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Re: Topband: RFI

To: topband@contesting.com
Subject: Re: Topband: RFI
From: K4SAV <RadioXX@charter.net>
Date: Thu, 25 Jun 2020 14:02:24 -0500
List-post: <mailto:topband@contesting.com>
Power pole noise can be difficult to find with a portable receiver that is not directional. It's also difficult to find when all you have is an ultrasonic detector because those have to be pointed right at the source to hear anything.. Power lines make a good antenna for radiating power pole noise. Often the wires act like a long wire antenna and that can sent the noise for a long distance in the direction the line runs. My record for that with S9 noise at home on 160 has been 3 miles to the source. The source was very big.

To get started searching in the right direction try locating the direction with a rotatable antenna from home. A 6 meter Yagi does well usually. Then when you head off in the right direction, you need an AM receiver with a directional antenna, something like the MFJ-856 which is a 135 MHz AM receiver with a 3 element Yagi. That will get you within a pole or two. Other receivers can work too but it really needs to be on AM. Then an ultrasonic detector can be used to identify the part on the pole that is the source. I use a homebrew one but MFJ also makes one, the MFJ-5008.

After you think you have found the source, try to verify its characteristics with what you are hearing at home. You don't want to send the power company to fix something that is not your problem. I often find lots of noise sources that I don't hear at home.

Jerry, K4SAV

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