Craig and all,
You have received a lot of advice, and most of it was probably pretty good
advice. I would want to know a few more things about your situation if I
were to make any recommendations which I thought were very precise. Of the
responses I read, I think the best ones (my opinion) came from Don Wilhelm
and Jim Brown. Don focused on your stated preference for 40 and 20 meters,
and Jim added some good advice about vertical alternatives.
You didn't say exactly what flexibility you have about erecting an
antenna--trees, space, etc. If you want to work DX, you need to try and get
your antenna up in the air as high as possible--at least 40 ft. or more.
That's particularly important if all you are able to do is run at near QRP
levels with a barefoot KX3. Resonant dipoles for 40 and 20, at a decent
height, should allow you to achieve some success, and they are relatively
easy to construct.
You don't mention if you have a tuner, or if you purchased the ATU accessory
for the KX3. If you don't have either, you should probably invest in one.
The KX3's internal ATU is excellent, but even a simple tuner like an MFJ,
can give you several added options. One is a single dipole fed with
balanced feed line, which will probably allow you to operate several other
bands. When using balanced feed line and an internal ATU, a balun like the
Elecraft BL-2 may be a necessary addition. That is switchable between 1:1
and 4:1, and the 1:1 setting will probably be your best option generally.
This can be a very versatile arrangement, and not difficult or expensive to
construct. you can erect it as a horizontal dipole or an inverted vee,
depending on what you have available for supports.
Several responders mentioned commercial alternatives. End Fed Half Waves,
like those from PAR Electronics (now LNR) do work quite well. Some models
are power limited, so choose accordingly. The Par 10/20/40 is a good choice
to match the KX3, but again, you should try and get it up in the air as high
as you can.
Commercial multi-band verticals can be expensive, but I like Jim Brown's
recommendation for something in the Cushcraft R series. I've used an R8
(and also the R7 which preceded it) for years with very good results. As
Jim says, put it up off the ground if at all possible. Mine is about 15
feet above the ground, and works considerably better than when I tried it
ground mounted. Some others mentioned a Gap Titan, which will give you 80
meters as well (the R8 only goes down to 40 meters), but performance on that
band is very marginal! You would probably be much better off with the
dipole/balanced feed line system I mention above so long as you can make the
radiator part at least 100 ft. long or so. An 88 ft. version suggested by
L.B. Cebik (SK), who was a highly regarded "guru" on antennas, can work very
well, but will test the capabilities of your tuner on 80 meters. Also,
comparing the Gap Titan to the R8 was something done quite extensively by
Ward Silver, N0AX, who is well known for his expertise. Overall, the R8 was
the better antenna, but it does not cover 80 meters. If you look around,
you might find a good used one of either model, and save a bunch of bucks!
A lot of people will tell you that nothing beats resonant dipoles. They are
probably right. However, you may not be blessed with lots of space or other
important aspects necessary for having such, so a single dipole and balanced
line, and a good tuner, can make up for a lot of sins. The balanced feed
line will help you keep your efficiency up when multi-banding so long as you
have a tuner to do the matching. Using coax on such a system will introduce
significant loss unless the matching is all done at the feed point.
Otherwise, you might see a decent SWR, but your output will be significantly
reduced.
Hope you are not totally confused by all of this. Just remember that your
antenna is an extremely important part of your overall system, and needs a
lot of consideration and effort to really enhance your results. You have a
very nice radio, but it won't do much unless you put a decent antenna on the
end of it.
Dave W7AQK
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