Unidentified signal at 462.000 MHz

trossman

Member
Joined
Jun 17, 2020
Messages
22
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

More Info Coming Soon!
Premium Subscriber
Joined
Jul 18, 2014
Messages
13,460
Location
VA
It's not GMRS, by definition. It's not on an approved GMRS frequency, and continuous transmission isn't allowed, either.
 

Delta2_Coms

Member
Joined
Dec 15, 2020
Messages
6
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

Member
Joined
Jul 8, 2002
Messages
12,053
Location
Taxachusetts
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!
 
  • Like
Reactions: wtp

trentbob

W3BUX- Bucks County, PA
Premium Subscriber
Joined
Feb 22, 2007
Messages
3,258
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

Member
Joined
Jul 8, 2002
Messages
12,053
Location
Taxachusetts
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

Member
Joined
Jun 17, 2020
Messages
22
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

Member
Premium Subscriber
Joined
Jun 27, 2019
Messages
174
Location
Garden Grove, CA
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

Member
Joined
Jun 17, 2020
Messages
22
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

Member
Joined
Jun 17, 2020
Messages
22
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

Avid surfer...of the AIRWAVES!
Premium Subscriber
Joined
Jul 16, 2006
Messages
2,394
Location
Montco, PA, USA
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
 

Cameron314

Member
Premium Subscriber
Joined
May 30, 2003
Messages
143
They have licenses for the DC area. I have no reason to accept what you say. Provide evidence please. Thanks.
Nether of the two licenses are for the DC area. Rohm and Haas is for PA and Chevron is for LA.
 
Top