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[RFI] 30m Interference

To: <rfi@contesting.com>
Subject: [RFI] 30m Interference
From: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 30 May 2011 07:19:17 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Looking for clues concerning interference to the 30m band being caused by 
what appears to be two digitally-modulated transmissions, one exactly at 
9955 kHz and the other at 9965 kHz.  The peak amplitude changes little with 
changes in propagation, leading me to believe it is local, but I have 
validated that the source is not in the immediate area of my QTH.

Looking at the print-screen, you will see the WWV carrier which does change 
substantially in amplitude with varying QSB conditions.  The amplitude of 
the two interfering transmissions does slowly change over the long term. 
For example, they are weak in the early morning, then rising during the 
daylight hours.  But again, they are not subject to QSB.

http://72.52.250.47/images/RF-Noise-053011-1.JPG

I would like feedback on the following.  You may wish to reply directly to 
me:

1) Can you see these transmissions at your QTH?

2) Any idea as to the type of modulation being used based on the spectra?

Many Tnx!

Paul, W9AC 

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