Rohn tower without guy lines?

[Lesley Bulluck]

Hello everyone,

I am planning to erect a Motus tower at the VCU Rice Rivers Center (university research station along James River, SE of Richmond, VA) and we are debating two potential install options. One is to an existing I-beam of a building and the other (preferred by administration) is an existing Rohn tower that houses a met station.  

Here is a picture of the existing tower:

This station has been in place since 2009 without guy lines.  It is attached to a 3x3x3 concrete base.  Would adding another 3m Rohn section along with two 9-element Yagi's and 3-4 6 element Yagi's require the addition of guy lines? 

I recently attended the Powdermill virtual workshop and did not see any examples of a non-guyed tower, so definitely wanted to check with you all before moving forward with this option. 

Thank you for any insight you might have.

Lesley Bulluck

VCU Center for Environmental Studies

[David F. Brinker]

Leslie,

You left out one important detail, how tall is the existing Rohn tower?  Free standing Rohn towers are possible up tp 40 ft. with adequate foundation.  I think that the specs recommended by Rohn for a 40 ft. freestanding tower require a larger foundation block than one cubic yard, but that is easy to look up.

David F. Brinker
1200 Frederick Rd.
Catonsville, Maryland 21228

Project SNOWstorm (www.ProjectSNOWstorm.org),
Northern Goshawk Demographics Project &
Project Owlnet (www.ProjectOwlnet.org)
Assateague Island Banding Station
38 09 53 N, 75 10 24 W

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[Lesley Bulluck]

Excellent! and good point. The tower is currently 25 feet, and we would like to make it taller...up to 40 feet if possible.

It is not clear if the whole tower will have to be replaced (b/c it is old and may not be compatible with newer Rohn pieces.

Thanks!

[Pat Lorch]

Hello Lesley,

    We did pretty much did exactly what you are asking here on an old Rohn tower that we estimated was 40’ or so tall. Our bucket truck could not reach much above 30’. It was our feeling that the tower could support these antennas, though we did debate it. A couple of badly perched turkey vultures on a windy day on the other hand… You have the advantage of it not being on an existing building, so less lightning protection will be needed.   Also if it does come down it will not hit a building. 

Patrick Lorch

plor...@gmail.com

On Mar 28, 2022, at 2:53 PM, Lesley Bulluck <lbul...@gmail.com> wrote:

Excellent! and good point. The tower is currently 25 feet, and we would like to make it taller...up to 40 feet if possible.

To view this discussion on the web visit https://groups.google.com/d/msgid/motus-wts/a67b2a35-2541-46ba-8c49-820fa633af16n%40googlegroups.com.

[Jim Moore]

Leslie-

It looks like Rohn 25-G tower and if you are planning to extend to 40' I would recommend guying the tower, especially if you are planning to climb it.  To get to 40 feet you will need to remove the top section with the tapered mast mount and add one or two 10' sections depending on your budget.  You will need a gin pole and tower jack to separate the top section.  I used a home brew gin pole which I loaned (donated) to Todd Alleger a few years back.  Maybe he could loan that to you if you are in the New England area.

Jim Moore

[Todd Alleger]

Lesley,

I think you have a good resource here, but looking closely, it seems like you have a three section tower, which tapers a bit as each section goes into the next.  That means it's not the easily purchased Rohn 25G, but something else, which could make sourcing and adding sections even trickier.  Maybe the folks who put it up are still around and would be able to tell you what type of tower it is or how to get extra sections?  On the plus side, it looks to be well grounded!

My suggestion would be to determine the the size mast that would fit into the top cap and buy a 10' galvanized steel or aluminum mast to fit.  This would get you a little more height (6-7ft or so) and put your 5 or 6 antennas above the existing equipment (or maybe that stuff can be removed?).  Using a lift would allow the work to be done without a climber and a 50' towable lift are easy to use and can be rented fairly cheaply.  A 100w solar paned can be mounted on the middle section (if you need power) and receiver, battery, & connections mounted in a box on the tower like in the photo.

 Todd