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[TowerTalk] Corona Electromagnetic Interference

Subject: [TowerTalk] Corona Electromagnetic Interference
From: Kipton Moravec <>
Date: Fri, 22 Apr 2011 21:11:39 -0500
List-post: <">>
Our repeater antenna is located on a 180 foot water tower. 

We have not had a problem in the 4 years it has been up there. It is
used for Skywarn nets when we have bad weather in the county. 

The past two storms this year the noise was so bad it was hard to hear
the mobile stations, and even the NCS who is normally full quieting at
20W had to increase his power to 75W on 2M to be heard.

The noise seemed to happen when the storms were around and cleared up
once they passed. It seemed constant not the crackle from lightning.

Someone who knows a lot more than me said it was Corona. 

This is a 1.5M gallon water tank. It has a 18" pipe with a column of
water going to ground. There are at least 8 braided ground wires from
the tank to the ground spread evenly down the concrete support. 

We have a 270 foot 1 5/8" coax going from the base to the tip side of
the  tower. The VHF repeater where we seem to be having the most
noticeable problem has a Decibel Products antenna (with a grounded mast
and 4 loop elements on the side each 90 degrees apart and a matching
harness). We have one for the 2M repeater and one for the 70cm repeater
both using the same coax coming up the tower and splitting with a
diplexer to the two antennas on the top of the tower.

Hopefully there is enough background information on what we have.

What can we do about the corona EMI? 
How do we get rid of it? 
Why are we just noticing it this season, and not before? 
Could something be going bad? What?

We are going to be checking the site in the morning. What should I be
looking for?

Kipton Moravec AE5IB .- . ..... .. -...

"Always do right; this will gratify some people and astonish the rest."
--Mark Twain


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