Mystery Control Channel

[N7YUO]

I came across this mystery CC today on 769.0875 from Kearns.
The signal is too weak for Unitrunker to decode.
I downloaded a list of all the 700 MHZ APCO frequencies and noted what UCA sites had those freqs.
I put all the frequencies in order in my WS1040 and locked out Nelson, Shawshank, N Salt Lake, Francis, & Mt Ogden.
Those are all the sites that I can receive now.
So scanning thru the remaining frequencies, I can search for additional sites.
Willow Peak is the only site that shows using 469.0875, but that site is far too distant to receive in Kearns.
FYI, I got my listing of UCA freqs from the Home Patrol Database that comes with Sentinel.
So all you sleuths see if you can get a read on this CC to find out what it is.

 

[Whiskey3JMC]

The signal is too weak for Unitrunker to decode.

So therefore no NAC to go along with that? Likely too far away to be Willow Peak...

 

[hazrat8990]

It's probably an image or birdie since that frequency isn't even licensed for use in the state. Have you tried to see if a scanner, or any other SDR software shows anything?

 

[kf7yn]

I came across this mystery CC today on 769.0875 from Kearns.
The signal is too weak for Unitrunker to decode.
I downloaded a list of all the 700 MHZ APCO frequencies and noted what UCA sites had those freqs.
I put all the frequencies in order in my WS1040 and locked out Nelson, Shawshank, N Salt Lake, Francis, & Mt Ogden.
Those are all the sites that I can receive now.
So scanning thru the remaining frequencies, I can search for additional sites.
Willow Peak is the only site that shows using 469.0875, but that site is far too distant to receive in Kearns.
FYI, I got my listing of UCA freqs from the Home Patrol Database that comes with Sentinel.
So all you sleuths see if you can get a read on this CC to find out what it is.

I'm not hearing anything on 769.0875 in West Jordan even with a pre-amp. I'm close to Mtn View Highway and 7800 South

 

[PMJ2kx]

That frequency doesn't comply with the 700Mhz public safety band plan. See here for more details. Only valid frequencies near that would be 769.08125 or 769.09375.

 

[N7YUO]

"That frequency doesn't comply with the 700Mhz public safety band plan. See here for more details. "
Only valid frequencies near that would be 769.08125 or 769.09375.
Both the RRDB and the Sentinel DB show 769.0875 as being assigned to Willow Peak
Just because it isn't in the band plan does not mean it isn't being used.
The Willow site near Moab shows some Low Power frequencies assigned as well as frequencies not in the band plan.
Part of the 700Mhz public safety band plan. *Willow Frequencies
769.00625 Low Power (Regional)
769.01875 Low Power (Regional)
769.02500* (Not in band plan)
769.03125 Low Power (Regional)
769.04375* Low Power (Regional)
769.05625* Low Power (Nationwide Itinerant) 7-US-01
769.06875 Low Power (Nationwide Itinerant) 7-US-02
769.08125 General Use
769.08750* (Not in band plan)
769.09375 General Use

 

[theaton]

That frequency occasionally shows up as a voice channel (never a control) on Willow Peak, but it may be an error.

 

[gldavis]

Check your bandwidth filter. I am receiving/decoding a control channel on 769.08125. NAC=815, control channel for System 014, Site 69.
Is this what you are hearing? (I love my 8600. It is great for this stuff )

 

[PMJ2kx]

So after doing some research, I'm wondering if it's actually 769.08125, and you're hearing timeslot 1, which would be 769.08125 + 6.25khz = 769.08750, but because it's such a weak signal, your setup isn't decoding it as a voice channel and you're only seeing/hearing the digital data stream?

Just a thought.

 

[gldavis]

Notice the word "Timeslot". P25 Phase II is a TDMA system. Time-Division Multiple Access. Transmissions still use the full 12.5K bandwidth, just half the time.

 

[nd5y]

Notice the word "Timeslot". P25 Phase II is a TDMA system. Time-Division Multiple Access. Transmissions still use the full 12.5K bandwidth, just half the time.

and the frequency doesn't change

 

[gldavis]

and the frequency doesn't change

Correct. The center freq stays the same. The real bandwidth stays the same (12.5k). "Slot 1" and 'Slot 2" indicate the Time Slot that is being used. This requires a very precise timing signal (GPS?) by all users. Since the signal is only there half the time, legally it is half the bandwidth. (Lawyers)

 

[maus92]

Channel 13 aka 769.0875 is a 25kHz "center" channel. It *might* be used as a HPD (High Performance Data) channel for in-car terminals. Fairly old use of the 700 PS band channels as LTE is preferred.

Edit:

Motorola ASTRO 25 HPD Air Interface - Signal Identification Wiki

Motorola's ASTRO 25 High Performance Data Air Interface allows Motorola ASTRO 25 HPD modems to transfer data at up to 96 kbps over a 25 kHz channel in the 700 MHz or 800 MHz bands.

www.sigidwiki.com