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[TowerTalk] V-beam Gain and R+/-jX

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Subject: [TowerTalk] V-beam Gain and R+/-jX
From: (Jim Reid)
Date: Fri, 18 Jul 1997 08:47:04 -1000
At 09:32 AM 7/18/97 +0400, you wrote:
>Hi Jim,

>Thanks for all the informations that you passed along on the reflector.
>Could you indicate at what heigth was Lloyd Colvin using this V-beam?
>       73! Herik.

Aloha Herik,

Unfortunately,  Lloyd does not mention the height of his V's in his
QST article. Lloyd's only comment about height is that both ends
of each leg, apex and far end, "should be close to the same
distances above ground" and from nearby objects.  Height is,
perhaps not too important,  as V's have pretty low radiation
take-off angles; AO shows some band freq's with max gain
occurring at 6 degree launch angles,(of course,  
in free space).  Many today suggest sloping the far end
of the V's toward the ground,  to lower the max gain take
off angle to the horizon;  but, if you don't terminate the
far end,  and want a bidirectional pattern as Lloyd did, then
more level mounting, and as high as possible is the way to

My primary bands of interest with these will be 80, 40 and 30; the
tribander takes care of the higher bands,  but of course, will fool
around with the V's all the way up to 10 to see what happens. I understand
from those that know such things,  that my 40+ year old Johnson
Big Box will not tune on 160,  and may not on 30;  but I will sure
try to get 30 one way or the other.  May just try a 1:9 balun
transformer and use my Classic Lowbander XMatch tuner with the
V's on 160.

The figures from AO are given for the array mounted
in "free space" with symmetric legs.  This eliminates any added gain or
loss,  etc as a result of ground reflections, ground characteristics,
slopping,  hills near by,  etc., etc.  The idea of AO is just to
get a set "optimized",  then perhaps fine tuned via TA IF you really
know your ground conditions -- I don't,  except that my V's will
span across a ravine heavily vegetated in trees, very tall grass, and
very wet (swampy) at the bottom.  I am about 2 miles inland from
the Pacific directly to my South,  and the V mouths will all face
to the horizon in a total arc of about 135 degrees or so, roughly
to the SE, S, and SW.  The outer legs,  that is wires 1 and 4,
will be fed to form an obtuse angle V,  as Lloyd did, to form a 
bidirectional beam more or less E-W.  None of the V's will be
terminated so all will be approximately bi-directional.  From
my QTH,  I look down toward the Pacific from about 540 foot elevation,
some two miles to the ocean, so the back lobe of the V's will
be the short path direction to Eu, Asia, and the US mainland/Wst-Africa
which are in line from here. However,  many ops here in Hawaii have
often noted that the best paths from here to the mid-East, Asia,
and Europe are all the long paths, and I also can vouch for that,
at least on 20!

Now,  must just wait for better weather to get on with the project.

73 and good DX,

Jim, KH7M

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