Posted by
Don Wilhelm-3 on
Sep 10, 2005; 2:41am
URL: http://elecraft.85.s1.nabble.com/KX1-Antenna-Idea-tp382007p382014.html
Dan,
Actually, in my experience, the tuner could care less whether the load is
balanced or unbalanced, it will just do its best job of matching the
impedance it sees regardless of balance.
OTOH, if you are concerned about radiation patterns, or 'RF-in-the-shack',
it would be prudent to install a balun. For most situations (multiband
use), I recommend a 1:1 balun over a 4:1 because it and the tuner will
handle a greater variety of loads compared to the 4:1. The only important
parameter that you need in a blaun is the ability to reduce or eliminate RF
on the outer side of the coax shield (common mode current), and a simple
choke made by coiling up a length of coax will do the job fine, as will the
type with a ferrite beads on the coax (W2DU type). One thing that is
certain, use a current type balun, the voltage type balun will not handle
reactive feedpoint impedances very well, where the current type
(particularly the 1:1 balun) will handle it much better (note that
everything is a compromise when multiband antennas are addressed).
73,
Don W3FPR
> -----Original Message-----
> Hi again--
>
> Last night, I worked a guy who also is a KX1 owner, and we
> got to talking about antennas. I mentioned that while the
> antenna suggested in the antenna tuner manual (24-28-ft.
> driven element with a 16-ft. counterpoise) tunes up OK, I
> was kind of disappointed in the performance. The other guy
> mentioned that he uses a 40-meter doublet, usually in an
> inverted vee configuration, fed with ladder line, and that
> it tunes up well on all three bands.
>
> I asked him whether or not he used a balun, and he said no,
> he just fed it directly into the radio. I suppose his
> antenna could be fairly well-balanced or that the KX1 is
> able to tolerate a fair amount of imbalance.
>
> Whatever the case, I was thinking that it shouldn't be too
> difficult to build a small balun--and it really could be a
> small one since the maximum power level it needs to handle
> is just 5W--into a small plastic project box. On one end,
> the box would have two binding posts to connect the ladder
> line, and a panel-mount male BNC (if they make such a thing)
> on the other.
>
> Does this seem reasonable to do or is it overkill?
>
> 73!
>
> Dan KB6NU
>
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