N4KG response below.
On Thu, 26 Apr 2001 "Bill Hider" <n3rr@erols.com> writes:
> 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.
>
So, would you be willing to throw away 4-6 dB gain on the highbands?
Given your same conclusion, you could replace all your Yagi's
with simple DIPOLES.
Yes, a dipole is a GOOD antenna, but some people go to LOTS
of expense and effort, i.e. stacks, to pick up 2 to 3 dB gain.
FWIW, I've worked over 320 countries on 80, 40, 30, 17, and 12M
using only Dipole antennas, plus a single vertical on 80.
Bottom Line: For SERIOUS DXing, it may be useful to have a
PAIR of 80M inverted vees at right angles to each other, even
at 70ft. My experience with 80M inverted vee's is that they really
start to 'play' at 90 ft and higher.
de Tom N4KG
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