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K0CQ > HELP 10.04.07 16:03l 33 Lines 1240 Bytes #999 (0) @ WW
BID : 34457_W0AK
Read: GUEST
Subj: Re 1/2 wave End-Fed
Path: DB0FHN<DB0MRW<DK0WUE<7M3TJZ<IK6PYS<ON0BEL<N4ZKF<KQ0I<W0AK
Sent: 070408/2212Z @:W0AK.#CIA.IA.USA.NOAM #:34457 [Des Moines] $:34457_W0AK
From: K0CQ@W0AK.#CIA.IA.USA.NOAM
To : HELP@WW
A three quarter wave wire has a low impedance but no radiation at
right angles. Wadding up that end quarter wave (in a coil or a
matching stub) to not radiate makes a working half wave and
doesn't change the match drastically. The same thing is true of a
5/8 wave with 1/8th wave of wire wadded up or coiled or put into
a stub to minimize its radiation.
Otherwise an end fed halfwave can be feed with a quarter wave
stub, or a parallel resonant link coupled or tapped tuned
circuit. Anything to match 1000 ohms to the feed line, though the
feed line can be part or all of that match.
> I mentioned a simple series coil being used with a 5/8 antenna to make it
> up to 3/4 wavelength, to provide a low-Z feed. I can think of no reason
> for this not also being applicable for a 1/2 wave antenna.
> The series coil actually performs two functions:
> a) impedance matching and,
> b) being coiled up, its radiation is minimized.
> The latter point is important because the current in that section is out
> of phase with the current in the halfwave (radiating) section of the
> antenna.
> Cheers ... Ray
I agree completely.
73, Jerry, K0CQ @ W0AK.#CIA.IA.USA
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