I just completed constructing a F12 C4XL.
The antenna went together really well. The instructions were pretty
straight forward. Riveting the elements was fun and not hard to do. The
elements were all well marked, pre-drilled for the rivets and telescoped
for easy to assemble.
I assembled all of the elements and the boom in my driveway and then
carried everything up to my roof. The roof is only slightly sloped so
its perfect for assembling beams. I used three plastic/foldedable saw
horses which I layed out and assembled the boom on. Then I added the C3
and C4 elements, the C4 40 meter "spreaders", and after a little head
scratching (the photos in the assembly manual were hard to read) the
Aluma-weld wire and the linear loading elements for the 40 m elements.
On the 40 m reflector I snapped two of the Aluma-Weld 40 m elements
connecting them to the spreader. I called F12, and they sent me a free
set of replacements via 2nd day air so I had a few extra days of
Using the MFJ analyzer I checked the VSWR on the C3 portion of the beam
and all of the VSWR was 1:1 or 1:2...right on the frequencies where I
want to operate. The C4 portion of the beam took a little time to "tune
and prune" . Tuning which consists of setting the linear loading
elements per the manual and the adjusting them for the frequency you
want. The frequency as per the book setting where I found unity was 6.3
mHz., a little out of band even for KH6 ! It took less than an hour to
adjust the linear loading elements and the hair pin matching coil until
I found a 1:1 reading at 7.1 mHz. I painted the boom with a very light
blue paint and then with spray cans of green, grey and sand, camoflaged
it to look like my Hawaiian hillside of Hale Koa scrub.
The beam goes up next week on the 50' pirod tower (two -20' sections and
a 10 foot mast) and will be turned by a Hygain HDR-300, a bit over kill,
but I live on a steeply sloping hillside on the "Windward" side on the
island of Oahu and this is hurricane country. Serious on-air testing
and comparison to my super quite trap dipole and ancient TA-33 jr.
next weekend. This has been a fun project!
73's and Aloha,
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