Dielectric loading can have profound affects. I wondered if it could be
that early on in the thread, but I've never experienced it (that I know
of) in rain. However, it takes very little ice to detune my KT-34A. My
40-CD2 is less sensitive, but is certainly affected. My 80 M inverted V
is unaffected by rain, but 1/4" of ice really moved it's resonant
frequency down a lot. All antennas feed impedance is also altered even
at resonance, so it's not merely a change in resonant frequency.
Kim N5OP
On 4/13/2016 12:30 PM, Charles Farr wrote:
I have noted similar changes on my KT-34XA. I've heard that on these
antennas that water gets into the capacitors on the elements, causing
the tuning to change. It doesn't last very long after the rain stops.
Just something I live with when it happens. SWR that is normally 1.5:1
or less rises to 2 - 2.5. I also experience a lot of precipitation
static when it rains, snows, etc. I've also heard these effects are
less on yagi antennas of "plumber's delight" construction. Just
observations, no real tests, or science.
73
Chuck, W6AJW
On 04/13/2016 07:38 AM, john@kk9a.com wrote:
I was thinking the same thing. My homebrew antennas have flat SWR well
below and above the band edges and I have not noticed any change on my
LP-100A's display when it rains.
John KK9A
To: towertalk@contesting.com
Subject: Re: [TowerTalk] frustrating rain and connections... update
From: "Joe Subich, W4TV" <lists@subich.com>
Date: Wed, 13 Apr 2016 08:23:51 -0400
On 4/13/2016 12:09 AM, Bob K6UJ wrote:
I have always noticed a slight change in the swr with hf yagis when
it is raining. Just a minimal change though. Nothing like what Gary,
K9RX reported.
One would expect that the amount of "detuning" would be related to the
overall "Q" of the antenna. Antenna designs with critical element
tuning - particularly DE/D1 - will detune more than designs optimized
for lower frequency sensitivity (OWA, log-cell, etc.).
The KLM/M2 designs have always been rather "fiddly" when it comes to
tuning/SWR - specially when compared to some newer designs like the
OWA, LFA, etc.
73,
... Joe, W4TV
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--
Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
/"In theory there is no difference between theory and practice. But, in
practice, there is." //– Attributed to many people; it’s so true that it
doesn’t matter who said it./
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