At 10:11 AM 7/28/2005, ersmar@comcast.net wrote:
>TT:
>
> Good solution, but guying may be needed depending on antenna load
> (2M Yagi vs HF dipole wires vs UHF vertical.) Concrete blocks could be
> used as anchors at guy points in parking lots. Be sure you clearly mark
> the blocks, if used, as pedestrian hazards.
>
>73 de
>Gene Smar AD3F
>
> > ----- Original Message -----
> > From: "Matt Patterson"
> >
> > > This thing would be super easy to homebrew...
> > >
> > > Then purchase one of those fiberglass masts you see on ebay all the time.
> > >
> > http://www.qsl.net/wb3gck/mast_support.htm
> >
> > Not as fancy, but still workable...
> > And AOL Ham keyword: CHEAP/EASY to do....
> >
In all but the lightest of winds, guying is almost certainly needed, unless
you're willing to tolerate a mast failure. In lots of portable type ops,
though, having the mast come down (or bend) if a big gust comes up is a
perfectly acceptable way to operate.
I did some analysis on using a car to stabilize a vertical mast with
windloading. I wanted to see if it would rip the rack off the car, for
instance.
http://home.earthlink.net/~w6rmk/antenna/mastcar.htm
The calculations were fairly conservative (large mast diameter, 50ft high,
80 mi/hr wind) but the forces get pretty big, pretty fast. A concrete
block isn't going to hold a 20 pound load without dragging, and even in a
40 mi/hr wind, you only need about 5 sq ft of total area to drag the block
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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