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Re: [TowerTalk] Corona Electromagnetic Interference

To: "Barry Merrill, W5GN" <>
Subject: Re: [TowerTalk] Corona Electromagnetic Interference
From: Kipton Moravec <>
Date: Sun, 24 Apr 2011 22:58:32 -0500
List-post: <">>
On Sun, 2011-04-24 at 19:42 -0500, Barry Merrill, W5GN wrote:
> I'm really confused.   This is an FM repeater, so the noise is capturing the
> receiver,
> turning on the repeater, and you hear all the noise, only when it's raining?

No. The nois is bad when someone wants to use the repeater. Mobile
stations as so noisy they are hard to understand. One of the NCS usually
has full quieting at 25W had to go to 75W to be understood.

When there are not storms nearby everything is fine, and we get 50-60
mile range to mobile stations. It goes away quickly when the storms
pass.  The storm may or may not have rain at the repeater.

We do not think it is a moisture problem because it clears up before
things have a chance to dry up.

> Or, the noise never captures the receiver you only hear noise when a station
> has
> captured the rf and turned on the repeater and then you hear lots of noise?


> I know from submerged operations from Navy Submarines that if this were 10
> meters
> SSB or CW, it sounds like rain static and you only need a high ohm resistor
> from the antenna to ground.
> Barry, W5GN

That is what I am wondering about. Using a 1M to 10M resistor from the
center conductor to the ground, to bleed off any static. That high of a
resistance would not affect operation.


> -----Original Message-----
> From:
> [] On Behalf Of Kipton Moravec
> Sent: Sunday, April 24, 2011 6:27 PM
> To: Fuqua, Bill L
> Cc:
> Subject: Re: [TowerTalk] Corona Electromagnetic Interference
> On Sun, 2011-04-24 at 01:59 -0400, Fuqua, Bill L wrote:
> > If you have not had a problem in 4 years and now you do you may look into
> other electrical hardware on the tower.
> > It may me lighting systems that have started to arc when there is 
> > heavy rain or some other electrical problems caused by rain or wind.
> > If it is particularly cold it could be ice on the antenna which detunes
> it. Water has a very high dielectric constant.
> > Unlikely corona. 
> > 
> > 73
> > bill wa4lav
> > 
> When we inspected the system yesterday, we noticed none of the antennas were
> properly grounded to the tower where they clamped onto the upright of the
> railing around the top of the tower. 
> The railing has a heavy coat of paint, and I guess that we assumed that the
> U-Bolts would crush the paint and make contact. If they do not then that is
> like a capacitor. In the next couple of weeks we are going back and adding a
> short #8 or #10 ground wire from the antenna to a self-tapping screw into
> the post where we are certain we will be making good electrical contact. 
> We have lightning arrestors where the coax goes into the the tower, and
> there is a big copper grounding plate. 
> About halfway down there is a grounding strap from the coax shield to one of
> the water tank ground wires. 
> At the bottom, the coax shield is grounded again to a big single point
> ground near the repeater cabinets. 
> So we have identified one potential problem area. But it still baffles me
> why we have not had a problem until this spring. And it is bad when a storm
> comes through and clears up quickly when it passes. Not very good for a
> Skywarn repeater. But that tells us that it is not a moisture problem,
> because it would take a long time to dry out. That is not the case.
> Our "lightning arrestor" experts tell us that the lightning arrestor will
> fail in a short between the center and coax shield, so it is not the
> lightning arrestor. That seems a little odd to me, but he works on
> commercial antenna sites as his job, and is very knowledgeable. So I have to
> believe he knows what he is talking about. 
> We are in North Texas, and do not currently have any ice to worry about.
> We do get ice storms for a couple of days in the year, but not now.
> Thanks for the suggestions everybody.
> Kip
> --
> Kipton Moravec AE5IB .- . ..... .. -...
> "Always do right; this will gratify some people and astonish the rest."
> --Mark Twain
> _______________________________________________
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Kipton Moravec AE5IB .- . ..... .. -...

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


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