Something else to consider is whether the limit is "no appreciable effect" or
"some damage" or "catastrophic failure".
Hams can usually tolerate some damage, as long as nobody gets hurt and no
structures are significantly damaged. Permitting authorities sometimes have a
different viewpoint, as do people designing commercial facilities.
(sort of the R56 compliance debate in a different form - keep operating vs
tolerate lightning damage vs don't start a fire).
On a telescoping tower, if it's up, and the wind comes up, what if the lowering
mechanism fails, or is unable to be operated? The tower might be damaged (and
might even "stick" in the extended position), but that might be tolerable.
Or, "lower when high winds forecast" - forecasts aren't perfect. maybe you
aren't there to lower.
all these sorts of things go into a "systems engineering" kind of analysis,
beyond the "what is the structure good for"
On Tue, 6 Jan 2026 19:38:38 -0800, "Steve Jones" <n6sj@earthlink.net> wrote:
Bruce, good point on #4, exposure: Remigio told me if there are trees
around the tower, that really helps break up the wind. Mine is enmeshed in
a forest of Douglas fir trees! Nad below the top of the ridge, not on top.
73,
Steve
-----Original Message-----
From: TowerTalk On Behalf Of Bruce Horn
Sent: Tuesday, January 6, 2026 5:49 PM
To: towertalk
Subject: Re: [TowerTalk] US Tower Weight / Wind Load Load Limits
Hi,
I have a UST HDX-589 with a SteppIR DB36 at the top of a mast (potentially
105 ft level) and a Optibeam 16-3 side mounted at the 72 foot level.
However, I know these antennas exceed the engineering ratings for the tower
and therefore seldom crank the tower all the way up - the top antenna is
kept at about the 70 foot level, which results in overlap of multiple tower
sections. It's been up now for more than 30 years with various antenna
configurations and the only failure I've had is a broken rotator, but I live
in an area with relatively little wind.
Some things to consider:
1 - US Tower's engineering calcs show that it was calculated based on
TIA-222F. This is an outdated standard. The move to TIA-222G resulted in
significantly lower ratings for the same tower design. And now it appears
the most recent standard is 222I.
2 - the antenna windload specified by the manufacturer may have been
calculated using a different standard than the tower. The OB 16-3 has a
square cross-section boom and therefore has a greater windload than the same
antenna would have with a round boom.
3 - the calculated maximum tower load is for the entire load placed 1 foot
above the top of the tower. When you use a mast to place antennas at higher
levels, it derates the maximum wind load of the tower. You can't simply sum
the wind loads of the antennas.
4 - Tony, is your QTH in a windy area, or relatively calm area. On a ridge
top? Do other nearby structures/trees offer a wind break? All of these
factors influence to what degree you can live with professional engineering
limitations vs. the typical ham "engineering."
Good luck with your project. I like the OB 16-3 tribander.
73 de Bruce, WA7BNM (bhorn@hornucopia.com)
----- Original Message -----
From: "Steve Jones"
To: "Tony" <73guddx@gmail.com>, "towertalk"
Sent: Tuesday, January 6, 2026 3:53:53 PM
Subject: Re: [TowerTalk] US Tower Weight / Wind Load Load Limits
Tony,
When I put up my UST HDX-589 I spoke with Remigio Fernandez, their
structural engineer. I put a SteppIR DB42 on top at 90 feet. About 20+ sq
feet of wind load. Remigio said if the weather forecast is for 50 mph or
higher gusts, lower the tower! Otherwise it will be OK. I have done this
for about 13 years and it hasn't failed yet.
Happy New Year es 73,
Steve
N6SJ
-----Original Message-----
From: TowerTalk On Behalf Of Tony
Sent: Monday, January 5, 2026 3:11 PM
To: TowerTalk@contesting.com
Subject: [TowerTalk] US Tower Weight / Wind Load Load Limits
All:
I plan on replacing my HF antenna with an Optibeam model 16-3 Yagi. It's an
interlaced 4/4/8 element Yagi that covers 20/15/10 meters. The antenna
weighs 130lbs with a 33 foot boom with a wind rating of 12.7 sq. ft at 75
mph.
I also plan on adding an additional 6M and 2 meter Yagi's above the HF Yagi
on an 18-foot mast. The specs for the 6M / 2M antennas are 30lbs 30ft boom
and 16lbs 21 ft boom. Windload is 5 and 2 sq.ft. at 75mph.
The total weight in antennas comes to 176lbs with an estimated wind load of
18 sq.ft.
My tower is the HD555 heavy-duty model made by U.S. Tower. It has an antenna
weight limit of 200 lbs and a wind rating of 23.4 sq.ft at 75mph. The
rotator is the Yaesu 2800.
This setup "should" be within the towers rated limits, but I wanted to run
the numbers by the group since there's a lot of experienced folks on this
reflector.
Thanks, Tony -K2MO
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