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Ken Fowler · October 12th 08, 02:51 AM posted to rec.radio.amateur.antenna

On 11-Oct-2008, wrote:

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Subject: Half Size 40M rotatable dipole.
Date: Sat, 11 Oct 2008 01:35:34 -0700 (PDT)
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Hello all. I am looking at building a half size rotatable 40M dipole.
It will be approxiamately 10 metres long end to end. It will have a
loading coil in each leg with about 5 metres of wire wound on a nylon
former. My question is, where would be the best spot to mount the
loading coils? Half way along each leg, ie- about 2.5 metres from the
feed point or should the coils be mounted closer to the feed point? I
realise that this antenna will be inferior to a full size dipole, but
a half size one will fit where I am located.
Any constructive ideas or experience with loading coils would be
appreciated.
Cheers
Max

Where you place them is probably not too important to the performance but
the inductance needed increases as you move away from the center. The
center impedance will be lower than the nominal 72 ohms. EZNEC is good
for evaluating the size of inductance and effect on center impedance. Reg,
(SK) G4???, used to have programs, where you could plug in lengths and
inductances and get answers about F and Z. I believe someone on this
newsgroup archived his programs.

73. Ken Fowler, KO6NO

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