Hi.
I was trying to build a field portable quick to
install
antenna and I really liked what I read about an end
fed
halfwave having a very low angle of radiation and only
requiring a very short counterpoise however
I remembered that the KXAT1 manual stated not to use
lengths near a halfwave as they would be outside the
matching range.
So... I decided that I would cut an antenna to 33ft
(20m halfwave), and then I would cut it back a foot at
a time until the KXAT1 found a match.
I started at 33.25ft vertical but I did leave a pair
of
18.5ft counterpoise wires running at about 2 feet
above the ground connected to the ground terminal.
I tuned up and ... 1.2:1 match on 20m!
I then proceeded to work KF6GC with 2W (almost 4000km)
in the middle of a K Index = 8 solar storm! So I know
the antenna worked well.
I modelled it in EZNEC and the impedance at the base
of that antenna should have been 970 + j 1700 ohms,
so I am surprised that the KXAT1 was able to match it.
Any comments? Was it because I left the counterpoises
connected that it worked so well? If I remove the
counterpoises in the NEC model the impedance increases
and becomes inductive to 1456 - j 1819 ohms.
Comments?
PS. I am only learning in this stuff so forgive any
overly simplistic analysis!!
Thanks,
Martin.
VA3SIE.
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