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G8MNY > TECH 05.03.17 14:29l 173 Lines 7658 Bytes #-3196 (0) @ WW
BID : 127FC2MAC
Read: DK3UZ GUEST DF7EAV
Subj: Tree Antenna Sky Hooks
Path: DB0FHN<DB0PM<OE5XBL<F1OYP<SR1BSZ<IR2UBX<IK8VKW<F1OYP<FAQI<F1MAC<
F1OYP<N9PMO<I0OJJ<GB7CIP
Sent: 170304/1009Z @:GB7CIP.#32.GBR.EURO #:37064 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jul 09)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
There are several ways to put a rope in a tree...
BOW & ARROW
The normal arrow is too light to pull up much so adding a weight to the point
will greatly help, suitable are a layer or two of Pb solder/steel/Cu wire
tightly wound on to double or treble the weight of the arrow.
No ,,,,,,,, /////////
Point (°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°³°°°°°°°°°°°°[
'''''''' \ \\\\\\\\\
Weight `\ Thin string or
`-._ Fishing line
No point is needed, as there is a danger it could hit someone or get stuck firm
in the tree bark. Attach a thin string or thin fishing line to the rear of the
arrow. Estimate how much line is needed to do the shot & unravel that amount in
neatly & untangled front of you, if ground is too rough spread it out on a
tarpaulin etc. When placing the arrow in the bow make sure there is no risk of
line entanglement with you or the bow.
What to aim for.
/'~`\ \/ \/
.-'~`ú. L A R G E \ Tree \\// `\
/ TREE `\ T R E E \ Branch// `\
|| `\ Aim | | |Aim || `\Aim
1/ Aim shot to either clear the whole tree, if you can get to the other side.
2/ Or aim much steeper, to fall into the top of the tree so that line falls
through middle of tree canopy,
3/ Or over a suitable branch if your aim is good.
Done in the winter with no foliage, you can see far more of what you are doing.
N.B. Thick foliage also grabs the line making the arrow difficult to free up so
that gravity does the work.
CATAPULT
This is much the same as for the bow & arrow, but you must use thin fishing
line, then pull over a thicker line. The shot weights (tear drop shaped or just
cubes of lead (10-15mm sides) with a hole drilled through it, are small & not
very visible, so use brightly coloured ones e.g. Orange/Red not green/yellow/
brown, as this will help spotters the other side of the tree to see the shot.
As with bow & arrow a heavier weight is need if there is sticky leaves or soft
bark that "grab methods your strength timing & skill are more important.
Make sure the line is going to pay out freely & that you are not going to get
entangled.
I have put lines into trees at a good 18M with this method. Due to the heavier
weight, the tree grabbing problem of the line is less, except for miss fires
where the shot has to be pulled from the wrong branch etc. In that case beware
of knotting the cord around a branch!
Often a high shot is best coming down in the tree especially if you can't
reach the other side of the tree!
BACK THROW
Bob VK6BE reminded me there is another method, & that is to stand with your
back to the tree & lift a stone in a short line/sling (he suggest a long sock).
.ú .
M E D I U M .
S I Z E D .
T R E E .
|| .
|| O .
|| Ý\\ ,
|| ./\./ú
You effectively turn yourself into a Trebuchet machine. There is a mechanical
advantage to this method, as both arms are used & the sling length speeds up
the shot. Bob says 60ft can be reached my this method.
TALL POLE METHOD
This is a non ballistic method. I use 17m of very thin set of telescoping
poles. e.g. poles of 1.25" 1.5" 1.75" & 2" with matching size U exhaust clamps
done up over the joins, so that the U is only over the thinner pole & the clamp
over the larger one.
U ³ Ý clamp
\ ³ Ý_/
(ðððððððð__³]ð NUTS
³5øAngle ³Pole
³pole cut³higher
³ ³
The top pole then has a Y shaped twig put in it, to take string over the top.
/Y\ |Y\
M E D I U M | ³ | M E D I U|³M\
S I Z E D | º | S I Z E |Dº \
T R E E | Þ | T R E E| Þ \
|| | ³³| || | ³³ \
|| Weight 0 ³³| || 0 ³³ \
Extend the pole set on the ground (do clamps up as needed) to be taller than
the wanted anchor point in the tree. Tie a hefty weight (half brick) to the
string & put a long loop of the string over the top pole Y.
Walk up the fragile set of poles with someone footing the base keeping it on
the ground. Carefully position the whole pole against your target point in or
above the tree.
Pull on the free end string to raise the weight to the top. When it is over a
suitable branch, lower the weight. With careful jigging the weight should
come down OK through the tree branches. Avoid knotting it around branches if
recovering for a 2nd attempt!
HALYARDS
For permanent locations it is desirable to have halyards at each end of HF wire
aerials so that they can be lowered for maintenance & tuning up the aerial etc.
A simple mostly enclosed galvanised cast pulley that has a crude steel pin
bearing well need to be greased. (e.g. hot runny greasote the initial pull up rope will soon be overgrown into the tree bark & the
pulley will not be recoverable after a few years.
INSULATORS
For fair Wx /P activity end insulators are not needed as dry string, nylon, or
polyprop, are all excellent insulators at ham QRP levels (<1kW). But in
permanent & for wet conditions good insulators are needed as arcing/losses
could occur, especially in coastal sea spray areas.
.===-.. ... =:\
/ _ `\\. /'_ """\\\
==////=======) ³ >>\\\\\==== ======/////===) ³ >>\\\\\=======
\ " .// \ " __.///
`====:' `""" =:/
R I G H T W R O N G
Black plastic egg insulators are ideal for the middle of a dipole where low
weight is important & due to the low the Z the insulation requirements are
minimal. Ceramic ones are best used at the ends were their weight is less
important & will not reduce the aerial's height by as much.
With tough wire a tight wrap of the tail end may be adequate, but for the rope
or thin wire then self tightening knots that do not knot the tensioned feed
line should be used. This is an ugly but safe knot system....
_
free end ___ ___ ___ /~ ~\
==/.-.\=/.-.\=/.-.\==' eye-³
==============³³³===³³³===³³³===. let ³
Load cord \³³³/ \³³³/ \³³³/ \_ _/
self tightening granny "
knots in free cord
TENSIONING
To maintain & control tension on a permanent installation, I use a 10kg heavy
weight (old transformer). But I found this was not too effective, because the
mass & the pulley friction would be slow at keeping the tension, resulting in
the middle of the aerial bobbing up & down with the wind. So I tried adding
some long coil springs out of a chest exerciser (was not mine) or cow fence
types used in line with the aerial give quicker strain relief (no mass) than
the tensioning weight, & maintain aerial tension better. I painted these to
reduce further rusting & one mounted each end just before the insulators. This
has stopped the bobbing around as about 0.5m stretch is available with no slow
mass to allow for the wind & tree sway. A bunjee may have similar performance,
but a short lifetime!
See my TECH bul on "Casting Lead Throwing Weights"
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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