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[TowerTalk] Ravine span--It can be Done!

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Subject: [TowerTalk] Ravine span--It can be Done!
From: (Jim Reid)
Date: Sat, 14 Jun 1997 15:50:42 -1000

Status of our ambitious project to duplicate a
globe spanning V-beam array a la Lloyd Colvin's
set up in Germany. He described it in QST for August
1956:  four 584 foot wires, spaced every 45 degrees,
covering an arc of 135 degrees.  With switching,
all azimuths are covered,  as the V radiates
approximately equally in a bi-directional pattern,
down about 2 dB or so in the direction of the
V apex from the V "mouth" direction. On 40 meters,
"LB" Cebik has modeled this array:  he finds about
9.5 dBi gain,  at an elevation angle of 17 degrees,
if the set up is about 50 feet high over flat ground.
Of course,  this one is to be over a "jungle" filled
ravine,  but will still be interesting to see how
it plays.

This morning,  with much grunting,  climbing, and *#$@%&,
we got around 590 feet of rope to span the distance.
Required was clearing the top of a 70 or 80 foot
mango tree, getting through a hau tree forest/thicket,
crossing a swamp,  up the other ravine side,  and then
trying,  unsuccessfully to climb many, many feet up into
very high trees! The bow at last solved that problem also.
Fired back out of the forest,  so the arrow fell back
into the swamp!

The entire job,  in fact, could only be done with the help 
of the compound bow and arrow, the game tracker string gadget,  
and several arrow shots!!

The biggest challenge was the hau thicket.  Long ago
the Hawaiians planted hau tree thickets all around
villages as high protection walls.  They are impossible
to cross without a lot of climbing,  limb breaking and
cutting with machete, etc.  We also found that the highest hau
tree limbs know exactly how to reach up,  grab the game
tracker string as it settles down,  and completely
entangle it!!  So we had to climb to the top of the
thicket,  with much added commenting along the way,
to disentangle and attempt to clear the string.

We found it best to pull the Dacron rope along a
ways at a time so as to not put too much pull tension
on the game tracker string at a time.  Eventually,
the Dacron rope will pull the V-beam wires into place,
spanning the ravine and all the wild growth far below.

Of course,  it also required several waddings across the
shallow swamp at the bottom of the ravine, as the game
tracking string continued to get tangled in something
every few moments!!

During such a project,  the shack on the belt becomes a
very handy tool:  "please bring me the machete", "please climb 
around there, and do thus or so",  etc.

Trade winds and rain showers absent,  added legs of rope will
go up tomorrow morning.  Progress will be reported when
the wires are up.  Planning to use 300 ohm windowed twin
lead for the radiating elements.  Choosing this for strength
against the gusty trades and occasional tropical storm winds
that will blow across Kauai.  Will use doubled Dacron 
as the suspending support rope.

These things should work all the way down through even 160,
I hope!  At least a little down there, maybe, as the legs
will be just a bit over one wave long on 160.

73,  Jim,  KH7M
On the Garden Island of Kauai

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