On 12/9/2011 2:06 AM, Jim Brown wrote:
> On 12/8/2011 9:23 PM, Keith Carter wrote:
>> The way I have done this for vertical yagis is to use two metal angle
>> brackets spaced about 2 to 3 feet apart off the side of the tower.
>> Then use a fiberglass pole about 4 feet long (available at most
>> hamfest as military antenna mast sections)
> Several guys have suggested some variation of this approach. It seems to
> make good sense to me, and is what I'll probably do. What I'm looking
> for now is suggestions about those stand-off brackets.
You could do it as a swing arm mounted off the face of the tower. IE any
side with two legs, rather than just one although the one would give you
more rotation.
Variations of this can be used for one of two legs. For one leg
attachment the mount forms a right triangle with the base at right
angles to the tower. The tower forms the vertical (up or down) part and
the angle from the outer end of the base to the tower forms the
hypotenuse. The base and hypotenuse mount to the tower using u-bolts,
or saddle clamps. You could also use a piece of angle iron or flat
plate maybe an 1.8" thick at this point. You can adjust the triangle
some so a pipe is either welded or bolted to the outer end of the base
and junction of the hypotenuse. The rotator mounts on this. The top
end of the mount(second mount) has a pipe attached to it for the
insulated mast or rod. Depending on the wind load a third triangle
could be mounted just above the rotator to prevent flexing. The antenna
would mount roughly half way between the top and bottom mounts with the
coax routed off the back end of the antenna and looped around to the
tower below. With a long boom antenna it's unlikely you will be able to
mount it far enough from the tower to get much more than 60 to maybe 90
degrees rotation, but at the limits the antenna elements would be so
close to the tower they would interact with it.
Without being able to draw the mounts this is about the best explanation
I can give.
I do have some drawing and drafting programs some where so I might be
able to come up with something a bit more concrete and pictorially
complete, but it might take a while.
73
Roger (K8RI)
>
> Many thanks to all who have contributed a bunch of good ideas. This
> list is a great resource!
>
> 73, Jim K9YC
>
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