In this case, I was
browsing the Internet for better antenna options and kept running
across articles expounding the virtues of the “Hexbeam Antenna”
and thinking, “Yeah, I could do that” so off I went.
Like many others, I
thought I might be able to get by with materials laying about the
house or readily available in my small town stores. After trying
numerous versions of PVC pipe and fiberglass rods, I wisely decided
that the fiberglass tubes suggested would be the better options. So
swallowing the little bit of pride available, I ordered the kit of
tubing (plus an extra piece of 3/4” , more on that later).
Whilst waiting for
the tubing to arrive I set out to collect whatever else I could
locate about the house. The aluminum plate was the first treasure
found. It was just a piece of 5mm painted aluminum that fortunately
seemed to good to turn in for scrap in the past. It took about an
hour with the bandsaw and hand drill to convert my former scrap
aluminum to a nice, 6-sided, base plate. I drilled the holes for the
U-bolts since I had also found a box of nice stainless ones that had
been ordered from China via Ebay for another antenna project. The
center hub was still a missing piece so that was left blank.
I thought that I had
plenty of stainless hose clamps, but a quick inventory revealed that
while I did have a bunch, the hexbeam was going to require many more.
OK, fine. But going to the local hardware was going to quickly burn
through the budget...so back to Ebay. Lucky me, I found a US vendor
selling quantities of 20 all-stainless clamps for two bits each.
That works.
Still no hubs, but
while I was on an XYL errand in my rural village I wandered into the
local pool supply store. I don’t have a pool but it was close to
the farm supply where I was sent to procure dog food. As I was
leaving, I spotted an old pool ladder behind the store. Can’t
resist a closer look... yeah, I like junk. The little aluminum feet
at the bottom of the ladder might just make the sought after hubs.
$5 made me and the pool guy both happy. I got them both, thinking
that one top and one bottom of the antenna base plate might be a good
idea.
My table saw (a
makeshift work surface) was now covered with a small pile of
potential hexbeam antenna components. One lucky find was a spool of
really nice black Dyneema rope. The stuff is ridiculously strong and
UV resistant. There were also a few spools of 14AWG THNN wire in
various colors. I had in mind that I would use some epoxy glue at
some point so I set out to locate what I might have, and to see what
sort of spray paint I might have that would still come out of the
can.
In the middle of the
search, the UPS truck pulls up the driveway with the precious
fiberglass tube kit. Nothing to do now but get to work.
The hose clamps
haven’t arrived as yet so I thought I would try out my original
plan A. That is, rather than slitting and clamping the sections of
tubing together, I would mix a bit of epoxy and glue each joint. The
found epoxy was the fast setting JB weld. It is easy to use and
plenty strong. I built one arm complete to evaluate the process.
Satisfied, I assembled the two smaller tubes of each arm and after
they cured for 20min, added the 1” tube. Lastly, I cut the extra
piece of 3/4” into 6 equal pieces and glued them flush into the
open end of the 1” end of each of the arms. The thinking here is
to make the ends a bit stronger to resist being crushed by the
U-bolts.
The next morning
there was nothing to do but to assemble the beast. I tried working
on the ground but my back was having no part of that. A recycle bin
was the only work table in sight, so be it.
The arms went on the
base in minutes producing a satisfyingly large representation of my
efforts so far. “Hmmm, what should be the next step” and: “Oh
S**t”, the center post! I had thought about it but somehow
neglected to build it. Narrowly avoiding another trip the the local
hardware store, an hour of searching produced the 1” square
aluminum extrusion that I had briefly envisioned for the post.
There are thankfully
good instructions on various websites that suggest ways to build a
center post. I drilled holes at the suggested locations and
fabricated 6 sets of PTFE shoulder washers. I wanted a copper center
conductor but all I could dig up was a bit of bare 12awg wire. Guess
that will work… so I laid the post on the bench (tablesaw), stuck
the shoulder washers in the outside, and poked in some #8
brass bolts. It took a little blue tape to hold everything in place.
The copper wire then soldered fairly nicely in the slotted heads of
the brass bolts. It took a bit of fiddling to get the ground bolts
in place but the big holes for the shoulder washers made it possible.
It was surprisingly easy to then shove the wire/bolt assembly down
the end of the tube and pull the bolts through the holes. Installing
the SO-239 connector on the side of the top was a bit more of an
effort but having done that I covered the open top with a bit of
scrap aluminum and some silicone.
Finally, now back to
the assembly. The post was a bit small for the pool ladder flange,
but wrapping it in a bit of scrap aluminum solved that little issue
and it tightened up nicely with the flange set screw.
I cut 6 eleven foot
(plus about 2”) pieces of the wonderful Dyneema line and
crimped/epoxied ring lugs on one end and made loops on the other.
Using a flame to cut the line left a nice little ball on the end that
further strengthened the crimp connection. The loops were also made
with crimps of copper tubing and a bit of epoxy. And all joints
covered with heat shrink just to make them look nice (like anyone
would ever see them).
And like the above,
I made another 6 eleven foot lines with loops on both ends to go
between the arms.
It took maybe 20
minutes to string the whole thing together. And 10 minutes of that
was searching for one of the line that was inadvertently sling
shotted into the weeds when I lost my grip on the end.
Time to stand back
and admire the new umbrella frame that now occupied most of my
driveway. It was like a really big “cat’s cradle”. A real
thing of beauty. I had a 4 foot piece of fiberglass post that was
part of a military field antenna mast so I put that into service as
the bottom post, primarily because it was a perfect fit to the pool
ladder flange. The XYL was not so amused at this point so I busied
myself with making the wire elements.
I was now practiced
in using the Dyneema line so I used that as the spacer between the
active elements and the reflector wires. Bending the 12 gage wire
into a hook, tinning it, and then laying in the line (with a little
ball on the end) in the crux of the hook was perfect. Smashing the
hook tight, adding a dab of epoxy, and then covering with adhesive
lined heatshrink, made for a super strong but very slim connection.
It took the rest of
the day to create all six band wire antenna elements. This is
probably the most time-consuming activity of the whole project. So
it was the next morning before I could begin stringing the enormous
spider web that was the current object of my wife’s complaints (her
car was going nowhere until this thing was somewhere else).
I had tested a
couple of methods for securing the wires to the arms using the
suggested hose clamps, and settled upon using a bit of aluminum strap
under the clamp, and about 2 inches of irrigation tubing around the
wire. The 20 meter loop went on first, where I quickly discovered
that it was annoyingly in the way as I worked on the rest. So the 6
meter went on next and worked outward from there. It really looks
like the Internet pictures now.
It took a few hours
with my budget antenna analyzer to correct a couple of lengths and
get everything tightened up. I couldn’t resist hooking up the
radio and made one contact on 20m even though the antenna was still
sitting at only 4 feet above ground. That done, I managed to get
I emptied out 4 cans
of miscellaneous spray paint that I thought might prolong the life of
the fiberglass and wires in the harsh California sun. To complete
the antenna I constructed a quick balun consisting of a 7 turn coil
of coax wound neatly inside of a piece of plastic sewer pipe.
I had a week to
admire my creation and to rebuild an old Yaesu 450 rotor (another
blog) before my son was able to come to the house so that we could
attempt to install the giant umbrella on my homemade tower.
Getting a 22 foot
diameter spider web to the top of a tower is no small task. It is
not particularly heavy, something around 25 lbs, but it is difficult
to find a place to grab the wiggly thing. We managed to sort of
slide it up one of the tower guy wires by pulling it with a rope: my
son at the t
Just luck I’m
sure, but upon reflection, this project had far fewer mistakes and
retries that just about anything I can remember doing. It is hard to
say what it cost considering all of the material that was in the
various junk boxes but the outlay for new stuff was under $200. As
for performance, the hex pretty much lives up to the hype. I have
two dipoles and a skyloop for antennas in addition to the new
hexbeam. The hex is much better at rejecting local noise (from the
neighbors solar panels I think) and being directional has really
helped in catching the attention of some fairly distant DX stations.
It also catches the attention of the neighbors but no complaints as
yet. It would have been nice if it could have covered 40 meters, but
that would never have made it to the top of the tower.
Many thanks to those
whose contributions to the websites make projects like this one
possible.
