| |
G8MNY > TECHNI 12.01.20 12:03l 263 Lines 12021 Bytes #999 (0) @ WW
BID : 40259_GB7CIP
Read: GUEST
Subj: Tree Antenna Sky Hooks
Path: IZ3LSV<F1OYP<SR1BSZ<SP7YDD<SR8BBS<OK0NBR<OK2PEN<CX2SA<GB7CIP
Sent: 200112/1102Z @:GB7CIP.#32.GBR.EURO #:40259 [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 the line" & then you can loose some line & the weight.
The knot must be a suitable type for mono filament that does not over stress
(knot) the load carrying side, I found several (at least 3) simple loop knots
work on the fee end around the incoming line (see insulator & eyelet diagram
below), & can be undone with patience.
The pre-laying out of 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 a very cluttered site, with great success
getting over specific tree tops/branches at 40m up & clear 30m depth of forest
at the same time. With the fine line needed for log shots, windage is a
problem, & must be considered when aiming so the line drifts into the tree as
needed.
Often a high shot is best coming down in the tree if you can't reach the other
side of the tree!
FISHING ROD
Similar to both of these methods is casting a weight over a tree. Again a far
degree of skill is needed to get the line & weight over the part of the tree
needed as there is no aiming system with a fishing line. But the range
(possibly not height unless you stand on steps for more room) may be well over
other methods!
TWIRLING (Slingless shot)
This method uses stronger line & heavier weight & for temporary aerials
attached to the same line is actually the quickest system.
A weight > 100gm, e.g. plumb bob is tied to nylon cord (e.g. builders orange
marking line) & make sure the fixing is very good & will not pull out of the
weight, & then with a meter of line to the weight you twirl this around in a
vertical manner in line with the target. 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.
|| / \ pay out line
all laid out
Unlike the previous 3 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 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 boat 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 (e.g. 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 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
Read previous mail | Read next mail
| |
