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LF: Re: Measuring resistance of aerial system

To: [email protected]
Subject: LF: Re: Measuring resistance of aerial system
From: "Vernall" <[email protected]>
Date: Mon, 26 Feb 2001 07:36:57 +1300
References: <001a01c09e42$95b26320$cb9e74d5@w8k3f0>
Reply-to: [email protected]
Sender: <[email protected]>
Dick PA0SE,
 
Regarding your observed losses being higher in damp conditions:
 
It amazes me that the resistance is lower in summer than in winter. I had expected the opposite.
There are no trees near the aerial.
 
When it rains or in fog the resistance rises considirable, as indicates by the aerial current dropping by up to 25%.
 
Could that be due to water particles being heated in the field around the aerial? Or is it only caused by increased leakage via the aerial insulators and the feed-in? 
 
You could check for leakage on the antenna wire with a "megger".  You may also have induced losses in the wall of your house and loss happens to vary with moisture conditions (could be checked before and after a hosing down).  A possible countermeasure is to increase the spacing of the antenna "upwire" from other objects (which reduces the field strength and induction loss in the other surface?).
 
73, Bob
 
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