what does this setting do?

[N9NRA]

Hey, sorry i`ve not been around lots lately, stuff happening around here wit a big remodel of the building i live in , Anyway, i`ve seen a setting on my SDS100 called, "use (or set) trunk NAC", what will this do? I`ve noticed that when i scan a digital trunked system and just let the unit detect (but i don`t set) the trunked NAC it will show what the NAC is when the unit is just hearing the c-channel, but when a transmission comes up the NAC is not displayed, so using the trunked NAC feature would seem to cause ya to NOT hear anything, as any transmissions wouldn`t match the set NAC, am i correct, or am i missing something here? Thanx! 73. N9NRA

 

[737mech]

Think of it like a ctcc/dcs tone for a digital channel. Same function. Helps scanner sort a little further to what you want to hear. Not too common in my area for more than one NAC on the same freq but I guess it's possible where many P25 systems are in use?

 

[doctordialtone]

am i missing something here?

This explains NAC in the SDS100

 

[tvengr]

The SDS100 can use site NAC. Statewide trunked systems often reuse control channel frequencies on sites spaced wide apart. If you have all of the sites in the state programmed, you may see a site that you think is far away when in reality it is another site which uses the same frequencies as your local site. Using site NAC, the scanner is able to differentiate between sites using the same frequencies. Site NAC can also prevent the scanner from locking on a wrong control channel frequency.

 

[N9NRA]

Okay, so i`ll still hear anything that comes up on a site that i`ve set to use the NAC, i just won`t hear anything on a site that uses the same freqs as the one i`m listening to, in other words, i`ll still hear stuff, just not stuff on a site that uses the same freqs for the C-channel right? Thanx! 73. N9NRA

 

[tvengr]

If the site NAC is correct, you will receive all of the frequencies on that site when within range. If the site NAC is incorrect, you will be blocked from receiving that site. If you are close to a site and are not able to receive it, set the scanner to ignore site NAC. If you then receive that site, the site NAC is incorrect. If you do not have a site NAC programmed, the site NAC will flash on the screen while the site is being received (if site NAC is used for that site and it is programmed to be shown on the customized display). You will not hear anything on another site using the same frequencies.

 

[dave3825]

@tvengr What should happen when you have a site nac set, and your not in range of that sites cc, but another freq in the site is an active cc within range, on a different site, with a different nac?

 

[tvengr]

You can receive a site only when the site NAC transmitted by the control channel matches the NAC you have programmed for a site in the scanner. As stated earlier, the NAC acts like a PL tone for a site.

 

[dave3825]

I know the function of a nac and all that, I guess what I am asking is if one has a site nac set for a site, and one of those sites freqs is an active cc on another site, should there be any indication on the screen that it is seeing the other freq even tho its nac is different then the set site nac? Like signal strength, data and rssi value?

 

[werinshades]

I know the function of a nac and all that, I guess what I am asking is if one has a site nac set for a site, and one of those sites freqs is an active cc on another site, should there be any indication on the screen that it is seeing the other freq even tho its nac is different then the set site nac? Like signal strength, data and rssi value?

If your programming is set up correctly, that would be a no. If you want to see any additional information about that frequency, use conventional search and see if any other NAC information comes up.

 

[dave3825]

If your programming is set up correctly, that would be a no.

This is site 114 set to "use site nac" of 4F4. It was seeing signal on 170.9125 and displaying "set" site nac 4F4. 170.9125 was the active cc on site 127 and that site's nac is 4F7, yet it was displaying the nac that's set for site 114, 4F4 even though its not the nac of the freq it was showing as active. The active cc for site 114 was 168.9125 and was completely out of my range.

This is the same site 114, but with site nac search on, and receiving the same freq of170.9125. In this pic, it displays the correct nac of 4F7 and also id's the site as 127. In the first pic it was not displaying the site id.

Seems to me if you have a site nac set, it will display that nac even if its seeing a cc with a different nac.

 

[werinshades]

This is site 114 set to "use site nac" of 4F4. It was seeing signal on 170.9125 and displaying "set" site nac 4F4. 170.9125 was the active cc on site 127 and that site's nac is 4F7, yet it was displaying the nac that's set for site 114, 4F4 even though its not the nac of the freq it was showing as active. The active cc for site 114 was 168.9125 and was completely out of my range.

This is the same site 114, but with site nac search on, and receiving the same freq of170.9125. In this pic, it displays the correct nac of 4F7 and also id's the site as 127. In the first pic it was not displaying the site id.

Seems to me if you have a site nac set, it will display that nac even if its seeing a cc with a different nac.

Nope...if it's programmed properly, it will trunk track the control and voice channels of the NAC that's set. This looks like it's in NAC Search and you don't have it programmed properly.

I just saw your other post and linked it...and that still looks like NAC Search, and you're receiving another close by control channel/system. But I think you said you're sending it back, so it's a moot point.

 

[dave3825]

Its programmed correctly, I can assure you. And in the first pic, that was taken with site nac "set" to 4F4 for site 114 so it was not in nac search. The active cc that day was 168.9125 and was out of my range. 170.9125 at the same time, was the active cc on site 127 nac 4F7. In the pic it clearly shows it sees 170.9125 but displays 4F4 because that's the nac set for the site.

site 114 freqs and nac 4F4 168.9125c 170.9125c
site 127 freqs and nac 4F7 170.5625c 170.9125c 170.9625c

The second pic is the same site, 114, that's out of range, when it landed on on 170.9125, it displayed the correct nac, it was flashing 4F7 meaning it was in nac search..

 

[werinshades]

Its programmed correctly, I can assure you. And in the first pic, that was taken with site nac "set" to 4F4 for site 114 so it was not in nac search. The active cc that day was 168.9125 and was out of my range. 170.9125 at the same time, was the active cc on site 127 nac 4F7. In the pic it clearly shows it sees 170.9125 but displays 4F4 because that's the nac set for the site.

site 114 freqs and nac 4F4 168.9125c 170.9125c
site 127 freqs and nac 4F7 170.5625c 170.9125c 170.9625c

The second pic is the same site, 114, that's out of range, when it landed on on 170.9125, it displayed the correct nac, it was flashing 4F7 meaning it was in nac search..

I also remember reading about an issue with decode in that band range, so look into that too. I have NAC's set on all my Trunking systems, Color Codes on MotoTRBO and Channel ID's on NXDN Trunking and all is working well as advertised. You have other problems with interference or something, but I haven't ever experienced it.

 

[dave3825]

It is definitely not interference. Its clearly showing activity on a freq in the site that happens to be part of another site as an active cc.

 

[werinshades]

It is definitely not interference. Its clearly showing activity on a freq in the site that happens to be part of another site as an active cc.

In another thread, there's mention of issues decoding in the upper VHF band FYI. Did you append this system, or manually program it? If it's appended, try programming it yourself via Sentinel. Are only the Primary and alternate control channels programmed and not the voice frequencies? Do you have the NAC programmed at the Site level or just the System? Did you try a different SD card, delete all the programming off it and try and start from scratch? Did you try using the different filters at the site level, not the Global Filter? And...what do you think it is?