| |
G8MNY > TECH 03.07.07 18:52l 217 Lines 9977 Bytes #999 (0) @ WW
BID : 21145_GB7CIP
Read: GUEST OE7FMI
Subj: Tree antenna sky hooks
Path: DB0FHN<DB0NOE<DB0GAP<DB0SAA<DB0GPP<DB0OFI<DB0PRT<DB0LHR<DB0GE<LX0PAC<
DB0NDK<DB0MKA<DB0ACC<DB0GOS<ON0AR<GB7CIP
Sent: 070703/0728Z @:GB7CIP.#32.GBR.EU #:21145 [Caterham] $:21145_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated May 07)
(8 Bit ASCII Graphics use code page 437 or 850)
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) are small & not very visible so use brightly coloured
ones eg. Orange/Red not green/yellow/brown, as this will help spotters the
other side of the tree to see the shot. The pre-laying out of the unknotted
line is very important, but I have seen combined fishing reels used (on handle)
with only occasional line fouling.
_
Tube /~/~\
ÉÍ==============(<°°°°³ Flatted Sling stretched >
Y Steel º Rubber Shot\_\_/ leather/Rubber to here to fire! >
º ~ sling
º³
³~³
³ ³
³_³Handle
I have seen this method used for very cluttered site with great success getting
over specific tree tops/branches at 50m up & clear 100m depth of forest at the
same time. With fine line windage is a problem & must be considered when
aiming so the line drifts into the tree as needed. The tree foliage causes the
same problems as the arrow method.
TWIRLING (Slingless shot)
This method uses stronger line & heavier weight. A weight > 100gm eg. plumb bob
is tied to nylon cord (make sure the fixing is very good & will not pull out!)
and you twirl this around with a meter or so of line. Your hand needs
protection & a leather glove must be worn. As there is danger of 'miss fire' is
you let go at the wrong time, make sure other people & cars etc. are well
clear!
M E D I U M twirl dia
S I Z E D . Ú .
T R E E . o.
|| v ()/'. `ú.
|| . ų .^ `ú.
|| / \ Line laid out
Unlike the previous 2 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 18M with this method. Due to the
heavier weight, tree grabing of the line is less of a problem, 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!
TALL POLE METHOD
This is a non ballistic method. I use 17m of very thin set of telescoping
poles. eg. 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 thiner pole & the clamp
over the larger one.
³ ³ U clamp
³_______³_/
(__________]NUTS
³ 5øAngle ³Pole
³ pole cut³higher
³ ³
The top pole 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 over a
suitable branch, lower the weight. With careful jiggerling the weight should
come down ok through the tree branches. Avoide 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 greased. (eg. hot runny grease dripped in to centre axle).
Cast _ Type Simple Open type Modified
(0) |~| 0 0 0 0
ÉÍÏÍÏÍ» .ÁÄÁ. ÚÄÄÐÄÄ¿ Úп ÖÄÄÐÄÄ· _.Úп.Key
º Ropeº / \ ³ Rope³ ³ ³ º Ropeº / |³ ³| \
º³\_/³º | | ³³\_/³³ /'³ ³`\ º³\_/³º | ³ ³ |
º³ | ³º | | ³³ | ³³ | ³ ³ | º³ | ³º | ³ ³ |
̵ | ƹ | * | Ƶ | Ƶ | ³o³ | ̵ | ƹ | ³o³ |
º³ | ³º | | ³ | ³ | ~ | ³³ | ³³ | º |
º³/~\³º \ / ³/~\³ \ ___ / ³³/~\³³ \_ º _/
ÈÍÑÍÑͼ `ÄÂÄÂÄ' ³ ³ `-_º_-'
(o) |_| slotted plates
~
On simple open ones where there is a real chance of the rope fouling when it
come off the pulley, I found that a piece of suitably cut tin plate could be
added to each side of the pulley block wheel to stop the rope fouling & jamming
the pulley by falling off the side of the wheel. The slotted plates have a key
cut at the top to locate the inverted U bracket, they also have bent back edges
to be smooth to the rope.
Much better & more expensive types are available from chandlers.
The halyards are threaded up to be continuous loops so that if the aerial
breaks then it can still be lowered. Also for the tree end there is a put up
rope that was placed over a high branch to hall the halyard pulley up.
Polypropylene rope (eg. 6mm draw rope) is OK, but does have a short lifetime of
only a few years in the sun before it disintegrates! Never trust it for
dangerous work where people could get hurt!
Tree.....Pulley Spring
: O.......eee.ì----
: : / Insulator
: : / Loose
: : / Pull Down
: : / Loop
: : /
: Tension
Tie Off Weight
Note 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 excellent insulators at ham QRP levels (<1KW). But in permanent &
for wet conditions good insulators are needed as arcing/losses could occur.
.===-.. ... =:\
/ _ `\\. /'_ """\\\
==////=======) 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.
With tough wire a tight wrap of the tail end may be adequate, but for the rope
or thin wire then self tighting knots that do not knot the tentioned 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). 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!
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
