Two mystery Freqs in SoMD?

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Kumba

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Just goofing around with the scanner again, and randomly searching in the 408-409MHz range, I came across two frequencies that I didn't recognize. One might just be an ambient humming sound due to reception, but I'm not sure. The other one, 409.7375MHz, sounds like some kind of trunked control channel (motorboat sound) mixed in with some kind of pulsing beep. The static is bad enough that squelch kicks it, but always at fixed intervals, so I've got a sense this isn't just static, but a transmitter turning on/off to transmit whatever this is.

Thoughts? Files are linked below in MP3. 44100khz, 16bit, Mono original source; non-discriminator derived. I did a quick search on the FCC's sites for all freqs in this range, but nothing turned up.

http://drop.io/munc6d9
 

jim202

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Your 409 frequency is in the government segment. My bet is that it is one of the control channels
of the federal trunking system around the Capital Region. This system is in place for most of the
government facilities over a fairly large region. The radios used on the system are set up to run
on the system, no matter where they are. They search for the different control channels and
keep on playing. The talk groups are common to all the sites.

Jim




Just goofing around with the scanner again, and randomly searching in the 408-409MHz range, I came across two frequencies that I didn't recognize. One might just be an ambient humming sound due to reception, but I'm not sure. The other one, 409.7375MHz, sounds like some kind of trunked control channel (motorboat sound) mixed in with some kind of pulsing beep. The static is bad enough that squelch kicks it, but always at fixed intervals, so I've got a sense this isn't just static, but a transmitter turning on/off to transmit whatever this is.

Thoughts? Files are linked below in MP3. 44100khz, 16bit, Mono original source; non-discriminator derived. I did a quick search on the FCC's sites for all freqs in this range, but nothing turned up.

drop.io munc6d9
 

Kumba

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Indian Head, MD
Your 409 frequency is in the government segment. My bet is that it is one of the control channels
of the federal trunking system around the Capital Region. This system is in place for most of the
government facilities over a fairly large region. The radios used on the system are set up to run
on the system, no matter where they are. They search for the different control channels and
keep on playing. The talk groups are common to all the sites.

Jim
Yeah, I was wondering what system the control channel might resemble so I could plug it into my scanner and see if I could get enough of a signal to get a system ID from it. If it's LTR or EDACS, I probably would have to hunt down the remaining freqs in that range to determine the control.

The closest system I can find with freqs in that range is "Unidentified Federal System A73B::
http://www.radioreference.com/apps/db/?sid=3611

But that freq isn't listed at all on that system.
 

Kumba

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I think I found some kind of a ProVoice system on 952.4000. At least, that's what Unitracker thinks using the standard auio out port (my discriminator cable is packed in a box right now). Anyone ever run into that one before in the SoMD area? ~2-3 bars where I'm at.
 

Kumba

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I think I found some kind of a ProVoice system on 952.4000. At least, that's what Unitracker thinks using the standard auio out port (my discriminator cable is packed in a box right now). Anyone ever run into that one before in the SoMD area? ~2-3 bars where I'm at.
Found out what they were.

952.39375MHz is some kind of trunking control channel for SMECO (Southern Maryland Electric Cooperative). License is WNTT943:
ULS License - Microwave Industrial/Business Pool License - WNTT943 - SOUTHERN MARYLAND ELECTRIC COOPERATIVE INC

They also have some kind of beaconing frequency at 952.18125MHz, license WNTV357:
ULS License - Microwave Industrial/Business Pool License - WNTV357 - SOUTHERN MARYLAND ELECTRIC COOPERATIVE INC

It sounds like a Motorola trunking channel, but my scanner (BCD396T) refuses to let me program in 952.3937MHz as a control channel frequency for any of the Motorola options (except P25, but this isn't data I'm hearing).

I uploaded a sound sample at:
drop.io munc6d9

Is Unitrunker correct that this is a ProVoice system? The control channel sample linked in the wiki sounds nothing like it. This sounds more like some kind of Motorola Type II.
 

js_scan888

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There are some Multiple Address Systems (MAS) in the 952 Mhz range that sound like TRS control channels, but they are not. They just send monitoring data to other devices. I have also had Unitrunker falsely identify something as ProVoice when it wasn't. It wasn't even the same modulation as ProVoice, so there is something not correct with how the program determines the type of signal.

The 409.7375 freq is a ReFLEX signal, so you are just receiving an image. The real signal should be around 940.2625. If it's not that one, try searching between 940.0 and 940.5 for the real signal.

The 408.1875 freq sounds like interference noise to me.
 
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