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Old 06-20-2018, 6:08 PM
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Question Encryption on 7TAC73

I've heard several encrypted transmissions on 7TAC73 (774.106250) this afternoon. NAC is $530.

Encryption is not supposed to be used on interoperability channels.

NAC $293 is supposed to be used on the 700 MHz interoperability channels.

NAC $530 is one of the two RWC trunked system NACs. $531 is the other.

As for adjacent frequencies, 774.093750 is a control channel on the AZWINS Thompson Peak site, with a NAC of $150, and 774.118750 is 7AG85, which is also supposed to use a NAC of $293, so it's not bleed over.

I believe I've heard encryption on 774.993750, one of the national low power/itinerant channels, however with a NAC of $293, in the past as well.

Are RWC user agencies using encryption, and the $530 NAC in some cases, on the 700 MHz interoperability channels?

John
Peoria
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Old 06-20-2018, 6:55 PM
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774.10625 has some footnotes in the APCO/NPSTC Interop guide http://www.napco.org/Resources/NPSTC...aming-2017.pdf

90.531(b)(1)(iii) (iii) Narrowband trunking Interoperability channels. The following Interoperability channel pairs may be used in trunked mode on a secondary basis to conventional Interoperability operations

That frequency is used in the Statewide Site On Wheels:
Statewide Emergency Mobile System Trunking System, Mesa, Arizona - Scanner Frequencies
I can confirm that in the past, this frequency was used as a voice frequency for this system. I have only monitored this system twice, and I did not catch the NAC. It might be part of this system or another mobile trunked system that is covered under the State's 700mhz license. Since $530 is a NAC that the RWC likes to use, maybe they have a mobile trunked system that we have not discovered yet?

Last edited by cellphone; 06-20-2018 at 7:01 PM..
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Old 06-20-2018, 7:11 PM
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I wonder why the statewide deployable mobile system doesn't use the frequencies that are actually allocated for that purpose?

https://wiki.radioreference.com/inde...runked_Systems

Maybe because the frequencies were set aside after Mesa put their system in operation?

John
Peoria
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Old 06-20-2018, 7:47 PM
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I also have another theory. You might be hearing an image frequency. 774.10625 is a GRE Scanner image frequency of 799.09375. 799.09375 is licensed as an input frequency of Simulcast H, which happens to use a NAC of $530.

RWC License for 799.09375:
https://www.radioreference.com/apps/...llsign=WQJU870
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Old 06-20-2018, 8:06 PM
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I'm only hearing encrypted transmissions. I've not heard any clear traffic that should also be cycling around to that voice channel. I would also think that I'd be too far from Simulcast H to pick up any mobile or portable transmissions on the input, especially since I don't use an external antenna.

Unless a Scottsdale officer or detective was much closer to me but was still able to access Simulcast H from where they were, although I would think that they would affiliate with Simulcast B, if not G if they were far enough west out of Scottsdale, and their TG was authorized on B or G, I don't think that that's what I'm hearing.

John
Peoria

Last edited by KB7MIB; 06-20-2018 at 9:01 PM..
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Old 06-20-2018, 8:20 PM
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Quote:
Originally Posted by KB7MIB View Post
I'm only hearing encrypted transmissions. I've not heard any clear traffic that should also be cycling around to that voice channel. I would also think that I'd be too far from Simulcast H to pick up any mobile or portable transmissions on the input, especially since I don't use an external antenna.

Unless a Scottsdale officer or detective was much closer to me but was still able to access Simulcast H from where they were, although I would think though that they would affiliate with Simulcast B, if not G if they were far enough west out of Scottsdale, and their TG was authorized on B or G, I don't think that that's what I'm hearing.

John
Peoria
Are you receiving and able share any radio IDs?

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Old 06-20-2018, 9:00 PM
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I don't normally have that feature enabled on my PSR-500, although I can, and see if I can catch any. I don't have a computer, so I can't run ProScan or some such.

I'll enable radio ID's, and sit on it and see if there's anymore activity.

John
Peoria
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Old 06-20-2018, 9:27 PM
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Quote:
Originally Posted by KB7MIB View Post
Encryption is not supposed to be used on interoperability channels.
"At 700MHz, the FCC prohibits encryption only on the nationwide interoperability calling channels. There is no FCC prohibition re encryption on the 700 MHz band nationwide interoperability tactical channels"
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Old 06-20-2018, 9:29 PM
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Encryption is permitted on the 700 MHz TAC channels. 700 IO channels must be P25.
The calling channels must be in the clear.
The other bands National IO channels must be analog, which basically precludes encryption from them.
But P25 encryption is legal on a 7TAC.
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Old 06-20-2018, 9:41 PM
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I was not aware of that. That may also explain the encryption on the low power and itinerant channels.

Is the $293 NAC also not a strict rule? Can any NAC be used?

John
Peoria
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Old 06-21-2018, 3:33 PM
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In the past couple of years, our 7TAC73 (774.106250) had $168 for a NAC. I don't suppose the default is a hard and fast rule, though it would make sense that it should be. It's no longer used for the purpose I was involved in. Ill ask around and see if it's still in the codeplug as the same or compliant with the NIFOG stuff.
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Old 06-21-2018, 5:17 PM
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14+ hours, from about 7pm last night to about 2pm this afternoon, with no further activity.

John
Peoria

Quote:
Originally Posted by KB7MIB View Post
I don't normally have that feature enabled on my PSR-500, although I can, and see if I can catch any. I don't have a computer, so I can't run ProScan or some such.

I'll enable radio ID's, and sit on it and see if there's anymore activity.

John
Peoria
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Old 06-21-2018, 5:39 PM
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I don’t believe it’s in the rules. I think the rules just say P25 on the 700 IO channels. But either a State or RPC (depending on who elected to control the 700 IO) could set requirements.
The NIFOG is guidance, not law.
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Old 06-21-2018, 7:22 PM
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Right, I was referring to AZ use, wasnt it prescribed in the documents outlining AIRS? I remember seeing it somewhere for AZ use, not Fed. I know the feds recommend a standardized NAC, least every briefing I attend it's usually in there.
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Old 06-21-2018, 8:45 PM
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If I run across anymore encryption on any of the 700 MHz interoperability channels, I'll try to get radio ID's and post them.

John
Peoria
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