Astro Network ID

[nickjc]

Hey All,

Did a search and did not find any data....

Ok some questions.....

1) Being an astro system can have a differing network ID for both TX and RX, not having the same system ID in a radio will preclude you from 'hearing' that transmission correct?

2) Is there a way to set-up an astro radio so as to not need the particular net id to 'decode' all astro signals it hears?

3) if there is an astro system repeater, can it be, and is it, typically setup to only hear/use one network ID..or can it pass ANY it hears....

4) If the above is correct that is can pass any network ID it hears, will it also *decode* all it hears....

thanks

Nick

[ddearth]

Just take the mic off of the clip, it'll pass everything.

[tvsjr]

1. Yes, TX and RX NACs are selectable individually. I know of one user who uses simulcast transmitters with "manual voters" - all repeaters transmit NAC 001, but you pick which receiver you want with the NAC you transmit (001, 002, 003, etc.)

2. Yes, there is an option for Digital CSQ. Transmissions in this mode will be made with NAC 293, but you'll hear everything.

3. I believe either is possible.

4. What do you mean by decode? If you want analog audio output at the repeater, I believe you'll need a DIU3000. If my understanding is correct, a Quantar decodes the data stream, applies FEC, reframes and data, and retransmits it. I don't believe the Quantar has any vocoder on board, hence it can only play with the bits, not convert them to analog.

Uh, take the mic clip off? Shoo, troll.

[nickjc]

1) I understand makes perfect sense....all users receive NAC 001...but use NAC #2 for inuput site # 2 and so on..

2)

2. Yes, there is an option for Digital CSQ. Transmissions in this mode will be made with NAC 293, but you'll hear everything.

So if you set your NAC to 293...you can here ALL NAC codes....hmmm that seems strange or maybe I misunderstand...it seems NAC 293 is the *common* NAC to use if you do not have a particualr one, kind of like a general access NAC. Given this, if I do not know the NAC code of a particalur system setting my receiver to NAC 293 should allow me to hear all NAC's...???

3) In your experience which is typical.... do most systems lock the NAC code, or, do they have multiple NAC's in their fleet...I would say then that the repeater system will most likely pass all NAC's it hears and not be NAC specific..is the repeater NAC dependent to access it...?

4) Bad choice of wording (*decode*)....assuming the repeater is setup that it will allow any and all NAC's it hears to pass....

The reasoning for the questions are as follows....a client of our that we do Life Safety and Security work with is looking to implement their own P25 System. My contact knows I have some 'radio' experience and asked me specific questions that I, frnakly, did not know...

They are concerend with someone *piggybacking* on their system without their knowledge. Their RF analyst says it is possible that if they have their own P25 repeater system..(only one site)...that the repeater will pass all P25 signals it hears and without the client knowing the other 'piggyback' users NAC, they will never be able to tell they are on the system....

Any help on this would be great....

[apco25]

Set the quantar to ONLY respond to a specific NAC. If you set it to 293 it will pass any NAC sent.

Also don't forget you can setup digital talk groups like PL or DPL used to segment different users.

[nickjc]

If you set the quantar to a specific NAC it will suppress other NAC's...? Correct???

But if the quantar needs to pass other NAC's it should be set to 293..

This organization does not necessarily want all users to be on the same NAC..

Operations and Facilities on one
Security on another etc...

If the quantar is set to 293....and passes other NAC's can portable/mobile receivers hear the other NAC's being passed..??? For example:

The quantar is set to 293 and will pass all NAC users....

Security is NAC #1
Operations NAC #2
Facilities NAC #3
Personnel Nac # 4

Can the security director set his radio to the 293 NAC and hear all NAC traffic..all other users not set to NAC 293 will ONLY hear their group traffic....then if he needs to communicate with a particular group he can transmit on that particular NAC...

Am I understanding this correctly??

[tvsjr]

Yeah, that'll probably work. However, the right way to do it, as apco25 suggested, is using the digital talkgroup features, which is really what you want (you only have one network, but you want multiple logical "channels" eg talkgroups).

All ASTRO radios have the option to do the P25 talkgroups. Look around in your software and you should find it.

[nickjc]

got it thanks !

nick

[515]

According to the latest Project 25 spec, NAC F7E is the current 'wildcard' NAC value, but its not exactly "Digital CSQ". If F7E is entered in the RX Network ID field, the radio should unmute on any NAC. For true "Digital CSQ" functionality, you'll need to use F7E in conjunction with talkgroup 65535, which is the P25 'wildcard' or 'all-call' talkgroup. (of course on Motorola radios, you can disable talkgroups)

293 was defined as a 'carrier squelch' NAC years ago, but that is no longer the case. Consider it more of a 'factory default' NAC. The Motorola radios are just now getting with the program...

Only the latest Motorola Astro radios with late firmware correctly implement F7E, though (XTS5000, XTS2500, and XTL5000, etc.) On the older XTS3000/Astro Saber/Astro Spectra series, F7E is just a standard NAC value, so you won't get any 'carrier squelch' functionality by programming it in. The Thales Racal 25 and EF Johnson radios correctly support the F7E NAC, though.

The R05.00.00 XTS2500/5000 CPS help file states:

NAC Monitor = F7E (Hex)

When this Rx NAC ID (Network Access Code) is set to “F7E”, the radio unmutes to any ASTRO call regardless of the call’s NAC ID or the radio’s ASTRO Rx Unmute Rule set for the current channel.
Note: The Rx Unmute Rule for the channel is defined in the Conventional Personality. The Conventional Personality is selected for this channel from the Personality # field.

The factory default is 293 (Hex)

It is important to note that F7E should only be allowed as a RECEIVE NAC. The newer Motorola radios won't allow you to enter F7E in the TX NAC field.

The big advantage of F7E over the old Motorola "Digital CSQ" functionality is that you can transmit any NAC you program in, but still receive any NAC. With the old "Digital CSQ", you were forced to TX 293.


The latest versions of the Quantar also support F7E on RX, and the old "293 Digital CSQ" functionality. With F7E on the Quantar, you can setup your repeater to repeat any digital signal, but transmit a single NAC out of the repeater (like a carrier squelch repeater that has a tone on the output).

The latest version of the Quantar aslo supports F7F, which is a reserved value for "digital community repeater" operation. F7F programmed in the latest Quantar will cause the station to retransmit whatever NAC is on the input (like a CSQ repeater that passes tones). According to the P25 spec, F7F is not supposed to be transmitted, or allowed in mobile/portable radios. As with F7E, the older XTS3000 series don't prohibit you from using F7F.

With the latest Quantar, you have two ways of implementing a "community repeater". One way is with F7F in the Quantar, and separate users with different NAC's. The other way is to use only one NAC in the Quantar, and sepearate users with TG's. I prefer the TG method, since you can restrict access to the repeater to those users who have the correct NAC programmed.

[ddearth]

It is as simple as it sounds....take the mic off of the clip/hangup and the radio will pass any all NACs (monitor mode?) Also, it is correct that Motorola didn't implement the NAC F7E properly and in accordance with EIA/TIA rules. Until recently all of Motorola's Digital radios have been in essence, in non-compliance with this requirement. Now they seem to have it fixed, not sure how you would remedy this situation with the older Astro Spectras though....just starting to get back into Motorola equipment.

[allplowedout]

I knew this is possible on conventional systems, ie..Single channel systems?

I thought it was only do-able in trunked configurations...

Quote:
Yeah, that'll probably work. However, the right way to do it, as apco25 suggested, is using the digital talkgroup features, which is really what you want (you only have one network, but you want multiple logical "channels" eg talkgroups).

All ASTRO radios have the option to do the P25 talkgroups. Look around in your software and you should find it.

[nitornemo]

Interesting thread.....
Answers some questions I had on my X3k 800MHz.

However My X3k defaults to a NAC of "3F3" when a conventional is Rx set to Non-Astro.

I was also wondering how the NAC applied to a trunking system.

I added a Trunking System for digital (Same CPS screens as the analog II system)and enabled "ASTRO Capable System".
Followed with a personality that is "ASTRO AG/FLT Strapping" strapped. Added the "Astro" TG's but was looking for the NAC....not there?
Does the NAC apply in Astro trunking?
or does the increase in the TG ID # automatically adapt this as a NAC equivalent?

It is important to note that F7E should only be allowed as a RECEIVE NAC. The newer Motorola radios won't allow you to enter F7E in the TX NAC field.

The big advantage of F7E over the old Motorola "Digital CSQ" functionality is that you can transmit any NAC you program in, but still receive any NAC. With the old "Digital CSQ", you were forced to TX 293.

[tvsjr]

I knew this is possible on conventional systems, ie..Single channel systems?

I thought it was only do-able in trunked configurations...

Quote:
Yeah, that'll probably work. However, the right way to do it, as apco25 suggested, is using the digital talkgroup features, which is really what you want (you only have one network, but you want multiple logical "channels" eg talkgroups).

All ASTRO radios have the option to do the P25 talkgroups. Look around in your software and you should find it.

Yes, there is a conventional talkgroup function in the P25 standard. You can even run talkgroups on a simplex channel, if you so desire.

[tvsjr]

Interesting thread.....
Answers some questions I had on my X3k 800MHz.

However My X3k defaults to a NAC of "3F3" when a conventional is Rx set to Non-Astro.

I was also wondering how the NAC applied to a trunking system.

I added a Trunking System for digital (Same CPS screens as the analog II system)and enabled "ASTRO Capable System".
Followed with a personality that is "ASTRO AG/FLT Strapping" strapped. Added the "Astro" TG's but was looking for the NAC....not there?
Does the NAC apply in Astro trunking?
or does the increase in the TG ID # automatically adapt this as a NAC equivalent?

NAC is automatically calculated for trunking (at least 800, not sure about OBT) based on the System ID. This is, at least, true for Type II systems with digital voice. Never played with a true ASTRO P25 system, not sure how it works there.

[alex_davies]

The Astro signal is viewed as a "data link" between communication devices, whether is over the air RF, a modem signal, or a V.24 link this data link can be broken down into two different components: control signals, and voice signals. The control portions are called"LC" or Link Control" data. The voice portion is called an "LDU", or Link Data Unit. These two components are sent in a "packet" of data, or Astro Packets. The LCs contain control information that give the receiving unit a wide variety of information, such as what the System ID is the Talk Group ID, Network ID, etc. The LDU contains the voice portion of the call. All Astro products understand the LC info, and know what is an LDU. The Quantar does not decode an LDU, but it can decode the LCs. Only a subscriber radio and a DIU can decode both the LCs and LDUs. We can also Encrypt the Astro data stream for more with the DIUs and subscribers. They simply have to have the same encryption key to unscramble the 1s and 0s.

From a Technician's point of view, there is virtually no way of decoding the Astro or C4FM from the carrier. The LCs and LDUs are embedded within the Astro signal, and cannot be decoded without a DIU or subscriber radio. . I suppose there is some piece of equipment capable of doing this, even then, you will only hear audio.
The actual decoding of the Astro LCs and LDU is done in the DSP of the Station Control Module The DSP SW gives the Host SW an Opcode, and we act on it. We don't deal with the actual 1s and 0s.

Enjoy