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This is an outdated standard.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" <n6sj@earthlink.net>
To: "Tony" <73guddx@gmail.com>, "towertalk" <TowerTalk@contesting.com>
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 <towertalk-bounces@contesting.com> 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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