On Wed, Jan 29, 2014 at 07:54 AM, Tom W8JI wrote:
> How much I can improve by moving the coil up. What improvement should
I expect if center loading at about 7 meter? How about moving the coil
all the way up to the top loading spokes? Is it worth the effort? (the
pole won’t support much up there).>>>>
The coil does not do much at all to current distribution. The spokes
pretty much set the current distribution in the antenna, so moving the
coil would have almost no effect.
73 Tom
Here we go again, Tom spreading misinformation.
IT IS important where the coil is placed in the loaded antenna.
See the discussion at http://www.k3bu.us/loadingcoils.htm
Also, QEX finally started publishing Barry's, W9UCW articles in QEX
Jan/Feb 2014 issue describing actual measurements and results of their
experiments.
Interesting, that Tom admits that there is cos (diminishing)
distribution of current along the straight wire - radiator, but when you
roll that wire into a coil - magic - current becomes constant across the
coiled wire according to Tom.
The suggestion about loading coil placement to improve efficiency of
(resonant 1/4 wave) antenna (trying to maintain maximum length of
radiator with highest current) is to place the coil furthest away from
the feed point. The further we go, impedance along the wire increases
and number of required turns increase in order to maintain resonance for
the length of wire, while having high current portion of the radiator
the longest - stronger radiated field.
My most effective mobile 160m antenna was fender mounted Hustler mast
with loading coil on the top and loading wire going to the short mast on
the front bumper of 1972 Buick LeSabre.
Yuri, K3BU.us
www.MVmanor.com
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