Hi ...
Here's some other points to consider ...
I do all the antenna work with the team of me, myself, and I <grin>
All of the yagis here at AA4NU had/need/use some form of a
'boom brace or support' or similar thingi ...
For me the 'worst time' for a boom related failure is while
I am putting the yagi up, or taking it down.
The stock Cushcraft boom support is useless during those times.
For those of you who are using the 40-2CD on a 15ft HD mast, if
you put the stock boom braces on top, you loose a few feet of spacing
between it and the lower antenna .... going under the boom 'works' as some
have cited, but it's not as effective as on top, so now you sit and wonder
"just how well" does it work every time your wind hits a new record gust.
My solution for the 40-2CD was to copy the method that Wilson (and
others ?) used for their antennas. Build a vertical upright/outrigger that
bolts ON the 40-2CD boom. I used the stock CC braces for many years,
but for their size/weight did not seem that effective and I changed to a
typical guy wire with small eyebolts that looks "3 dB better and seems
stronger" ... I can raise or lower the 40-2CD without worrying about
the stock boom sagging as it does without any support. I can adjust
the boom before I haul it up to it's mount without any strain on me !
The long CC braces are not in the way now as they were before.
The vertical upright can be as simple as a 1" piece of aluminum angle
about 24" - 36" long .... Drilled at the bottom for a U-bolt/saddle that
goes
around the 40-2CD's boom (and remember that the boom is BIGGER
than 2" at the center!) and then two holes are drilled at the top for the
eyebolts. The boom end can be made out of similar stock, about 3"- 4"
and drilled for the 2" U-bolts/saddle and one hole for the eyebolts. I use
stainless hardware where I can and plated where I could not find any
SS. The eyebolts give you plenty of adjustment to trim the boom up.
A perfectionist would most likely use Phillystrand for the support wire. I
used some old 3/16" from a previous installation. Most of the parts
I found by digging through my antenna junkbox ...
Now you can put that 40-2CD at the top of your HD mast and have
the most spacing possible to minimize the interaction concerns ...
(You did figure the wind loading and mast/tower moments, right ?)
W6NL (x-W6QHS)and also N4KG have written various texts on improving
the 40-2CD's wind survival rate. W9RE offers a "kit" with the parts. A
better
route to take would be one of those methods if you really want to solve the
boom support problem and improve the 40-2CD's possible few weak spots.
Nope, I'm not an engineer (tho I play as one in my own backyard) so your
"RF mileage" may vary ... GL !
73 Billy AA4NU
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