Gareth,
I think the antenna you are reffering to is also called the half Bobtail
curtain version. If i am right you have two 1/4 wave verticals spaced 1/2
wavelength and connected at the top with a horisontal wire ??
I have a bobtail curtain for 40 meters and the spacing i abt. 0.8 of a 1/2
wavelength because of some existing supports. This cause the horisontal wire to
"drooping" a bit. I do not find any degradation with respect to F/S attenuation
it is still 10 - 15 db and I suspect the gain is the same as my earlier " ideal
" setup.
Henrik
Oz1ing
-----Oprindelig meddelelse-----
Fra: Gareth Crispell <gareth@capecod.net>
Til: towertalk@contesting.com <towertalk@contesting.com>
Dato: 14. marts 1998 01:52
Emne: Re: [TowerTalk] Half-square antenna question
>stu wrote:
>>
>> I was looking at some drawings of half square antennas and while most
>> articles said the bottom legs could be bent around without losing much
>> gain I am wondering how much effect moderate drooping or bending between
>> supports of the top horizontal part it would take to degrade
>> performance? I don't have any 3 supports near a straight line so it
>> would be fairly dog legged.
>> 73' Steve KG8TX
>>
>> --
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>
>You only need two supports for the half square. The "bottom legs" are
>vertical radiators and should be as close to straight up and down as
>possible. Think of this antenna as 2 quarter wave verticals phased by an
>electrical half wave. I would put as little sag as possible in the 1/2
>wave horizontal. You can anchor the bottom of the verticals with fishing
>line tied to a cinder block so they don't wip around in the wind. The
>bottoms only need to be about 6 to 8 feet off the ground. Tune to
>resonance with this ratio. For every inch you cut from the feed side
>vertical - cut 3 inches from the far end. Bring the feed line away at a
>sharp angle so the horizontal part does not electrically "see" the
>feedline. Darn good antenna and cheap to build. Low lift angles.
>
>de N1MSV
>--
>
>
>
>.....at the dawn of the New Age of Man,
> they will abide with us.
> Their glory and fire will burn like
> sparks among the stubble!
>
> Gareth
>
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>
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