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KB2VXA > AERIAL 10.01.10 22:18l 40 Lines 1792 Bytes #999 (0) @ WW
BID : 49365_VK6ZRT
Read: GUEST
Subj: Re: VE3WBZ > Interesting results
Path: IZ3LSV<IK2XDE<PY1AYH<OK4PEN<OK2PEN<VK6HGR<VK6ZRT
Sent: 100110/2017Z @:VK6ZRT.#BUN.#WA.AUS.OC #:49365 [Boyanup] $:49365_VK6ZRT
From: KB2VXA@VK6ZRT.#BUN.#WA.AUS.OC
To : AERIAL@WW
Hi Pete and all,
No need to check the book, there is a simple explanation why in this
application a screen is preferable to radials. It's all in the earth
counterpoise, radials take the place of the Earth so even when on the
ground or slightly buried they should be at least 1/4 wave at the lowest
operating frequency. Look at a vertical as a dipole turned 90 degrees
with 1/2 underground completing a 1/2 wave antenna. A 1/4 wave vertical
is incomplete without its other half, that phantom half of the dipole.
Either radials or the Earth itself completes the circuit and since
radials need extrordinary length in portable operation the Earth itself
substitutes as it does in mobile operation. The vehicle provides
capacitive coupling to earth and in portable a screen substitutes for the
vehicle. While radials may be more easily stored and transported when
they get long it's another story so a screen folded and stacked makes a
viable alternative.
As an aside, one may compare this arrangement to a mobile VHF antenna. In
this case the vehicle itself is the earth counterpoise since when
properly mounted there is at least 1/4 wave planing surface surrounding
the antenna. Now take the mag mount, where's the ground? Right where we
left it under the antenna but now we're using capacitive coupling to the
ground plane.
I hope this clears up some common misconceptions that have crept in
thanks to some people too lazy to read the book and others too lazy to
get a second opinion. NOW hamsters get off your butts and call my bluff,
read the book! (;->)
Sarcasm mode... off.
73 de Warren
Station powered by JCP&L atomic energy, operator powered by natural gas.
Message timed by NIST: 20:17 on 2010-Jan-10 GMT
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