D-I-Y VHF Comm antenna for Hangar
First, let me say right up front that this antenna was NOT my
original idea. I'd been looking for a good antenna for the
hangar, but had some specific requirements, and ran across a
couple of sites related to this antenna design.
Here's the web link that this whole project is built on: http://vk2zoi.com/articles/half-wave-flower-pot/.
And then a forum discussion Here
in relation to it. You'll find that first link has great
pics and info about the antenna.
My requirement wasn't that I'd have absolutely the best
range. I just didn't like the horrible reception I get in
the hangar with the door down, and wanted a good external
antenna. I didn't want one mounted on the roof, either,
because then I have even more worry about lightning
protection. This one is much less likely to get struck,
being below the roof line and tight to the building. The
bracket is just a piece of angle bolted to my door rail, and a bit
of flat stock bent out to another piece of angle that the antenna
is worm-drive hose clamped to. The result is that the
reception in the hangar on my scanner is much better and I can now
near people in the pattern and even in the pattern at another
airport 15 miles away with good clarity.
I think the design on that website was more of a HAM radio
antenna, so the lengths are a little different based on wanting to
use the Aircraft band. The forum I think discussed that a
little. The other change I made was that this was talking
about using PVC of 25mm, 32mm and 50mm in size, and gives a number
of coil turns. Well, I wasn't sure if when you wrap the coax
on the PVC if you really care about the diameter of the center
conductor, or the ID of the coil that is really based on the
outside insulation of the RG58. So I think I compensated a
little for the extra diameter of the actual center
conductor. I also think I added a turn on the coils to give
the right frequency. I did NOT test this antenna with an SWR meter
or anything, to prove that my changes were good or bad, so if you
build one, use your best judgement and if performance is a
big deal, experiment and make yours perfect. All I can say
is, I'm happy with how this one came out. The design is
nice, and not too obtrusive.
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