I think one reason for the variations is that standards (calculations)
have changed over time (thank the lawyers?) In 1971, I put up a Heights
72' aluminum tower. It required a 4'x4'x4' concrete base. No mention of
concrete strength or rebar requirements. I literally hand mixed the
concrete over two days in a wheelbarrow, one shovel of cement, two of sand,
three of gravel. It was rated for at least 10 sq ft. Now the same tower
requires a sonotube hole, 3.5' in diameter by 7.5' deep with a welded rebar
cage. They say the sootube isn't necessary if you don't mind pouring an
additional 2 or 3 yards of concrete!
We had an online discussion about tower failures a few years ago. It seems
that almost all failures are 20-30' above ground, few or none fail by the
base being insufficient.
We get some high winds here. I couldn't dig my base deep enough for my
current tower (Rohn HBX-56), I hit bedrock at 40". I'm not worried about
it. YMMV.
Ken WA8JXM
On Sun, Feb 18, 2024 at 4:02 PM Dave . <ktx85@hotmail.com> wrote:
>
> Wow....
>
> I live in central Iowa.....Originally was planning on a US tower
> Hdx70 tower but it was destroyed in bad weather before I could
> purchase....so this Hy Gain tower became avaliable..I thought I could use
> this for now until I got a 70 replacement...but
>
> Confusion ...
>
> I was looking up a HyGain hg54HD
> IN one factory document I see 16sq ft at 60mph (1990)
>
> In annother factory calculations document I see 25sq ft
>
> I know these calculations are from days of old
>
> And other mfg numbers are ALL over the place
> And let's not forget that many of the antenna mfg windload numbers are
> well...I'm not sure what to call them
>
> Here is the plan
>
> HY-54GD....16sq....supports ?
>
> Concrete base for tower is rated for a HDX70 ( 2 x more Concrete than the
> hy54hd requires)
>
> For comparison
>
> Hdx555 23 Sq. Supports 200lbs
>
> nn4zz tiltplate......1sq. 30lbs
>
> Steppir 4 El 40-6....( 1 trombone)........18.5 Sq. PROJECTED ??? A few
> sites say 12sq......106lbs
>
> 3 .....M2. 2m12 2m yagi. 1.5 Sq each. 8lbs each
>
> 1 wire dipole......
>
> 1 diamond x510HMN..........
>
> Yaesu 2800 rotator...14.33 lbs
>
> 2 inch 1/4 wall 6063 alum mast...4 1/2 foot above the Tilt plate...Tilt
> plate 2 inches above thrust bearing
>
>
> Looks like my wind load with all the above would be 23.5 sq....OOPS...
>
> OBVIOUSLY...I wouldn't leave the tower up in a 60mph wind.( that's asking
> for trouble)
>
> It is 22ft cranked all the way down.....
>
>
> It seems as if you want more than a dipole on top you have to purchase a
> 80,000 tower
>
> Are there numbers SOMEWHERE that are "real" .?
>
> Every mfg seems to have their own calculator..
>
> M2 antennas and nn4zz seem reasonable
>
> It appears all numbers are cover your butt numbers the mfg have come up
> with...
>
> There are so many years and years of politics in between. And
> calculators....
>
>
> And to say hams NEVER overload their towers....well...that would be a
> fairytale
>
>
> Is there some rule of thumb that this might work to say 30-40 mph without
> cranking down?....is there someone with a simular set up that is in use
> that can share some thoughts ?
>
> Sigh
>
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>
>
>
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