Unidentified signal at 462.000 MHz

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trossman

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Hello -

I have been detecting a continuous signal at exactly 462.000 MHz. While initially I thought this was GMRS, the GMRS channel plan starts at 462.5625 MHz, and does not appear to include 462 on the nose. I am able to pull DCS codes from the signal, however, they are non-standard codes +037 +137, -057 -172. The signal does not seem to be loaded with any audio as far as I can tell. FCC search turns up a few candidate licensees and locations, of which a few are consistent with a directional antenna sweep I did. No further info provided in the FCC database, unfortunately.

Any thoughts on whether this is GMRS, or how I can explore this further? Screenshot below, raw IQ available upon request. Thanks!

Capture2.PNG
 

jonwienke

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It's not GMRS, by definition. It's not on an approved GMRS frequency, and continuous transmission isn't allowed, either.
 

Delta2_Coms

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My best guess is that it seems to be a data transmission.

462 MHz is in a frequency range allocated to either federal government space-to-earth communications, or "private land mobile" (commercially licensed) use. If it is used for satellite telemetry/data, then the data will use some sort of encryption and I wouldn't expect audio to be part of it.

-All the best
 

ecps92

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GMRS is 462.5500 - 462.7250 / 467.5500 - 467.7250

What you likely have is Business Band [FCC Part 90]

Hello -

I have been detecting a continuous signal at exactly 462.000 MHz. While initially I thought this was GMRS, the GMRS channel plan starts at 462.5625 MHz, and does not appear to include 462 on the nose. I am able to pull DCS codes from the signal, however, they are non-standard codes +037 +137, -057 -172. The signal does not seem to be loaded with any audio as far as I can tell. FCC search turns up a few candidate licensees and locations, of which a few are consistent with a directional antenna sweep I did. No further info provided in the FCC database, unfortunately.

Any thoughts on whether this is GMRS, or how I can explore this further? Screenshot below, raw IQ available upon request. Thanks!
 
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trentbob

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In my area, that frequency was our counties EMA frequency and with a different PL tone it was also used by fire photographer Buffs.
 

ecps92

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Likely a Commercial Rental Repeater, look for any names that might be associated with a Radio Shop or Shop Name.
DC you would/could possibly hear DC, DE, MD, VA for licensees

there are a few under MD and VA that standout - Bear Comm, Commercial Communiications, Mills Communications - right off the top
Especially when you are seeing multiple CTCSS and/or DCS tones appearing.

I am in the Washington DC area.
 

trossman

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Actually, I am seeing a very similar signal on a few different frequencies nearby. In addition to 462.0 MHz, I detected similar on:

~452.850 MHz (possibly two of them very close to each other at 452.84875 and 452.8516, transmitting complementary to each other).
~453.9495 MHz (also looks like two signal structures spaced closed together).

452.852.PNG 453.949.PNG

Finally, here is a link to a raw file at 462 MHz (the strongest of these) in case anyone feels like joining me in this rabbit hole. Also, I may take this to another thread, since its not GMRS - apologies and thanks all for your time.

PS - I also thought maybe MOBITEX, but I don't think they use UHF bands in the US, and it won't decode in PDW (for what its worth).
 

Randyk4661

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Is DSD+ coming up with any trunking information? First thought this is a control channel for trunking. Second thought this is a telemetry signal.
 

trossman

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Is DSD+ coming up with any trunking information? First thought this is a control channel for trunking. Second thought this is a telemetry signal.

Unfortunately DSD comes up short. Not even a whiff of anything it can normally decode. I see plenty of other control channels in this band for DMR and P25, but that doesn't seem to be this.
 

trossman

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If anyone feels like peeling this onion in the Washington DC metro area:

There's a continuous signal at 462.000 MHz which I can't for the life of me figure out what its for, or who is using it. It's 462 MHz on the nose (so its not GMRS). DSD+, PDW, and other software I have doesn't do much for me (i.e. doesn't appear to be DMR, P25, POCSAG, etc.). Best I can do is pull out some DCS codes from it, some of which have been non-standard. I see similar but weaker signals at 452.850 and 453.949 MHz, as well. FCC license search hasn't narrowed it down for me, other than showing a few entities who use 462.0 MHz, but its short on detail otherwise. Best guess on the 462.000 MHz signal is that its coming from the towers at Tenleytown/AU (based on a 360 sweep with my yagi), but again, the FCC info for those towers wasn't of much help there.

Screenshot below, and here's a link to some raw IQ. Welcome insights!

Capture2.PNG
 

Whiskey3JMC

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I listened to the audio file and I'm not hearing anything other than the noise floor hiss. I brought it up on Audacity and am seeing tiny deviations on the wave form but nothing I can easily identify...

1609799203691.png
 

maus92

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They have licenses for the DC area. I have no reason to accept what you say. Provide evidence please. Thanks.
It's simply a matter of understanding what the FCC data is saying - while the licensee contact addresses are in DC, the transmit locations are not.
 
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