Unidentified signal at 462.000 MHz

trossman

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Jun 17, 2020
Messages
22
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...

View attachment 96522
Hi Whiskey - thanks for taking a look. This is raw IQ data stored as a wav file. The way I open these is to set my SDR software (in my case SDR#) source to "IQ File (*.wav)" and then, once it loads, make sure to set the tuner to the frequency of interest - in this case 462.0 MHz. If its still not playing through your SDR software, maybe the file got jacked. Anyone else have success playing my IQ through their software?
 

trossman

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Jun 17, 2020
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Thanks everyone for considering this. I am pasting below what the FCC actually reports as active licensees with transmitters in my area. If someone is better than I at interpreting the jargon in here, maybe you can shed some more light than I could. To help narrow things down - can anyone identify the type of modulation being used in this signal?


Call Sign/Lease ID​
Name​
FRN​
Radio Service​
Status​
Expiration Date​
1WPDS307American Airlines Group, Inc.0022661201YGActive11/04/2023
2WPPY565COMMERCIAL COMMUNICATIONS INC0007403769IGActive03/15/2025
3WQAM227DOCTORS COMMUNITY HOSPITAL0010406270IGActive06/30/2024
4WQBC371Chevy Chase Club - Golf Maintenance0010932671IGActive09/17/2024
5WQQG710Howard Hughes Medical Institute-JFRC0020893574IGActive12/06/2022
6WQVL472Bear Communications, Inc.0004078838IGActive03/18/2025
7WSO555MILLS COMMUNICATIONS INC0002162352IGActive02/12/2023


If I had to guess, this seems to be coming from the direction of Tenleytown/AU, but RF is voodoo so who really knows (short of me driving over there with a kit).
 

jonwienke

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DHS has a facility next door to the NBC TV tower across Nebraska Avenue from AU.
 

freqhopping

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Lo Co VA/ FM19
What I've found is that I receive 462.0 better closer to DC in southernmost Montgomery Co. In my estimation, it's not originating from Tenleytown, too weak.
I don't receive it at all in Loudoun without using my roof antenna.

I don't receive 452.85 or 453.95 at all at the same MD location. In Loudoun I can recieve 452.85 and 453.95 on the duckie and really strongly with the roof antenna.

I don't get DCS codes on any of these.

The signal on 462.0 is different that the others. None of the VA licenses seem likely.

Montgomery Co KGC807 453.95 includes the emission type 10K0F1D which includes LTI Automated Vehicle Location (AVL) system - LT6 Radio Modem / LTI Automated Vehicle Location (AVL) system - LT6 Radio Modem.

452.85 WRE227 is also licensed by Montgomery Co but voice only.

Maybe these are some sort of tracking for Ride On buses, school buses and other county vehicles.
 
Last edited:

trossman

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Jun 17, 2020
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Thanks for running this down freqhopping. It was very helpful to have a second set of eyes from another point on the ground. So my best guess on 462.0 is Arlington, one of the FCC licenses WPPY565 (Commercial Communications Inc.) actually turns up on a fairly nearby transmitter. According to the license info, this station has four emission types on it, listed out below. Of these, the 462 MHz signal seems more consistent (at least to my amateur eyes) with a 7.6kHz bandwidth, and since I don't think its voice, my best guess (again, amateur/idiot here) is 7K60FXD 2-slot DMR (Motorola MOTOTRBO) TDMA data. DSD not helping. Still not sure about the 453.950 signal, but now that you mention AVL, I have seen similar looking UHF signals associated with WMATA's AVL system. Thanks again, let me know if you ever need me to check out a signal from here to return the favor.

11K2F2D--
Bandwidth: 11.2 kHz
Modulation Type: [F] Angle-modulated, straight FM
Modulation Nature: [2] Digital, with modulation
Information Type: [D] Data, telemetry, telecommand
Modulation Type Notes: F2D Data transmission by frequency modulation of a radio frequency carrier with an audio frequency FSK subcarrier. Often called AFSK/FM.
Emissions Designator Notes: 11K2F2D Audio frequency shift keying within a 12.5 kHz channelspace (commonly used for 1.2 kbps packet, FFSK station alerting, and AFSK tornado siren signaling)


11K2F3E--
Bandwidth: 11.2 kHz
Modulation Type: [F] Angle-modulated, straight FM
Modulation Nature: [3] Single analog channel
Information Type: [E] Telephony, voice, sound broadcasting
Modulation Type Notes: F3E FM speech communication – often used for marine radio and many other VHF communications


7K60FXD--
Bandwidth: 7.60 kHz
Modulation Type: [F] Angle-modulated, straight FM
Modulation Nature: [X] Unknown
Information Type: [D] Data, telemetry, telecommand
Emissions Designator Notes: 7K60FXD 2-slot DMR (Motorola MOTOTRBO) TDMA data


7K60FXE--
Bandwidth: 7.60 kHz
Modulation Type: [F] Angle-modulated, straight FM
Modulation Nature: [X] Unknown
Information Type: [E] Telephony, voice, sound broadcasting
Emissions Designator Notes: 7K60FXE 2-slot DMR (Motorola MOTOTRBO) TDMA voice
 
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