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G8MNY > TECH 30.12.05 12:31l 117 Lines 5342 Bytes #999 (0) @ WW
BID : 11025_GB7CIP
Read: DL1LCA GUEST OE7FMI
Subj: A Light 17m /P mast design. 3/3
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0BEL<GB7CIP
Sent: 051230/1115Z @:GB7CIP.#32.GBR.EU #:11025 [Caterham] $:11025_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
ROTATOR
I use a 12V rotator with a padded out shaft that the mast sit on & a bolt hole.
It is only low torque & easily stalled rotator, so if anything fouls up it
does no damage & keeps it's direction meter in sync! It was made from scrap
army kit.
Captured _ Padded
Nut Hole>³.³ 2" shaft
Water_\ __³_³__
Trap / ³ ³ Geared
³ ³ Down DC
³_______³ Motor & Pot
Base sits on foam sheet
I also use a mains one with over sized clamps that go outside the pole &
rotator, again clamp is done just enough to allow normal levels of torque only.
2.5" ³ ³
Mast ³ ³_
³ ³³
_³_ /_³_
Large==³()³=³³=)³
Clamp ÀÂÄÙ ³ÀÄÂÙ
³ / ³ Mains
ÚÄÁÄÁÄÄÄÄÁÄ¿ Rotator
_³ ³_
Wooden <______________>
Base ____³__________³____
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
Corners Pegged down if needed.
SETTING UP (updated Apr 05)
A wooden A frame supports the mast while the guys, ropes & release cords are
sorted & laid out before the mast is erected.
1 2 3 \ 4 /
Rope tie off ÚÄÄ¿ __ÚÄ_ÚÄ____ `ÚÄ¿'
____ ¿Ú ______......ÄÄÄÄÄij """""\_³(_³(___() ³(³
/ / \____......ÄÄÄÄ-""""""______......ÄÄÄÄÄij_""""""XÀÄÙÀÄÙ ,ÀÄÙ.
³ ³ (_____......ÄÄÄÄÄ"""""" / \ / \
\__\_/ /' A `\
Rotator / frame \
Steel stakes or pegs (8 off painted anything but GREEN) are slightly larger
than large tent pegs are used (eg 30cm x 2cm x 2cm) with sharpened points. Use
with the open V side towards the mast & hammed right in @ 45ø angle, to tie off
the guys in 2 concentric squares.
\ P L A N /
Open part of V
faces mast ./\ \ / Inner
`. ./ __\ Brightly coloured Stake Pegs
Tie Guys`. ./,/' /' Steel Steak Peg 0
at ground `./,/ /' MAST
level /. /' Use Clove Hitch / \
Knots ! Outer
/ \ Stakes
ERECTING
Always start with no aerial or coax load, but allow enough mast space for it &
the coax loop before clamping up the top guy clip.
If the centre location is not to important you can erect the mast singlehanded.
Put 2 pegs in @ 90ø for the lower guys & tie them off (I always use the safe &
quick clove hitch for ties) swing the mast vertical & lean it almost vertical
into the 2 guys. Then put out & loosely tie off the next lower 2 guys. Put the
mast vertical & adjust ties & pegs for a proper square. If not single handed
get 1-4 slaves with different names to put in the 4 pegs.
Then pull the 2nd pole out until it's catch locks. Then put out the 4 guys for
that level to the same pegs. Repeat for guy levels 3 & 4 with a bigger peg
square.
When all is well & vertical, lower the mast leaving all guys in place. This
MUST BE DONE IN REVERSE ORDER so that the mast is supported as comes down.
Pull on the heighest pull up ropes to take the load of each catches before
attempting to release the heighest catch. When all telescoping is done just
lift & move the base away keeping the top about were it was. Put mast back on A
frame. Run out all the spare guy strings towards their respective pegs to keep
the tangle around the mast at minium. Attach aerial & coax , with the weight if
it it carried on the top giuy plate.
Re-erect the mast, you may find minor guy adjustment is needed to keep the mast
vertical (straight is more important) now it is under load.
IN USE
Because this is a light weight mast, erection & de-erection is ONLY POSSABLE IN
NO TO LIGHT WINDS, wait for lulls (evening or morning). However once up, the
mast has survived strong winds (>50MPH) if the relevant guys are adjusted to
keep the mast straight. Vertical is not so important!
In public demos etc. I do not let the public in the guying area, which is
bigger than the drop zone. But one advantage of it is that it can be put in
between marquees etc. where other masts would need a huge erection area. If
tying guys to ladder racks on cars vans etc. make sure owners do not drive
away!!!
If the mast should collapse in a storm etc, in my experience it will fold &
kink one of the middle tubes lowering the aerials VERY slowly (work hardening
absorbing most of the energy) without the aerials or anything of the ground
being damaged.
Aerial used on it (one at a time) are:-
Length Weight Type
6.6M (22ft) 5.0kg 17el 2M by Tonna, (but often stripped down to 11 element)
3.0M (7ft) 2.0kg 8el 2M Quad Homemade 2 thin boom type,
6.2M (20ft) 4.0kg 27el 70cm QLY by G3JVL,
4.0M (13ft) 4.7kg 88el 70cms Multibeam by JBeam,
2.1M (7ft) 1.5kg 24el 70cms beam,
5.0M (18ft) 2.0kg 55el 23cms by Tonna.
And with some of the above plus a /M Colinear whip & a halyard for HF wires.
Coax used is the lightweight low loss POPE H100.
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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