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Re: [RFI] Six Meter Intruder

To: "Johnson, Karin" <Karin.Johnson@nielsen.com>
Subject: Re: [RFI] Six Meter Intruder
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Tue, 02 Mar 2010 15:49:49 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
A few guesses:
Many older devices use Ch 2 and Ch 3 to feed the TV set. It's possible 
some one decided they needed a third link and managed to twiddle the 
frequency down into 6-meters, or a component failed shifting one down.  
Remember too that the cordless devices operated just below six.  I don't 
know if any of those monitors used TV or not.

Probably the most likely possibility is the cable system. They have 
stuff all over the place and it doesn't take much for a substantial 
signal to leak out. IIRC around here they do have something on what 
would have been channel one and of course cable channel 18 is right in 
the middle of 2-meters. Just listen to 145.25 for leaks.

 It's also possible there's some mixing going on somewhere with the 
resultant coming out in the six meter band.  We had that happen to our 
local repeater. We received a report of interfering with a public safety 
system, but the system was well beyond our coverage range.  It turned 
out there was either a police or fire repeater about 30 or 40 miles from 
us (and of course much closer to system suffering interference).  They 
had a device go non linear and mix our signal with another.  The 
resultant was our freshly amplified image was right on the input to the 
system suffering the problem.

 73 and good luck,

Roger (K8RI)

Johnson, Karin wrote:
>   Hello Group:
> Recently while investigating a noise source on 15 meters I had my
> spectrum analyzer hooked up to the antenna and noticed a few very strong
> carriers up around 50 MHz.  I'm not active on Six Meters so wasn't too
> concerned about them, but my curiousity got the best of me and I took
> out the VX-5r and tuned to one of them at 50.650 MHz.  To my surprise I
> was hearing television audio and distinctly noticed an NTSC video
> carrier 4.5 MHz lower in frequency.  Now this is not normal.  I went for
> a brief walk to see if the signal either increased or decreased in
> amplitude.  I couldn't see a major change in signal strength by walking
> only a few houses away (about 300 feet). I did turn off the main power
> to my house, so it isn't coming from some unknown device in my house,
> like a cable set top box gone rogue. 
> My question to the group is, has anyone come across a new breed of
> television extension device like some that Radio Shack sell for remoting
> a video/audio feed via 2.4 GHz link.   Only this one functions on or
> near the six meter band?   Just a curious question at this point.  As I
> mentioned before I don't operate on six meters so is really no concern
> to me.   
> Karin Anne Johnson  P.E.  K3UU
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