Hi Johan, I reckon you can make a fairly good guess at that even without
Jim's measurements. Ideally the end of the top wire needs to be as far from
the top of the tree as it is from the ground, so that the majority of the
current induced by the high voltage at the end of the top wire, goes to
ground. The negative point is this means shortening the run of the top wire,
but you can bend it at 90 degrees and turn it into a flat "T" shape if you
have enough trees. The direction of top load is not important because it
does not radiate significantly, but it does contribute to reduced ground
loss.
Going back to some experiments that Mike Denisson G3XDV did many years ago
now....he grounded his house-mounted support pole. This increased his aerial
current and increased the signal. The gress was that this made a less lossy
path for the coupled current. One would expect the antenna current to
increse but since it was being "taken out" of the vertical and shunted to
ground one would not have expected a significant increase in field strength.
So the next question is what happens if you make the tree "a good conductor"
by dropping a wire down its trunk ?? This now begins to look like a
configuaration that Rik proposed a number of years back but I believe did
not have the time to test.
This is the fun of LF you can ask "silly" questions like this !! and have
fun exploring then cos it ain't in the books !!
Oh and, Yes it is reciprocal, but might be fun to try and match to !!
Well done Jim, nice experiment.
Cheers de Alan
----- Original Message -----
From: Johan H. Bodin <[email protected]>
To: <[email protected]>
Sent: 12 June 2007 12:08
Subject: Re: LF: Tree current
> Jim, the LF group,
>
> thanks for sharing a very interesting experiment!
>
>
> James Moritz wrote:
> > Generally, trees closer to the antenna and with
> > bigger areas of foliage had higher currents, as you would expect.
>
> This raises the following question:
> http://web.telia.com/~u33233109/
>
> I bet the answer contains the words "it depends..." ;-)
>
>
> 73
> Johan SM6LKM
>
>
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