Recent post on here inquired as to "understacking" ...
Been there, done that, worked very well ... Using ALL store bought
materials (ie NO welding/rigging...) ... and had NO problems ...
I found the article in HAM RADIO magazine, June 1980 pages 62-66 by
Robert Myers W1XT (yes, the Gladiator Antenna Man !) He added via
"understacking" a 5 element 24' boom 10m yagi under a Mosley S-402
2 element 'shorty-forty'. Dig out the article for more details as
he provided a great deal of detail/pictures/information to go by.
I used the idea with a Cushcraft 40-2CD 10' "under" a Wilson System
One tribander and it worked very well. It ALL bolted together and
was installed by hauling one piece up at a time, no cutting or any
welding was required to make it all work. I do however suggest a
'dry run' ON THE GROUND and premarking as to save time and avoid any
confusion in the air !
When installed, the "understack" mast cleared the tower by about 8"
to 10" and I had NO problems with the lower end of the mast EVER hitting
the tower in high wind gusts/etc. It was very KISS and worked. I had
an extra 2" clamp at the top of the 2" mast, and at the bottom, just
to ensure that the mast did not slip out of the "Z" nor could the 40m
yagi 'slip off the end' when being installed.
Here's what I used:
2" SS U-bolts/saddles/washers/etc via Mosley (as used on a CL36)
10'x2"x0.125" wall Rohn M200H HD galvanized mast (don't use water pipe)
1 "Z" from IIX Equipment (it's the SWINGARM part of his sidemount
setup)
When I removed the "understack hardware" to put the 40m yagi on it's
own TIC rotor, the hardware ALL looked just as I had installed it 6
years earlier. I plan to re-install it again soon on another tower.
Do it right the first time and use quality materials and you'll spend
more time ON THE AIR using it, not IN THE AIR fixing it !
Hope this information proves useful to someone !
73 Billy AA4NU aa4nu@ix.netcom.com
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|