August 15, 2007
50Mhz. 235’ rotating tower array at K3TKJ
– W3DOG VHF contest station in
In 1986 I bought my first big tower, big to me at least, 100’ of Rohn 45. With the help of friends and an antenna party I got it and some HF antennas up and working. As I would look at that tower I had a dream of making the entire tower rotate. I did not know how to do that nor had I ever heard of one. Around 1989 I installed the second 100’ Rohn 45 tower, but in the back of my mind the possibility of a rotating tower was always there.
This is how this project was born.
So now it’s 2007 and others with my dream have built rotating towers and there are companies where the technology and hardware is available. After dreaming, scheming and talking about a big rotating tower for years I knew it had to be done. I gently floated the idea by my wife and best friend Denise and she was not opposed to me giving it a go. I now started in earnest assembling the remaining components needed.
The two original 100’ Rohn 45 towers were now down and
stored since my relocation to
My property is large but for the last 10 years all but 2 acres has been farmed by the adjacent land owner. My first task was to tell my neighbor that a tower was coming and I needed my land back. After numerous starts and stops the stake pounding was over and I had determined the location for the tower and the guy points. This was calculated to require 1.7 acres. I took that amount but actually the tower is not so intrusive that the rest of the property cannot be used for other things. (I think there is a fruit tree orchard and some grape arbors in my future.)
The great thing about ham radio as a hobby is the support
from friend and strangers alike. When I announced what I was going to attempt
many offered help and suggestions. My good friend Ray KA3EKH located a set of
guy anchors made by Rohn for a 500’ tower. Weighing in at 700 pounds each these were quickly incorporated in the plan with the
specified Rohn anchors looking so inadequate by comparison. Bob W9GE just
happen to have a new K0XG rotating base and one guy ring that he was not going
to use, a quick deal was made and I was on my way. I first met Richard K0XG in the flea market
at the Dayton Hamvention. He was displaying his rotating hardware and we talked
in great length about the how-to’s and the why-to of rotating a tower. This scene
repeated itself for the next 3 years. I went, we talked, and I came home with
all his literature and dreamed for another year. When I called Richard 2 months
before Dayton 2007 and placed an order I am sure he was relieved to finally see
me stop talking and start acting. Richard promised delivery at
After
Formula to calculate clearance for rotating antennas under guy wires:
tr = g(h-a)
------
h
where:
tr = allowable turning radius
g = distance from the tower base to the anchor of the guy
wire you are trying to clear.
h = height on the tower where the guy wire you are trying to
clear attaches.
a = antenna height
example:
100 foot tower, two sets of guy wires anchored 80' from base.
You are trying to clear the top guy, which is at the 100' level,
for an antenna at 51 foot height.
tr = 80 (100 - 51)
-------------
100
tr = 39.2' allowable turning radius
My final configuration was single guy points 160’ from the tower base. And guy ring bearings at 56’ 110’ 164’ and 218’. This, along with the antenna heights above gave me around 41’ clearance from the guy wires.
In every project there comes a time to shoot the Engineer and just build it. I hit that time and in early June I rented a backhoe and with the help of Bob WA3GGM the base and anchor holes were dug and the anchors were set in place and aligned. The holes were 5’ x5’ x5’ and it was calculated to need 10 yards of concrete for the 4 holes. I dug the holes on Friday and on Monday morning I poured the concrete with the help of my Father-in-Law, Charles “Lefty” Wright.
It was decided that the best way to install the tower was by crane and 50-60’ sections would be built as it would cause no strain on the tower to lift it that length. The rest of June and most of July was spent assembling the sections and adding the rotating guy rings as well as the brackets to hold the antenna booms on place. The antennas have overhead support lines and the brackets for that were put in place as well. Many evenings were devoted to this with frequent trips to the hardware store for more bolts, u-bolts and associated hardware. I was shocked by the shear amount of hardware it takes to assemble all this. It was amusing to see all the borrowed saw horses under the tower I think it took about 14 sets and I begged them from friends and relatives. My final act was to spray anything that looked like it might rust with “cold galvanizing” This is a zinc based paint that can be bought at hardware and home supply stores. It is recommended.
With the concrete and tower ready, I called the local crane company and contracted for a crane with a “ hook height” of 235’. This is a big crane and it comes with a big cost. The permits for it to travel on the highway were several hundred dollars. And the final agreed upon price to set the tower was over $3000. That is a lot of money but it is fast and it is safe to do it that way and safe was what I wanted most. Ironically the crane company is owned by a ham, but when a crane costs a million dollars, I guess there can be no discounts.
The climbing, section bolting, guy preparation, tensioning and making the tower plumb was contracted to a local tower company.
Everything was in place, and August 8, 2007 was the day. I watched the weather for thunderstorms and wind, the day was forecast to be perfect with one small exception it was going to be the hottest day in recent years. I bought 4 cases of water and some beer for the after tower celebration. I was nervous and I admit I did not sleep very well waiting for the big day. Several friends planned to be there to watch and help.
The day arrived and the crane and tower crew were on site at 7AM, it was already in the high 80’s and the humidity was about 90%. Soon after N3SVB, NE3Y, WA3GGM, N3DB, N3NO, and W3DR arrived to help. Other than helping put the guy wire in position and carrying water we mostly stayed out of the way and let the professionals do what they do best. At 2PM the tower was topped out, tensioned and plumb. We drank 96 bottles of water! No one ever drank any beer it was just to hot for that even. After a quick pickup of tools I invited the tower crew and all my helpers to the local pizza place for lunch. I took a slow drive back home very happy with myself and the days events, just as I rounded the corner about ½ mile from home I saw it from a distance the first time. I remember exclaiming “holy shit”. It was impressive standing there, even without antennas. My other towers look small by comparison now.
The next phase of the project has now begun. Trenching feed line and control cables to the tower. Building power dividers and phasing lines for 8 antennas. After I make some more progress I will continue with the story.
73, Al K3TKJ