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PA2RHB > WANTED 21.09.04 11:50l 33 Lines 1172 Bytes #999 (0) @ WW
BID : DF0041PA2RHB
Read: GUEST
Subj: Re: 70MHz Horizontal Mobile Ant?
Path: DB0FHN<DB0RGB<DB0MRW<DB0ERF<DB0FBB<DB0GOS<ON0AR<ON0AR<PI8WFL
Sent: 040921/1034Z @:PI8WFL.#NH1.NLD.EU #:47828 [Enkhuizen] $:DF0041PA2RHB
From: PA2RHB@PI8WFL.#NH1.NLD.EU
To : WANTED@WW
X-Info: uploaded with password authentication at PI8WFL.#NH1.NLD.EU
VK3ABK, Dick, wrote:-
> A 'Halo' for 4 Metre is a bit big and may get
> caught up in garage, car-port, or low flying objects! We used them on
> 2 metre AM mobile, but that would be about the limit for convenience.
It was the smallest I could think of. The diameter would be under 70 cms,
much less than the width of the car roof. You could mount it lower (in
terms of wavelength) than you ordinarily would a 2 meter version.
For any horizontal 70 MHz antenna over a ground plane, 30cm seems to be a
practical minimum, otherwise you would get too little lower angle
radiation.
Of course you could build an even smaller one and use an end capacitor to
tune it.
> The DDRR antenna ( short for 'Directional Discontinuity Ring Radiator')
> is mounted close to a conducting ground plane ( maybe a car roof ) and
> is much less in diameter than a corresponding Halo.
Yes, but the trouble with the DDRR is that it is a vertically polarized
radiator. ZS1DJ would like a horizontally polarized antenna on his car.
Ruud, PA2RHB @ PI8WFL
Heemskerk, JO22im
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