Posted by
Michael Babineau-2 on
Jun 20, 2010; 2:58am
URL: http://elecraft.85.s1.nabble.com/Antenna-for-a-KX1-tp5196274p5200126.html
Arnie :
I have found that a 28 ft "sorta-vertical" wire to be a bit less picky w.r.t. positioning than the 24 foot wire.
It will match equally well on 20m and 30m but is somewhat easier to match on 40m than a 24 footer.
The 24 foot wire will match fine with the KXAT1 on all three bands as long is it is quite vertical.
BTW what you want is the POMONA BNC to binding post / banana adaptor.
Note that the POMONA adaptor allows two banana plugs to be connected to each terminal.
The RED terminal goes to the center conductor on the BNC and the Black the BNC shield
on the rig.
I also highly recommend the Radio Shack solderless Banana plugs. The wire is
secured by a screw-on metal shell ... and my recommendation is that once you
install it put a dab of LOCTITE or clear nail polish or it will eventually come
unscrewed and you will lose the shell part in the grass ! It put these on the ends of
all of my portable wire antennas.
For a ground plane I use a 20 foot length of 5 conductor computer ribbon cable
with all 5 wires connected to a R/S solderless banana plug. About 4 feet from
the plug I put a piece of electrical tape then I go to the opposite end of the
ribbon cable and unzip all of the wires up to the point of the tape. This
provides a clean way routing the ground plane wires away from the rig
and then the wires splay out on the ground. I find that this
is pretty quick to deploy and works pretty well from most locations that I
operate. If I feel I need more radials I have a second set of 5, identical to the first
so I can deploy 10 which is about the limit of my patience in deploying radials.
;-)
I did a lot of experimentation trying to come up with a shortened wire antenna that could be supported by a 20 ft
Crappie pole such as the Black Widow or Shakespeare Wonderpole that would work on 40m through 20m
with the internal tuner in the KX1 . What I finally settled on and have been using for portable operation with my
KX1 for some time is a 20 ft linear-loaded wire made from R/S indoor twinlead.
Details as follows :
Vertical radiator is a 20 foot piece of twinlead with the top shorted (ie both
wires connected together at the top end and soldered). I just tape the twinlead
to the fiberglass pole.
The two bottom wires on the twin lead each have their own R/S solderless
banana plug installed.
On 20m and 30m both bottom wires on the twinlead are connected to the center
conductor of BNC on the rig via the RED terminal on the POMONA adaptor,
making the antenna just a fat 20 foot wire.
On 40m only one of the two bottom wires on the twin-lead is connected to the
center conductor of the BNC on the rig via the RED terminal on the POMONA adaptor
(the other wire is left floating) this effectively creates a 40 foot vertical wire folded back on itself
at the 20 foot mark.
On 40m the folded wire creates a linear loading effect due to the capacitive
coupling between the two wires (note that currents are not equal and opposite so
there is no cancellation of signal as you might initially think). This added capacitance
allows the wire to be resonated on 40m by the internal tuner in the K1, KX1 or also
by the Elecraft T1.
In both cases my ground radial system is connected to the BNC shield via the
BLACK terminal on the POMONA adapter.
Note that 20 feet is not that far off of the normal 33 feet required for a 1/4 wave
so the performance is not bad on 40m.
This is a very simple antenna that works well on 40m through 20m.
I have made hundreds of QSOs on 40m/30m and 20m operating portable with
this setup.
Best of luck with your "new" KX1.
Michael VE3WMB
P.S. I also discovered that a 14 foot piece of twinlead in the "linear-loaded configuration"
will load fine on 40m when supported on a 13 Ft fiberglass pole and I use this with a 29 foot
trailing wire for pedestrian mobile operation with my KX1.
Note that when the twinlead wires are shorted at the bottom to make a "fat" 14 foot wire this
will load fine on both 30m and 20m. Actually the minimum length of wire that will match
on these two bands is about 12 feet.
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