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Tower Construction

Several years ago, I installed a radio antenna mast at a former home. I had posted the process up on this site, but later took the site down after we moved. What follows are some photos descriptions and lessons learned of Tower #1. 

I picked up some used Rohn 25 tower sections from a local ham, the tower was older, and some sections were pretty beat up, but I was able to piece enough together to get the height I was looking for.  The tower came with quite a bit of guying hardware.  In the end, I had extra sections, parts and pieces.

The hole I dug held all of one cubic yard of concrete that I had delivered from a local redi-mix plant.  I filled the bottom with rock and installed a rebar cage, being careful not to allow any of the cage to be outside of the concrete that would be poured.  I used a short piece of tower section to bury in the concrete.  The stub was half in concrete and half out.  Later on, I would reconsider this method.  I felt the metal antenna tubing was vulnerable at the interface with the concrete.  Stress from torsion coupled with an elevated risk of oxidation or rusting by contact with water or soil made me think, I should have installed studs.  Metal studs would have been sturdier, and longer lasting than the relatively thin antenna tubing.

I had a torpedo top section but felt I needed a "flat top", so I picked up a thrust bearing plate for the 25G along with a Yeasu thrust bearing.  The thrust bearing plate was a Nello 25N.  This combination worked well atop the 30' tower and I had no issues with the Nello piece.

Approximately 1 cubic yard of concrete was used in the 3 foot by 3 foot by 3 foot hole.  The tower was held plub by 2x4 stakes and braces and the concrete cured.

Final touches on the concrete slab.  It is certain that this chunk of concrete will be in the ground for a long time.

I picked up a 24 foot lenght of 2 inch O.D. aluminum tubing with 0.25 inch wall for the mast.  I had to cut 4 foot off of this mast to get it down in the tower with my gin pole.  The gin pole is tall enough to set a 10' section of tower.  In order to balance the mast while hoisting it has to be secured about mid point.  That leaves about 2 foot extra on the bottom.  Trying to manhandle 24 foot of heavy duty aluminum tubing above my head turned out to be ... lets just say, unsafe, so I choped it down to a manageable size.

After it was completed, I had installed a Hy-Gain TH-3JR (Thunderbird JR) triband Yagi, a Cushcraft A50-3S 6 meter yagi, and a Hustler G6-144B VHF collinear vertical.  A Yeasu G-800DXA rotor was mounted about 10' from the top plate which turned the array.  I mounted a dipole hanger on the side of the antenna to support an 80 meter dipole.  Lengths of LMR 400 coax ran from the antenna down to the base of the antenna.

Lessons Learned:

  • On the next go round, I will likely pick up new sections of Rohn 25 or equivalent tower. 
  • I plan to cement in "J bolts" and use a mounting plate versus burying the short section of tower in the concrete.
  • The free standing tower at about 30 feet was plenty for the station at that location and the antenna selection was perfect.  I do not believe I will be needing that extra guying hardware.
  • LMR400 is not easy to solder PL-259 connectors to!

The final lesson learned is simply this. 

Build it. 

I planned a tower that would last a lifetime and it stayed up for 4 years.  Life has a way of changing your plans.