Tom,
Think about what you are trying to do from an antenna propagation
point of view.
As stated, you wish to obtain some kind of directivity-switching by being
able to switch
from one set of inverted "V" wires to another set, right?
Well, at 70 feet high, a 75/80M inverted "V" has little or no
directivity.
An 80M inverted "V" at 0.5 wavelengths high (130-140 feet)
exhibits approx a 6 dB front to side ratio. (At 32 Deg elevation take-off
angle.)
REF: ON4UN's Low Band Dxing Third Edition, page 8-19.
At 0.25 wavelengths (approx 70 feet) that would drop by
1 or 2 dB (ibid., fig 8-5, page 8-6), making it essentially omnidirectional
with a front-to-side of
4-6 dB (or approx one S-uint).
So, in my view, there would be no point in building a "steerable" 80M
inverted "V"
with an apex at 70 feet using guy wires or any other mechanism.
That said, I've used inverted "V" antennas for over 30 years on 160, 80, 40,
and 20 M,
including 80M inverted "V"s with an apex of 52 feet. They perform
very well. I've worked much DX with that "low" 80M inverted "V".
I currently use a 160M inverted "V" with an apex at 134 feet, and it
is a barn-burner of an antenna. Note that this antenna is a scaled
version of what you are contemplating - It's at 0.5 wavelengths
high and is quite omnidirectional. Check out the details
at: www.erols.com/n3rr
So, abandon your idea of a steerable switching 80M
inverted "V" at 70 feet as a waste of time and energy for only
4-6 dB of "steerabiltiy", but don't abandon your idea of a fixed 80M
inverted "V"
at 70 feet. It will perform excellently (albeit omnidirectionally).
73,
Bill, N3RR
----- Original Message -----
From: Tom Mattus <wa9wsj@yahoo.com>
To: <towertalk@contesting.com>
Sent: Thursday, April 26, 2001 2:43 AM
Subject: [TowerTalk] Guy wires as inverted Vee?
> Hello again! What is the collective wisdom on using
> guy wires as an inverted Vee? Specificaly for 75
> meters, maybe switchable from side to side? Since I
> have the opportunity to incorporate this idea, before
> the system is constructed, I would like to know if it
> is really that good. What complications might I be up
> against? They will be on a 70' tower. Hmmm, another
> thought, would it be more efficient to load the tower
> instead? Insulating the guys from same, etc...
> I haven't run across this in the archives, unless I
> just missed it, a guy can go stir crazy looking at all
> that good info!!!
>
> Thanks again,
> Tom
>
>
>
>
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