In a message dated 2/25/2008 12:42:59 P.M. Pacific Standard Time,
> I have been looking at a number of options for a fairly light-weight,
free-standing (unguyed) tower (mast) with a counter-balanced tilt-over.
> The antenna(s) I am considering are simple and light-weight, either
> 1) a 20 meter wire Moxon, or
2) a 20 meter - (or 5 band) Hex-beam.
> The mast height would be between 25 and 30 feet.
> My QTH is on a high bluff about salt-water. The mast base would be at
about 100 ft elev. The ground then slopes very gently to the edge of
the bluff, which then drops almost vertically about 80 ft to the beach.
The distance from mast base to bluff is about 60-70 ft.
> For various reasons - esthetic and neighbors, and installation and
maintenance, I am looking at a low elevation, low visual impact antenna
with a tilt-over capability. Not a crank up. Not a "traditional"
looking lattice tower. I don't want to climb. I want to lay the tower
over for maintenance and wind (it can blow a lot here!) I have
considered the MA-40. I think it is over-kill for my situation. I also
don't like the tilt-over scheme - cable and winch.
> So, I considered a simple tilt-over. I have a DX Engineering vertical
tilt-over. It tilts from the base. The combined antenna/mast/modest
rotator would weigh about 25-30 lbs. Plus the weight of the mast. I
could "walk" it up or down without too much trouble. But, it seems to
me a counter-balanced scheme would be superior.
> I made up a simple drawing - you can find it here:
> _http://www.rbogash.com/Tower%20design.jpg_ (http://www
> The mast would normally be locked in the vertical position and lowered
for maintenance and wind events. However, I have also contemplated the
option of leaving it unlocked and "floating." In the event of a wind
storm, with say sustained winds of 50 and gusts to 75, the antenna/mast
might float to an angle - say 20 degrees off vertical in the sustained
wind, and, in effect, become "unloaded." When a 75 mph gust struck, the
mast would then really be seeing only a 25 mph delta increment.
First of all, the windspeed rating for Kitsap County is 85MPH. And wind
forces go up as the sum of the squares so your windloading on anything will
be reasonably significant. The MA-series UST is rated for about a 25# antenna
Your design might work for you but I'd run it by an engineer just to be
on the safe side.
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