[RFI] Re: rfi-digest V1 #72

[James L. Keyes]

>     [RFI] Underground Power Cable RFI
> Date: Sat, 6 Jun 1998 08:55:19 -0400
> From: "N3GPU" <pelliott@flash.net>
> Subject: [RFI] Underground Power Cable RFI
> 
> When I come home in the evening I'm usually listening to a strong local AM
> broadcast station.  The spot where I park is directly over the underground
> power feed to the house.  During the past week or so, as I approach my
> parking spot, AM broadcast signals have been obliterated by high-pitched
> interference -- I'd say a raspy 1500 Hz or so.  I pull within literally 10
> feet of the parking spot before it starts.  I've also begun to notice it in
> my receivers on the low bands (160 and 80 especially) in the shack, about
> S7 so far.
> 
> All cable is buried for well over a mile.  The RFI is on the house side of
> the transformer.  The transformer is about 70 feet from the house and
> things are quiet there.  The problem is limited to about a 15-foot section
> starting about 10 feet away from the meter.  It's that isolated.  Things
> quiet down again as you get closer to the meter.
> 
> I plan to call the power company, but wondered if anyone among the
> assembled mind has experienced this type of underground-cable RFI, and has
> any suggestions on probable cause.
> 
> Thanks and 73,
> Paul Elliott N3GPU
> Westminster, Maryland USA
> The N3GPU Web Pages http://www.flash.net/~pelliott
> 
I used to do airfield facilities maintenance for the USN.
Our "leak detector" for the buried airfield lighting cables was a loop
antenna and AM receiver tuned to somewhere below 540KHZ.
The old cables often filled with water and malfunctioned for weeks
before finally shorting to ground and blowing out the circuit. You may
be experiencing something similar. Our detector was usually good enough
to get us within 5 feet of the actual problem.
Jim Keyes, WA1TQG/5

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