[SMCARA] METCOM 217 MHz interference

[Clarke, Tom AIR4.0P NATOPS]

Great detective work, Aaron!!
Looks like it could be a spur or possibly overload due to the minimum
freq separation.
Looks like somebody will have to QSY!
Thanks for the help.

Tom

Tom Clarke
Wyle Labs,  Aeronautics
NATOPS Program Support Specialist
USN/USMC National Airworthiness Office
Naval Air Systems Command, AIR-4.0P
(301) 995-3793/DSN 995-3793
Fax: (301) 757-6599
Cell (301) 904-2053
frederic.clarke at navy.mil


-----Original Message-----
From: smcara-bounces at mailman.qth.net
[mailto:smcara-bounces at mailman.qth.net] On Behalf Of Aaron Giles
Sent: Saturday, July 26, 2008 17:16
To: smcara at mailman.qth.net
Subject: [SMCARA] METCOM 217 MHz interference

I have been listening around the METCOM 217.825 MHz data frequency since

Tom mentioned their interference problem at the meeting on Thursday.  I 
have heard an occasional FM voice and FM/AFSK data transmitter about 
6.25 kHz below the METCOM freq.  Eventually I copied a CW ID from it, 
WQGF315.

Click on this link http://www.qsl.net/n8tvq/WQGF315.PNG to see the 
spectrum waterfall display.  I recorded this from a Uniden BC895XLT, 
with a tap I added to the 450 kHz IF.  I mix the IF down to 10.8 kHz and

then feed it into the computer sound card.  Then I use the DL4YHF 
Spectrum Laboratory software to look at it.  Along the center of the 
waterfall you see the METCOM transmitters.  The CW ID is visible 
approximately 6.25 kHz down from the center freq.

WQGF315 is an Automated Maritime Communications System (AMTS) license 
held by Maritime Communications/Land Mobile, LLC.  Click this link for 
the license info: 
http://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=2870470.  I

found this AMTS band plan on the FCC site: 
http://wireless.fcc.gov/auctions/data/bandplans/AMTS_band_plan.pdf.

I found this web page for the company, http://www.mclmllc.com/.  The 
coverage map on the web site 
(http://www.mclmllc.com/PassPort/Coverage/BaltimoreCoverageDec2004.htm) 
shows a site in Mechanicsville.  I haven't went mobile to see if this is

where the signal is really originating, but I think it's a good 
possibility.

Aaron Giles
N8TVQ


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