Posted by
Ron D'Eau Claire-2 on
Jun 17, 2005; 2:07am
URL: http://elecraft.85.s1.nabble.com/may-have-it-wrong-tp379460p379467.html
Mike asked:
Please correct if this is wrong, I am trying to use my KX1 but after reading
the group emails, I may be doing this all wrong.
For frequency 7118, I took a length of bare copper wire 33 feet long,
divided (that is cut it ) it in half, took one half to the center of the BNC
connector on the side of the radio and the other half directly to the
grounding rod attached to the house. but from reading the emails on the
group list it now appears I need to have a insulated coax and I should not
be connected directly to the radio with the two bare copper wires.....
--------------------------------------------
Your setup is FB Mike. There's absolutely no need to use a piece of coax
unless you must have a transmission line to bring the antenna indoors
through electrically noisy areas that might cause you trouble.
A transmission line has only one job: move the RF between your rig the
radiator (antenna) somewhere out in the clear (hopefully) with a minimum of
pickup or radiation that might cause you problems.
But every transmission line has a lot of considerations to avoid excessive
loss. EVERY transmission line introduces losses - it's just a matter of the
degree of loss. Well designed antennas can show lots of gain produced by
having the radiator out in the clear and hopefully up high that far exceed
the losses in the line, so the line is worth while.
If you're outdoors or if you are sitting by a window in the house,
especially if you're on an upper floor, by all means simply hook two wires
to the KX1: one to the case and one to the center pin of the antenna
connector. Run them out the window. Let the ATU tune up and you're all set.
Ideally run the two wires in OPPOSITE directions as much as you can, or at
least at an angle that has as a minimum a 90 degree angle between the wires.
That's because if they are at too acute an angle they will try to act like
an open wire transmission line and the radiation will be suppressed.
Ideally on 40 you'd have two 33 foot lengths instead of two 16 foot lengths,
but a 33 foot length will be close to a half wave on 20 meters and the ATU
may not be able to match to it. So your choice of two 16 foot lengths is a
FB compromise that should allow the ATU to find a match on all three bands.
Ron AC7AC
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