Many years ago W7EL wrote a comment about tree sucking RF; he thought it
was important but never followed thru with a study that I am aware of.
Dont confuse with Tree Hugging Wackos.
My own expeiments on 80M in 1983 showed that I had to have the vertical
wire at least 6' from a pine tree trunk in order to obtain reasonance at
the "predicted" length. The final result was a 6 wire cage hung at the
limit I could safely support with a 10' RS mast strapped to a branch.
Results were good enough to prompt me to hang a second cage from another
pine with 1/4 wave antenna spacing. The DX performance was outstanding
and it was the antenna I used to set the multiplier record as a 80M
single band entry in ARRL DX CW in 1985 or 86. Forget the year but W1FV
beat me on Q's !! I believe that record may still hold.
In any case I used those tree verticals to cfm about 260 DXCC on 80M
before moving across town in 1990.
I cant speak for redwoods, etc but I will warrant a guess that the tree
absorbtion becomes a small percentage after about 6' or so on 80M.
Double that or halve it on 160??? Maybe W3LPL or others with access
to the higher levels of NEC can provide a hint.
GL.............Carl
07:24:29 -0800 (PST) Ward Silver <hwardsil@wolfenet.com> writes:
>
>Aside from bad puns about trunk lines and branch circuits...
>
>My inverted-L relies on a stout redwood (these aren't trees, they're
>wooden pyramids) to support the vertical wire. At the feed point, the
>wire, coax, and radials are within 6" of the tree. What is the wisdom
>of
>this august body (even if it *is* December) about the RF-absorbing
>properties of trees at 160-meters? I'm going to pull the feedpoint a
>little farther away from the tree, but it will still be a tiny
>fraction of
>a wavelength away.
>
>73, Ward N0AX
>
>
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|