Rohn 25, How many feet over last house bracket (un-guyed)
J.Swenson
possible. I have 2 house brackets. Someone said 30' over the last one
is ok. Is this right?
Robert Smits
Absolutely NOT! Rohn 25G is designed to be guyed. It is rated to carry 30
lbs./sq foot Wind load, with 6 sq ft of allowable load, but only when
guyed. Even the 40 foot tower has two sets of guys in the plans, at 20
feet and at 40 feet. If the top set are left out, the load should be
derated by 50 %, which won't include any 6 el HF antenna.
This info is taken from the Unarco Rohn catalog.
--
rsm...@ham.island.net (Robert Smits VE7HS)
Gary Coffman
>I would like to put up some Rohn-25 with a 6 element uagi without guys if
>possible. I have 2 house brackets. Someone said 30' over the last one
>is ok. Is this right?
No. Or rather it depends on the windloading of the antenna. If you're
talking about a little UHF yagi, then it's probably Ok, but if you are
talking about a 6 element 20 meter beam, not a chance.
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | emory!kd4nc!ke4zv!gary
534 Shannon Way | Guaranteed! | ga...@ke4zv.atl.ga.us
Lawrenceville, GA 30244 | |
Doug Snowden
: >is ok. Is this right?
: Absolutely NOT! Rohn 25G is designed to be guyed. It is rated to carry 30
: lbs./sq foot Wind load, with 6 sq ft of allowable load, but only when
: guyed. Even the 40 foot tower has two sets of guys in the plans, at 20
: feet and at 40 feet. If the top set are left out, the load should be
: derated by 50 %, which won't include any 6 el HF antenna.
: This info is taken from the Unarco Rohn catalog.
I am not an authority on this subject, but I am sure I have seen somewhere
that a Rohn 25 will support some sort of load up to 40ft unguyed. Of
course with a good base.
--
Doug Snowden
work: (407) 242-5542
home: (407) 98409360
dsno...@ccd.harris.com
Doug Faunt N6TQS +1-510-655-8604
used guyed, self-supporting, or bracketed"
Then there are various tables, such as this one, which is a partial:
25G bracketed tower
Tower Bracket Allowable antenna areas
Height upper lower 70mph 80mph 90mph
40 30 15 15.3 11.3 7.7
50 36 18 14.6 10.0 6.8
60 46 23 14.0 8.9 5.9
............
25G Self-supporting
Tower Allowable antenna areas
height 70mph 80mph 90mph
10 19.7 14.3 10.5
20 14.2 9.0 6.9
............
All of this information is available from Rohn, for an inordinate
amount of money, or from their dealers, FOR FREE. I had to push the
guys at my local HRO, with a letter in hand from Rohn stating the
above, but ended up with a complete technical manual for nothing.
73, doug
jbmitch
>
>I would like to put up some Rohn-25 with a 6 element uagi without guys if
>possible. I have 2 house brackets. Someone said 30' over the last one
>is ok. Is this right?
>
to be self-supporting providing a house bracket is used, and under normal
conditions the 25G can rise 35 feet above this bracket." Nonetheless, it
depends on the size of the antenna you're mounting. If it's 6 elements on
HF, like a TH6, or Pro-57, etc., I wouldn't be comfortable going more
than 10-15 feet above the highest house bracket. Consult professionals
in your area, such as commercial tower installers. Good luck and be
careful.
D.C. Henderson
: I would like to put up some Rohn-25 with a 6 element uagi without guys if
: is ok. Is this right?
I'm no0t sure what a "6 element uagi" is?? How many square feet of wind
loading??? I ran 40 feet of Rohn 25 unguyed with a house bracket at the
9' point, 3'x3'x5' concrete base, for over 10 years in Melbourne, FL.
Antenna was Cushcraft A4 tribander and a 7 element 2 meter beam. Survived
gusts estimated to 70 mph in heavy rain. I did put temporary guys on it
whenever a real hurricane came to town however. My guess is as long as
you stay below about 6 square feet of antenna you should be ok. By the way
you should always use temporary guys when working and climbing on the
thing !!!!!!
Contrary to an earlier posting Rohn does (or used too) rate the 25 series
to 30' without guys and to 40' with a house bracket and no guys. I don't
remember what the antenna wind loading was but it was less than 6 sq ft
I'm sure. If this 6 element uagi is a 6 element HF yagi then guy it or
get some rohn 45 (which is rated to 50' unguyed with a house bracket.)
Once the winds get above 75 MPH all bets are off! Guyed, unguyyed, laying
on the ground! Been there done that!
Dave
N0DH/7
Cliff Frescura
>In article <3rf6tn$n...@transfer.stratus.com>, "J.Swenson" <jswe...@jswenson.hqsl.stratus.com> says:
>>
>>possible. I have 2 house brackets. Someone said 30' over the last one
>>is ok. Is this right?
>>
>to be self-supporting providing a house bracket is used, and under normal
>conditions the 25G can rise 35 feet above this bracket." Nonetheless, it
>depends on the size of the antenna you're mounting. If it's 6 elements on
>HF, like a TH6, or Pro-57, etc., I wouldn't be comfortable going more
>than 10-15 feet above the highest house bracket. Consult professionals
>in your area, such as commercial tower installers. Good luck and be
>careful.
Here's what I know works:
Dig a hole in the ground, approx 1.5ft x 1.5ft x 6ft deep.
Fill the bottom 6 inches with pea gravel.
Insert one 25G straight section into the hole
(there is a top and bottom to each section ;-) )
Call the "mud" truck. You'll need about one yard.
Jog section in wet mud until it is vertical.
Wait about 1-2 weeks.
Add two straight sections and top section.
You now have a 35' tower (+/-).
I have a three element tribander on the top of this tower with no guys.
This installation survived hurricane Hugo (100mph winds). Though I could
see the tower sway a bit!
When I moved from NC to PA I disassembled the tower and hacksawed off
the bottom 5 feet. The base looked fine, both inside of the legs and
outside of the legs.
I put up a second tower using this same method and thought I would try
three staight sections and one top section. At the top of the 3rd
straight section I felt there was too much sway to think about adding the
top section and removed the third straight section.
This seems to fit the data in the Rohn Handbook.
Caveat Emptor:
I would not put any antenna on the tower that was more than a 3 element
tribander (A3S variety). I would never go higher than 35 feet. I would
only use NEW tower sections. The soil composition will determine what
you can do. The last two feet of the hole are the hardest. Don't stop.
Enter at your own risk.
73,
Cliff K3LL
--
+--------------------------------------------------------------------------+
|cl...@pgh.nauticom.net K3LL @ W3UDX.#WPA.PA.USA.NOAM |
| k3...@pgh.nauticom.net "Adapt, Migrate, or Die." |
Frank Donovan
U failed to mention what band this six element Yagi is for!
It makes a big difference if its a 20 meter 6 element Yagi!
The 1991 Rohn Catalog says "the Rohn 25G can rise 35 feet above this
bracket." This assumes u follow the requirementss in the Rohn drawing
for installation of bracketed towers and do not exceed the allowable
antenna area. In the example cited above, the allowable antnna area is only
1.7 sq ft at 70 mph (very few areas of the country are safe for only 70 mph
designs). If u reduce the tower height to 24 feet above the bracket u shud
be good for 6.8 sq ft at 70 mph, but only 4.9 sq ft at 80 mph. At 14 feet
above the bracket u start to be able to safely handle small HF tribanders:
13.5 sq ft at 70 mph, 8.3 sq ft at 80 mph and 5.5 sq ft at 90 mph. If
u reduce the height above the bracket to 10 feet, the antenna areas increase
to 15.3, 11.3 and 7.7 sq ft at 70,80 and 90 mph.
I strongly suggest u get urself a current Rohn catalog!
73!
Frank
W3LPL
Frank Donovan
since I have in my library a 68 page pamphlet published in 1990 entitled:
ROHN
25G, 45G
GUYED TOWERS
BRACKETED TOWERS
Enclosed in this brochure is: "Reference Sheet and Assembly Information,
#25 Bracketed Towers, Non-guyed" Sheet D-2524 dated March 1, 1989.
A similar sheet for Rohn 45 towers is also enclosed, as well as very detailed
engineering drawings on the installation of bracketed towers!
Bracketed towers require the use of a Concrete Base Section, Rohn p/n
SB25G5. Pinned bases must NOT be used.
Here is a quote from Sheet D-2524:
Bracket Positioning for 25G Tower
Tower Upper Lower Allowable Antenna area (sq ft) NO ICE
Height Bracket Bracket 70 MPH 80 MPH 90 MPH
40 30 15 15.3 11.3 7.7
50 36 18 14.6 10.0 6.8
60 46 23 14.0 8.9 5.9
70 56 28 13.5 8.3 5.5
80 66 33 13.1 7.7 5.0
90 66 33 6.8 4.9 -
100 66 33 1.7 - -
NOTES: All towers must have fixed bases, pinned bases must not be used.
Designs assume one 5/8" transmission line on each face (total=3)
symettrically placed. (allowable antenna load increases with
fewer transmission lines and/or smaller transmission lines - consult
Rohn).
Antennas and mounts placed symettrically at tower apex.
All allowable areas assume round antenna members.
For foundation details see Rohn drawing A871298
The structure supporting the tower bracket must be designed to
support a minimum horizontal force of 815 pounds
73!
Frank
W3LPL
On Sun, 11 Jun 1995, Robert Smits wrote:
> "J.Swenson" <jswe...@jswenson.hqsl.stratus.com> writes:
>
> >I would like to put up some Rohn-25 with a 6 element uagi without guys if
> >possible. I have 2 house brackets. Someone said 30' over the last one
> >is ok. Is this right?
> >
>
> Absolutely NOT! Rohn 25G is designed to be guyed. It is rated to carry 30
> lbs./sq foot Wind load, with 6 sq ft of allowable load, but only when
> guyed. Even the 40 foot tower has two sets of guys in the plans, at 20
> feet and at 40 feet. If the top set are left out, the load should be
> derated by 50 %, which won't include any 6 el HF antenna.
>
> This info is taken from the Unarco Rohn catalog.
>
Ron Klein
writes:
>
>: >I would like to put up some Rohn-25 with a 6 element uagi without guys if
>: >possible. I have 2 house brackets. Someone said 30' over the last one
>: >is ok. Is this right?
>: >
>
>: Absolutely NOT! Rohn 25G is designed to be guyed. It is rated to carry 30
>: lbs./sq foot Wind load, with 6 sq ft of allowable load, but only when
>: guyed. Even the 40 foot tower has two sets of guys in the plans, at 20
>: feet and at 40 feet. If the top set are left out, the load should be
>: derated by 50 %, which won't include any 6 el HF antenna.
>
>: This info is taken from the Unarco Rohn catalog.
>
>I am not an authority on this subject, but I am sure I have seen somewhere
>that a Rohn 25 will support some sort of load up to 40ft unguyed. Of
>course with a good base.
>
>--
>Doug Snowden
>work: (407) 242-5542
>home: (407) 98409360
>dsno...@ccd.harris.com
>
>
The Rohn 25 is NOT designed to be unguyed - if you meen as a freestanding
tower with no house bracket to support it.
I recently testified as an expert witness (I hold a PE license) in a case
involving just that question.
--
Ron Klein - W0OSK
-----------------
ronk...@ix.netcom.com
John Marcus
information! I bought a Rohn 25 tower. I have 50' of tower. My city states
I may erect a tower to a maximum of 65 feet without the use of guy wires, (for
safety), and withstand an 80mph wind!
I called Rohn, and they shipped me a very thick engineering manual. Their
book specifies that at about 30 feet, with up to about 10sq feet of windload,
I can withstand approximately an 80mph wind and survive freestanding. I don't
have that book handy, but I recommend calling Rohn. They were extremely
helpful. Most of Rohn's ratings were at a 50mph wind. They claim that at 40
feet, with around 10-14sq feet of loading, the tower will have no problem free
standing in the 50mph wind. I can't recall the locations for guying, but
there is a science to it so that there is a minimal twist to the tower in
strong wind.
House brackets work very well. I can't remember where the bracketing was to
take place, but I think it was every 20 feet. In any case, I don't think you
want to go more than 20 feet above a house bracket without additional guying.
If you want to contact me, I'll get the manual from home and look up your
requirements. Drop me an email at mar...@interaccess.com or call me at work
(800) 879-6137 x164 from out of 708 or 312 or call (708) 604-7164 directly in
my area.
Good luck, John - WD9AIS
In article <3s1ajn$q...@ixnews6.ix.netcom.com>
ronk...@ix.netcom.com (Ron Klein) writes:>From: ronk...@ix.netcom.com (Ron
Klein)>Subject: Re: Rohn 25, How many feet over last house bracket (un-guyed)
>Date: 18 Jun 1995 13:44:23 GMT
*********************************
|-------------------------------|
|John Marcus |
|Contact Info: |
| |
|mar...@interaccess.com |
|(800) 879-6137 x164 at work |
|(708) 604-7164 at work (direct)|
|_______________________________|
Milt Forsberg
is a Moseley TA-33 at the top and a 2m beam 10 ft above that. There is no
house bracket and no guys. It has been in place since 1970. Some of the
joints are a bit loose now, so I guess it is time to guy it. I am in central
Illinois. I am sure we have had winds over 50mph. Yes, I am amazed it is
still standing!
Milt, K9QZI
Wayne James
through my deck and was trapped by the 2X8 structure and decking around it. The first house bracket was screwed into
the 2nd floor header board. The next house bracket was under the eave, I put a 2X4 across the rafters under the facia,
I put the house bracket against that 2x4. Under the first 2X4 I put a short piece of 2x4 in between the house bracket and
screwed the two 2x4's together (this is what saved my tower...read on). I used the tower for years with no guy wires with
a TA-33A on it and a 4 element 2 meter beam on top. No guys. Now a few years later I put another section in ad the top was
about 65 feet, took the 2 meter beam off and put up a long Comet 2/440 fiberglass antenna on top. I decided to guy it this time.
Two guys over to the roof of my house with 6-2X8's stacked between the trusses with a large eyebolt throught them and a guy on a
12" tree in the back yard. Everything Worked fine for years and then "The F4 Tornado in Chattanooga of 2020" came through, the TA 33 antenna and the Comet ended up in my neighbors back yard! The tower was left standing and the Phillystrand 2400# guy broke, the one going to a tree in the back yard. The tree was missing too! I had eight 60 ft + trees fall missing our house with now damage to the house, all the trees in my yard were on the ground except one that was broken off. However the tower remaind standing but was leaning some I thought all the sections were bent. After taking down three sections we noticed they were all straignt and the 42 foot of tower still up just above the gutter appeared straight when we took the house brackets off. The brackets were bent sideways holding the tower over some. I found out that the tornado pressed so hard on the tower that it took the house bracket and bent the ends of the flat part of the bracket that attached to the tower. So the house bracket saved the tower but the bracket was bent. I put the house bracket side pieces in a press and straightened them out and attached new angle with holes in it down the side of each bracket for strength. The house brackets cannot take sideways motion of the tower as built. The real
saver was the two 2X4's I put across the rafters of the hang over and inbetween the house brackets. Incidently I picked up the Comet antenna thinking
it was a goner as was my TA-33 one element looked like a paper clip. Any how I took home the Comet and put it on a tripod on my deck and checked
in on the Oak Ridge Repeater with about 10 watts 100+ miles away, it survived!
Allodoxaphobia
reply to a 27 year old post.