Hello Topbanders
I'm new to the reflector so I'll introduce myself. I'm Jim Kingsbury NW6S
and I retired (mechanical engineer) from CA in Nov. 96 and moved to western
NC. It's nice to have almost and acre instead of a 60 by 110 foot lot!!
I'm not new to ham radio, but fairly new to 160 and vertical antennas.
I want to put up a dual band vertical for 80 and 160 meters using
nonresonant (<> 1/4 wavelength) elevated radials. My reasoning for this is
that my lot doesn't allow for full 1/4 wavelength 160 radials in all
directions and I believe from what I've read that nonresonsnt radials are
more forgiving on current distribution when not perfectly tuned. I plan to
use radials that are 120 degrees on 80 (about 94 feet) which will be 62
degrees on 160. I plan to use capacative tuning on 80 and inductive tuning
on 160.
I am thinking of making the vertical element out of 110 +/- feet out of 450
ohm ladder line going up into a tall pine tree. I will cut one leg of the
line at about 70 feet to act as a quarter wave length on 80 meters. Then I
plan to connect the two legs together at the top to form the 160 meter
element. It will go up 110 feet then back down 35+/- feet at a spacing of
about 1 inch. My first question is will this act as linear loading on the
element and if so how do I calculate the effect of the loading to determine
what length to cut the element?? My second question is this even feasable
or just fuzzy thinking on my part? Would I be better off to just put up 70
feet of ladder line and extend one leg to 135 +/- feet in an inverted L
configuration??
I looked in several references for an equation to calculate the reactence of
a non-quarter wavelenght radial and could not find an equation for this
calculation. I finally came to the conclusion that I needed to use the
surge impedance equation for a beverage antenna (z=138Log(4h/d) to calculate
the characteristic impedance of the radial and then use the reactance
equation X=Z/tanl (where l is the length of the radial in degrees) to
calculate the reactance. This gave reasonable results, but again I'm not
sure if it is correct or more fuzzy thinking. Would appreciate you
comments.
The next question I have is do radials act as parallel circuit elements or
something else? If the reactance of a radial is 250 ohms, is the reactance
of 10 of these radials 250/10=25 ohms or do they combine in some other way??
My last queation is if I use elevated radials (10 feet high) should I also
earth ground the the coax shield as well or let the radial system float??
One other question. Is there any concensus on wether the ewe, flag or K9AY
loop are better small area receiving antennas?? I know that beverages are
considered the best but what is second choice??
Thanks for reading and responding to my questions. I would appreciate not
only answers to my questions, but any comments you might have. I'm trying
to learn. I've read your e-mails on the reflector and heard many of you on
the air and maybe worked some of you in the contest a few days back. I'm
looking forward to some sleepless nights and early mornings.
Please respond to NW6S@ARRL.net or here.
73 and Thanks again Jim NW6S
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