Question about comm protocol

[dgoodson]

I monitor what is reported to be a Federal Law Enf frequency with my SDS200. I have it programmed as a digital frequency 167.3125 with NAC 167, I actually have the NAC set to "search".

Several times a day I will hear a short transmission, perfectly clear and legible, along the lines of "Base to John", or "Base to Cindy" or something like that. I never hear a response or any other clear transmissions, nor do I ever hear the hail repeated- its always a one time hail with no other information or elaboration. What happens next is that the scanner will pause on the frequency, flash the NAC for a second or so with no audio, then resume scanning. It will typically do this for a few seconds. I am suspicious that at these times the scanner has detected an encrypted transmission. I also monitor multiple nearby frequencies and never hear any continuation or response to the original hailing on any other frequencies.

So I'm suspicious the original hail is done in the clear, then the follow up response/conversation is carried out encrypted on the same channel. But that seems rather unnecessary (to have the hail in the clear), so I wonder if there are any other ideas to describe what I'm hearing...

 

[kb8q]

I monitor what is reported to be a Federal Law Enf frequency with my SDS200. I have it programmed as a digital frequency 167.3125 with NAC 167, I actually have the NAC set to "search".

Several times a day I will hear a short transmission, perfectly clear and legible, along the lines of "Base to John", or "Base to Cindy" or something like that. I never hear a response or any other clear transmissions, nor do I ever hear the hail repeated- its always a one time hail with no other information or elaboration. What happens next is that the scanner will pause on the frequency, flash the NAC for a second or so with no audio, then resume scanning. It will typically do this for a few seconds. I am suspicious that at these times the scanner has detected an encrypted transmission. I also monitor multiple nearby frequencies and never hear any continuation or response to the original hailing on any other frequencies.

So I'm suspicious the original hail is done in the clear, then the follow up response/conversation is carried out encrypted on the same channel. But that seems rather unnecessary (to have the hail in the clear), so I wonder if there are any other ideas to describe what I'm hearing...

It’s possible the mobiles are on a different frequency, or you’re out of range of the mobiles. Is it P25 conventional? You could try using a wildcard for the NAC like FFF and see if you hear the others.

 

[dave3825]

Several times a day I will hear a short transmission, perfectly clear and legible, along the lines of "Base to John", or "Base to Cindy" or something like that. I never hear a response or any other clear transmissions, nor do I ever hear the hail repeated- its always a one time hail with no other information or elaboration. What happens next is that the scanner will pause on the frequency, flash the NAC for a second or so with no audio, then resume scanning. It will typically do this for a few seconds. I am suspicious that at these times the scanner has detected an encrypted transmission.

Does the screen show enc or dat when its flashing the nac with no audio? What firmware is in the 200? Mine will briefly show enc if its encrypted. You could program the freq as P25 One Trunk which would, depending on your display settings, it can show radio id's that are tx'ing.

So I'm suspicious the original hail is done in the clear, then the follow up response/conversation is carried out encrypted on the same channel.

Without know the agency and freq, hard to give a definitive answer. Never heard a any federal agency calling people by first names. And like @kb8q said, they very well could be using 2 different freqs.

Do some research on the agency and see if there are any other freqs associated and enter those in and see what you get.

 

[richardbritt]

It's also possibly the input to a repeater and the station heard is just within range of his scanner. Write down the date and time and look for a pattern

 

[ecps92]

I monitor what is reported to be a Federal Law Enf frequency with my SDS200. I have it programmed as a digital frequency 167.3125 with NAC 167, I actually have the NAC set to "search".

Several times a day I will hear a short transmission, perfectly clear and legible, along the lines of "Base to John", or "Base to Cindy" or something like that. I never hear a response or any other clear transmissions, nor do I ever hear the hail repeated- its always a one time hail with no other information or elaboration. What happens next is that the scanner will pause on the frequency, flash the NAC for a second or so with no audio, then resume scanning. It will typically do this for a few seconds. I am suspicious that at these times the scanner has detected an encrypted transmission. I also monitor multiple nearby frequencies and never hear any continuation or response to the original hailing on any other frequencies.

So I'm suspicious the original hail is done in the clear, then the follow up response/conversation is carried out encrypted on the same channel. But that seems rather unnecessary (to have the hail in the clear), so I wonder if there are any other ideas to describe what I'm hearing...

Questions
Where in FLA? It could be the contracted Private Security handling the Gates at the Field Office. if the suspected $167 Agency
That said, there are other agencies who have been known to use $167, so it you can get some RID's that will help.

My Local FO who used PVT Security has a 167 Freq but is on $293 for the NAC, but the RIDs fall within the FO Ranges

 

[ecps92]

It's also possibly the input to a repeater and the station heard is just within range of his scanner. Write down the date and time and look for a pattern

if they are following NTIA rules, it would be either Simplex or the Repeater not an input.

Federal VHF/UHF Channel Plans - The RadioReference Wiki

wiki.radioreference.com

 

[merlin]

I picked up a radio that was likely a refgee from federal/Mil agencies. A LOT of USCG, DHS, federal, frequencies.
A good many repeater and P25 conventional frequencies, some set up with encryption keys. many different NACs.
I was going to ask about this myself. The wiki link posted by ecps92 outlines a lot of this.

 

[2wayfreq]

That looks like an FBI Channel and NAC.

 

[billy2047]

My local FBI, ICE and BP repeaters will often key up for data transmission for stuff like radio registration and authorization (Service Access Point SAP 32), encrypted user data (SAP 1) and SAP 41 encrypted key management message.

 

[ecps92]

Questions
Where in FLA? It could be the contracted Private Security handling the Gates at the Field Office. if the suspected $167 Agency
That said, there are other agencies who have been known to use $167, so it you can get some RID's that will help.

My Local FO who used PVT Security has a 167 Freq but is on $293 for the NAC, but the RIDs fall within the FO Ranges

still waiting on the OP to provide a more defined FLORIDA location, it's a rather large state.

 

[ecps92]

My local FBI, ICE and BP repeaters will often key up for data transmission for stuff like radio registration and authorization (Service Access Point SAP 32), encrypted user data (SAP 1) and SAP 41 encrypted key management message.

generally referenced as Vote-Scan

 

[dgoodson]

still waiting on the OP to provide a more defined FLORIDA location, it's a rather large state.

Leon county- supposedly an FBI frequency

 

[ecps92]

Leon county- supposedly an FBI frequency

Once you have some RIDs then it might validate the assumption, however that freq has been found used by other entities under DOJ

Your Field Office is over at Jacksonville, but there is an RA at Tallahassee

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