On Tuesday 20 July 2010 19:54, Lew Sayre wrote:
> I'm pondering putting up a 4 square. An early problem would be the effect
> of having the bases of each element at a different elevation relative to
> each other. The QTH is on the top of a ridge so the bottom of each element
> could be as much as 10-20 feet different in elevation. Would this
> seriously screw up the efficiency of a 4 square? a little? a lot? I know
> that the radiation into the hill will be hurt but what about the other
> directions? Ridge runs about 330-150 deg.
> Just trying to reason this through a bit before putting serious wire
> in/on the ground.
> Tnx for any facts, observations, educated estimates or just wild-ass
> guesses.
> 73 and I remain,
> Lew W7EW/W7AT
Lew
DX Engineering says two things:
"The system is forgiving, but the best front-to-back is obtained when symmetry
is maintained and with each element resonant on the same frequency and with
each antenna base at the same elevation." and
"It's recommended the maximum ground height difference between any of the
vertical antennas in teh array should be less than 20% of the array diameter.
For example, a 64 foot square array should be within 12 feet of level."
Eleven years ago when I was planning an 80m 4-sq, I asked the antenna
reflector if keeping the antennas in the same horizontal plane was important,
and most of the guys said it was. So I designed it around rohn 20 or 25
tower sections that were as short as 7 feet above ground up to 17 feet above
ground, and I used elevated radials. A friend with a transit was a great
help, but a laser leveler will help. And you will get many chances to
exercise your math skills.
I have had much success with the array, and it does a lot to the ego to beat
out one or the other coast from Iowa.
tom WB8ZRL
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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