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VK3ABK > WANTED 21.09.04 04:50l 31 Lines 1260 Bytes #999 (0) @ WW
BID : 24093_VK3KAY
Read: GUEST
Subj: Re: 70MHz Horizontal Mobile Ant?
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0RES<ON0AR<ZL2BAU<VK3KAY
Sent: 040921/0333Z @:VK3KAY.#WEV.VIC.AUS.OC #:24093 [Wendouree] $:24093_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : WANTED@WW
Hello ZS1DJ etc..
The bulletin from Eldred, asking for help with a mobile HF antenna, and a
reply from Rudolf, PA2RHB, made me think of an alternative which was
suggested many years ago. 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.
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. It is fed and tuned in a
similar way to the Halo; a 'grounded' mounting at one end, and a tuning
capacitor at the other, with a feed point for coax at a suitable point
from the grounded end. Note! it is only a 'quarter wave' length of tube
or heavy wire, bent into a circle, using insulators for support from the
ground plane or car roof, A 'Halo' is a 'half wave' length.
Mounted about 0.1 wavelength above the groundplane, with several insulators
for support, the DDRR antenna could be more acceptable on the family car.
More details in 73 magazine June 1970, and QST December 1971.
Hope this is of interest.
73. Dick. VK3ABK.
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