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January 28th 05, 05:25 PM

On Fri, 28 Jan 2005 12:24:13 -0500, Buck wrote:

On 28 Jan 2005 04:38:01 -0800, wrote:

M. van Wijk (incl) wrote:
Hello,

I just moved to a new location. My backyard has some 20 trees spread
around
at a distance of 5 to max 10mtrs between each of them.
I would like to opt for a full size 40mtr(7Mhz) vertical and have
(only)the
2 following options her:

1) full size 1/4 wire vertical inside fishing pole, mounted in a tree
at a
foot height between 7 and 10mtrs from ground level. Some 4 elevated
radials
will be added.

2) full size 1/4 wire vertical at ground level, parallel to a tree at
a
distance of 0.5 till max 1 mtr. Ground screen will be some 16 pcs of
wire
buried in the surrounding ground.

I have no clue about any effects of trees here. They are not pine
trees.
There are lots of other parameters in the whole picture, but the
trees is a
totally unkown factor for me.

Please share me your experiences.

Thanks in advance.

You might consider a simple inverted L given all the trees you have
available. Build a very conventional half-wave coax-fed 40M dipole.
Suspend half of it (35 feet long?) vertically with the lower end a foot
or two above the ground from one tree then pull the other half more or
less horizontally to another tree. Pull the coax away from the elevated
feedpoint toward the Radio Room. Trim wires to resonance. No messy
radials needed and most likely you wouldn't need a tuner or "tuning
network" either. It would be just a standard inverted vee rotated 45º.
Half-wave inverted Ls without radials scream, been there, done 'em.

Research on the subject done by the U.S. Army years ago determined that
trees have no measurable effects on HF antennas. Trees do have an
effect on vhf/uhf antennas. There was a thread in this NG in the past
which addressed the topic in sdome detail and which is probably still
archived. Run a search on "Do Trees Absorb RF?"

'73 Mark, PA5MW

w3rv

Since he has room to hang a vertical, he can hang a slanted dipole
too. That would be a little directional but pointed in the right
direction it could be a great antenna.

OOPS! forget my last....

(remember to engage brain before fingers.)
--
Buck
N4PGW

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