[Lowfer] Frozen trees ??

[rick kirby]

Thanks  Jay, Doug and John ,

 Jay;
  your hypothesis seems to be right in line with what is taking place here
at my QTH. I probably get a bigger change with short warm spells than you
because the trees are taller than and much closer  to my antenna. Last month
I borrowed your matching transformer idea after visiting your website.I am
using a CRT flyback core though because I had a few lying around and wasn't
worried about heat loss. It worked out much better than grounding the
loading coil directly and tapping for a match. I will see what happens in
the spring when the sap starts to flow again .
 Doug;
 I wish I had the time to experiment. I would move my antenna all over the
lot and see just what happens at different distances .Maybe someday after
retirement!
 
 John;
There is no change in resonance. I have fiddled around with the variometer
and the final still likes it right where it is. My trees are all oak and all
within 25 feet of my top hat. Two trees support the antenna with 15 to 20
feet of line and  6000 volt rubber insulators in between. The only
capacitance change I noticed was when the leaves fell  off.  I do know this;
this antenna shouldn't be working as well as it has been. Doug  was able 
to copy me at almost 500 miles when the temperature was in the teens....and
that's where I hope it stays till spring.

 73 and thanks for the input !!
Rick  KA2PBO



-----Original Message-----
From: lowfer-bounces at mailman.qth.net [mailto:lowfer-bounces at mailman.qth.net]
On Behalf Of JD
Sent: Monday, January 07, 2013 07:40
To: Discussion of the Lowfer (US, European, & UK) and MedFer bands
Subject: Re: [Lowfer] Frozen trees ??

>>> Everything I have read tells me I should lose current when temps are 
>>> freezing but I don't think my ground is a factor.

Goes to show you can't believe everything you read! :)

Seriously, not all soils behave the same under differing temperature and
moisture content.  What happens at one location is not necessarily what will
happen at another, either in terms of loss resistance or capacitance between
antenna and ground.  However, I'm inclined to agree with you that your
ground system may not be changing all that much in the circumstances you
describe.

(Just for reference, when you "lose current," is that even after retuning of
your inductor?  And is there a pattern as to whether colder temperatures
require more or less inductance?  I'm wondering whether the changes you
experience are strictly a change in resistance, or in antenna capacitance,
or both.)

Your tree sap hypothesis is quite plausible!  As I think I mentioned in a
previous LW Message Board thread where we were talking about tree-supported
LowFER antennas, my experiences in Georgia led me to believe the same thing.

Where deciduous trees could be used to support an antenna, there was a
distinct difference in efficiency between summer (totally lousy) and winter
(merely poor).  But with pines or other evergreens, the loss was there all
the time, except maybe during the very coldest of weather...and I couldn't
even be too sure about an improvement, because at best the signal was so
poor it was never copied more than a county or two away.  That would be
consistent with tree sap as a loss factor.

I'd almost be tempted to suggest a Faraday shield for the trees.  I did
something like that at a radio station once, though it was more for
lightning secondary-discharge protection of a satellite dish than for RF
reasons.  But it did seem to reduce the amount of RF current in the trees. 
There's almost no chance of it being practical where the tree is one of the
supports for the antenna, though.

John
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