Rohn 20 help

[jhusmc73]

I need to put up a tower about 40' high in a field to get wifi signal for Internet connectivity. I have 50 feet of Rohn 20 that was basically given to me. The base is on a hinged plate. I can't find anything for official specs for the 20, I assume because it's such a lightweight tower not intended for freestanding.

So, questions:

1. Can I install this with the hinged base bolted to studs in concrete then walk it up with 4 sections (including the base)? Not really excited about the idea of trying to climb this thing . How much concrete should I pour if this is the case?
2. Can I do this freestanding? Or, will I need to guy it?
3. If I need to guy it, does anyone have specs on the height(s) to guy it, and the distance from tower base and length of the guy wires?
4. Specs on the size of the guys?
5. What if I just did 30' (3 sections) instead of 40? Would that change anything?

I know I'm probably going to be told to invest in at least Rohn 25 instead, but would like to make use of these Rohn 20 sections if I can. The only thing that will be on the tower will be the 3.65Ghz Wireless radio that I'm guessing weighs 10 pounds max and is about 12"x18"x6" or so.

Or even better, if someone has a spec / install sheet they can guide me to for Rohn 20 them I'll work it out myself.

I appreciate the help in advance!

 

[Enforcer52]

Here is install specs for a 25 model, I wouldn't go any less for a 20.

Google is your friend.

https://www.3starinc.com/manuals/ROHN_G-SERIES_SELF_SUPPORT.pdf

 

[buddrousa]

Rohn 25G requires the base in a cubic foot of concrete 3 foot x 3 foot x 3 foot and a brace 30 feet above the ground (House Bracket or Guy Wires) every 30 feet. I have stood several 180 foot Rohn 25G's with 6 Guy Points 30 60 90 120 150 180. Put them up 1985 still standing today.
Never worked with Rohn 20 but if I did hinge it I would bot put much antenna load on it.

 

[jhusmc73]

Here is install specs for a 25 model, I wouldn't go any less for a 20.

Google is your friend.

https://www.3starinc.com/manuals/ROHN_G-SERIES_SELF_SUPPORT.pdf

Thank you. I had found that reference already, but it's for 25 and higher. Couldn't find anything on 20, and knowing that 20 is weaker than 25, I just needed to understand what I can / can't do with it.

Really appreciate the response and the guide though. This may be the best I get. Been searching and searching and have come up empty with specs on the 20.

I think I'm going to do 4 sections plus the top section and guy it at 30 feet since it's in a field and not next to my house. I'll do the 25 specs of 3x3x3 for concrete. My only debate at this point is whether to put the base in concrete, or to bury threaded studs and use the hinged base. Any feedback on this is appreciated as well.

Thanks again to you both for the feedback! I have had much help over the years from those in the HAM / tower industry, so I have much respect for all that is involved.

 

[mmckenna]

My only debate at this point is whether to put the base in concrete, or to bury threaded studs and use the hinged base. Any feedback on this is appreciated as well.

Look at the engineering drawings for the Rohn 25. You don't want to bury a section unless you provide proper drainage for water to exit the section under the concrete. Failure to do this will result in condensation gathering in the legs and eventually rusting out the base from the inside.

The threaded studs connected to the rebar are the way to go.

 

[Golay]

I gotta say this and I'll probably get flamed.
If all you're doing is putting a Wifi booster antenna on it, you're basically going to have a no load naked tower. Don't sue me for suggesting this. But if it was me, I'd just put it up freestanding. If l understood that it's just holding a WIFI antenna.

 

[buddrousa]

And you would watch it sway back and forth and fall when the holes got elongated.
Let me ask you how many 50 foot Rohn 25 Towers have you ever stood and climbed.

 

[mmckenna]

If l understood that it's just holding a WIFI antenna.

From his description, I think 'wifi' is being a bit loose. Sounds more like a point to point link. He mentions 10 pounds, 12" x 18" x 6".
Depending on the type, a swaying tower might result in the link dropping.

 

[merlin]

My Rhon tower was 40 foot, guyed at the top 4 way. The base plate on a yard concrete (3X3X3) rebar reinforced pad with J bolts.
A copper ground rod 6 foot into ground next to the pad with ground strap. I clocked the base plate to fold down into my yard.
Difference is mine supported a long boom 5 element Yagi on 10-foot pole down to a ham M rotator, so actual height was 48 foot.
The '71 Sylmar earthquake while I was away, I expected to find my tower down and twisted but survived.
Funny, I was at Magic Mountain 5 miles from Sylmar having breakfast when it hit. My house 30 miles south, made a mess of things.
Now If you are going up 40 foot, even with little wind load, you really should guy the tower. 30 foot should free stand, no problem.
Rhon tower are more rugged than you think, even with the one bolt at the base.

then walk it up with 4 sections

I had to rig a pulley at the house and used 10 MM climbing rope attached to a yard tractor to raise mine.
Erecting, it was free standing at 30 foot with me and a J-pole hoist to get the top section mounted. Swayed a little but handled it.
I would never bury a section into concrete, that hinged base plate is stronger and has weep holes.

 

[merlin]

condensation gathering in the legs and eventually rusting out

It will still accumulate water below the weep holes.

 

[mmckenna]

It will still accumulate water below the weep holes.

Often the installation instructions have the base extending down into drain rock so there's a path for water to exit.