Gene Smar wrote:
> In a self-supporting tower, all the overturning moment is applied at the
> concrete base. For my short (64-foot) tower and its modest HF Yagi load I
> constructed a base of 10.5 cuyd of 3500 PSI concrete with rebar, per Trylon
> For a house-bracketed tower, this overturning moment is applied to the
> bracket, its mounting hardware and the house structure. (Because the rigid
> fastening (bracket) is higher above ground than a SS tower, this force would
> be lower than on a SS tower.) You can see why using a couple of half-inch lag
> bolts into the siding and wood sheathing of a typical residential
> installation may not generate enough holding force to keep from pulling out
> in high winds. That's why using a house bracket requires a bit more
> engineering than we have been discussing here on TT.
And why the wood walls of many homes are not sufficient without
modification to hold a tower bracket.
OTOH at one time ROHN made a dirt base and I believe they still make the
drive rods. If the soil is of the proper quality I'd have not problem
using a dirt base under a 30' bracketed 25G holding a couple of UHF and
VHF antennas or even a small tribander.
> For more info on the subject of house brackets for towers check out the
> 8/96 QST article by K1KP. Good luck with your study/project.
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