On 2015-02-12 2:00 PM, n8de@thepoint.net wrote:
>
A free-standing Universal aluminum tower composed of 26" tapered,
22" tapered, and 18" topper will support ANY common
tribander/vertical/VHF combo presently being used in ham radio.
While that may be true in Michigan where the wind requirements are not
particularly high (70 MPH rev F, 90 MPH Rev G), that may not be true in
Seminole County, Florida where the building requirements are for 140
MPH (139) wind speed.
Note the force due to wind is *2.5 times higher* at 140 MPH than at
90 MPH. Directly comparing the allowable antenna in Rohn's example
designs for 90 and 130 MPH indicates the same tower will support
less than half as much antenna 1t 130 MPH as it will support at 90
MPH.
Universal Towers does not even give windload data for 140 MPH on their
web site (they provide spec's at 80, 100 and 110 MPH for the light duty
towers but nothing for the heavy duty models) but given the nearly
constant winds in Seminole County, FL, I would *never* trust one of
their towers as I've seen how badly their bolted connections "egg
out" after only a few years in the much more calm areas of the Great
Lakes region.
73,
... Joe, W4TV
On 2015-02-12 2:00 PM, n8de@thepoint.net wrote:
Unless he is intending to put up a stack of huge monobanders and/or
SteppIR yagis, he doesn't need the 30" sections.
A free-standing Universal aluminum tower composed of 26" tapered, 22"
tapered, and 18" topper will support ANY common tribander/vertical/VHF
combo presently being used in ham radio.
Do the research ... I have 3 Universal towers up now ... and plan to put
up 4 more soon.
73
Don
N8DE
Quoting Gedas <w8bya@mchsi.com>:
Brian, I would not rule out a free standing tower esp since you need to
stay under 30'.
I have several self-supporting Universal towers here, each of which
uses as their first 3 sections, their 30" HD series sections. When
assembling the towers and after getting those first 3 sections up in
the air, you realize how strong that structure is.
In your case, since you mentioned 24', I would use two 30" HD sections.
See if you can get the top section modified either by Universal or by
a local welding/fab place to make it a topper with a collar where you
can then use a 2" or 2.5" mast. My gut tells me that two 30" HD
sections with a 4'-5' mast will still be standing long after your home
is leveled from some severe wind storm.
Gedas, W8BYA
Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 2/12/2015 1:03 PM, Brian Carling wrote:
Many thanks Bud.
I will need to review which version they are using. Yes I had
someone pointing me in the direction of a freestanding tower but I
think I may go to using guys.
It's either that or trade my tower sections in on a stronger better
built freestanding tower designed for that purpose. I only need
about 24 to 28 feet in height. Maximum.
Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773
Tel: +USA 321-262-5471
On Feb 12, 2015, at 12:27 PM, W2RU - Bud Hippisley
<W2RU@frontiernet.net> wrote:
On Feb 12, 2015, at 9:58 10AM, bcarling@cfl.rr.com wrote:
I am putting together a permit application with my city which
requires certfication for 139 mph
for three second gusts as in TI-222 spec. Also steady 100 or 110
mph I think.
We are making a 30 foot Rohn 25G tower according to the Rohn
specification with 4 foot
cube base of concrete with no guys.
I?m not sure I understand what you?re hoping to find.
My 4-year old Rohn catalog makes it VERY clear that 30 feet of Rohn
25 can hold only 1.7 sq. ft. of added antenna when the environment
is 90 mph (ANSI/EIA-222 Rev. E) and NO ICE. (For areas that
experience icing, Rohn 25 is specified by the manufacturer at ZERO
sq. ft. of additional antenna load!) From your e-mail address and
the wind speeds you mention, I?m going to guess you?re in Central
Florida, and I daresay a 90-mph Rohn EIA-222 Rev. E specification
is not going to be adequate for your city.
Nowhere in your posting do you mention what total antenna, rotator,
feedline, etc. wind surface area or wind load you anticipate
putting on this tower. But my guess is that NO freestanding 30?
Rohn 25 tower is going to make the grade.
Also, you fail to mention which version of TIA/EIA-222 your city is
using. The latest I?m aware of is Rev. G ? a substantial revision
from previous methods of specifying wind loading.
Bud, W2RU
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