As per Fred Olver's request here is a repost of Part 1. The repost of part 2
will follow.
73, Jim, KY2D
-----Original Message-----
From: Jim Kutsch, KY2D [mailto:[log in to unmask]]
Sent: Wednesday, April 22, 2015 8:09 AM
To: [log in to unmask]
Subject: Hex Beam and accessible rotor, part 1: the hex beam
Howard and all,
In answer to your question about my hex beam and to add to the accessible
rotor discussion, I'll explain my setup. This will be in three parts. Part 1
is about the hex beam itself. Part 2 will describe the mast I used and how I
mounted it without guys. Finally, part 3 will describe the modifications I
made to a Ham IV rotor control to allow accessibility and also automated
control from the PC with an interface to ACLog. Here's part 1: the hex beam:
The Hex Beam that I bought is the K4KIO Hex Beam. Of the three major brands,
this is the intermediate price point. It comes in kit form in two boxes.
Everything is pre-cut, pre-measured, and connectorized.
As has been described here before by others, the hex beam looks like an
umbrella turned inside out. It consists of a base plate with about a 4 foot
vertical square piece of metal rising up from the center of the base. This
vertical piece becomes the center insulator for the driven elements
described later. Around the base plate are six fiberglass rods that are
called spreaders. Ropes are used to run from the end of each spreader to the
top of the vertical piece. These bend the fiberglass rods upward such that
the ends of the rods are at the same height as the top of the vertical
piece. Essentially, it makes a bowl shape with the vertical piece in the
center.
The simplest form of a hex beam is a single band hex beam. The antenna
itself is a two element beam. The driven element is a dipole made of two
pieces of wire with the center attached to the vertical piece in the center
of the hex beam. The driven element wires come out to the ends of two
spreaders then bend back towards the ends of the next two spreaders.
Essentially, when viewed from above, the driven element looks like the print
letter W. The reflector is another piece of wire that curves around the
back of the beam using the remaining spreaders to support it. When viewed
from above, the reflector looks like the print letter C. The driven element
and reflector are made up of one continuous piece of wire and rope in
combination. It starts with a wire that is half the length of the driven
element, connected to a piece of insulating rope, then that is connected to
another wire that is the length of the reflector, then that is connected to
another insulating rope, then connected to a wire that is the second half of
the driven element. By constructing these wire/rope combinations first, the
antenna is put together by attaching the end of the wire (which is the
center of the driven element) to the center vertical, bringing it out to the
end of one spreader, then bringing it around all of the remaining spreaders,
then bringing it back to attach on the other side of the vertical piece. The
K4KIO Hex Beam has pre-installed wire clips on each spreader so you just
need to thread the wire/rope around through all of the clips.
The spreaders have to be long enough to support the elements for the lowest
band you want to operate. For 20 meters, it's about 21 feet in diameter. The
20 meter elements are mounted at the ends of the spreaders where the
circumference is greatest. Additional bands can be added by using shorter
versions of the wire, rope, wire, rope, wire combination and mounting them
to the fiberglass spreaders at lower points where the circumference is
smaller. The K4KIO Hex Beams can have up to 6 bands. I ordered mine with all
bands: 20, 17,15, 12, 10, and 6 meters. Again, all of the wire clips were
pre-mounted at the appropriate locations on the spreaders.
If you want to read a lot about the construction and theory of the hex beam,
there are great articles in the "hex ed" section of the K4KIIO website at
http://www.k4kio.com/
Leo, K4KIO does a great job of sending you all you need in kit form. He
builds all of the elements, attaches the tie points on the spreaders for the
elements, and tests everything before shipping it. It is possible to
assemble the kit without sight. I'm totally blind and built mine once I had
someone read the labels to know which element was which but thinking about
it, I could have just unwound the wire and arranged the wires longest to
shortest and figured it out without help.
I built it with the base lying flat on the driveway. Then I put it at about
4 feet above ground sitting on a pipe put through the umbrella hole in our
patio table. That way the dogs wouldn't run through it and get snagged on
the wires. But, I couldn't wait to try it so connected it to the rig from
the patio table. Due to a late start and a very bad winter here in NJ, I
ended up using it that way for almost 5 months. It worked better than my
Carolina Windom even at only 4 feet but the coax got caught in the snow
thrower and I had to cut it out and buy new coax. Last Thursday, I put it up
on a mast. Now it's at about 20 feet. Since Thursday, I have worked 6 new
countries and I'm only running 100 Watts from an Elecraft KX3 with the
KXPA100 amp.
The hex beam is not very narrow so you don't have to aim it accurately. It
does have a really good front to back ratio and the noise floor is much
lower than with my Carolina Windham.
I'll describe the mast and mounting in a subsequent post Overall, I'm very
pleased. I had a 3 element triband TA33 Junior and a full TA33 in the past
at a different QTH and this hex beam seems comparable. In addition, it has
17, 12, and 6 meters which I didn't have with the TA33.
73, Jim
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