Hello everybody and welcome back to Everything Hamradio! Today we are going to be talking about Towers! In amateur radio, or any type of radio communications for that matter, you are going to probably use some type of tower, whether it is a pole or a full blown tower. You might not use a tower, but more than likely, you eventually will if you have a home station. When I first got my license, my first antenna for a “home station” as a mag-mount antenna. My dad made me a piece of angle bracket that we screwed to the eve of my house and put the mag-mount on. It wasn’t the best antenna but it got me on the air. I later graduated to a 15′ pole, then a 20′ tower that he had built before I was born and now have a 65′ tower in my back yard.
There are several different type of pole classifications when it comes to towers. The first is just a standard section of pipe. When I first got into amateur radio, you could buy a 5′ section of pipe from Radio Shack that had a tapered end so you could combine two or more together to make it longer, but since Radio Shack isn’t what it use to be, I don’t know if they have it anymore. You can go down to your local hardware or home improvement store like Lowes or Home Depot and but like a 20′ section of 1″ galvanize steel pipe and use that. When I used a pole like this, I took a piece of rebar, about 2′ long and drove it in the ground until there was only about 6″ sticking up, placed the pole on top of it and attached it to the eve of my house with a C strap. The antenna was held on with a couple hose clamps at the top and it worked really well.
Another type of a pole “tower” is a push up pole. These can be a manual push up or an automatic one. Some clubs use these types of antennas for Field Day. You can actually buy one of these on a trailer from like an army surplus store even. I have seen some really neat setups that people have made that has a push up pole on a trailer. You have probably seen one of these types of poles that TV news vans. Whenever they get to a scene that they are covering, they can raise their transmitter up the length of the pole, which I have seen some that extend like 40-50 feet. How it stays connected to their TV station receiver is beyond me, cause I have seen them wiggle big time in the wind.
The picture on the right is of a Rohn H-40 Telescoping Push Up Pole. It has four sections of pipe that are about 8′ long each. This particular one can extend up to about 36′ and runs about $120. Each section has a locking screw that you tighten down once you extend that section.
A tower is a man made structure that is taller than it is wide, often by a large margin. Towers are among the highest structures in the world. There are approximately 50 towers that are taller than 600 meters or 1968.5 feet. The tallest radio tower was the Warsaw Radio Mast in Poland that measured a wopping 646.38 Meters or 2120.7 feet tall. It is the second tallest man made structure in the world, second only by the Burj Khalifa building that was completed in 2010. The tower collapsed in August of 1991.
Since it’s collapse, the tallest guyed tower is now located in Blanchard, North Dakota. It is the KVLY-TV mast and it stands a proud 628.8 meters or 2063 feet tall. Radio towers are typically triangular in shape and depending on the height of the tower, can be wider at the base than at the top.
In the picture on the right, even though there are cell phone towers, you can see two examples of a tower. The tower on the left, is a self supported tower. It doesn’t have any guy wires, therefore it is free standing. It takes up both more and less of a footprint than a guyed tower. More because the tower itself is wider than a guyed tower, but less because a guyed tower will have guy wires that extend out to normally 80% of its height.
I think I have only seen one of the “tripod” type towers used by a ham and that was because a cell phone provider wanted to use his property to put up a cell tower and one of the stipulations that he gave them was that he could put ham antennas on the top of it and they would install it for him and maintain the tower of course. I’d say it was a pretty good trade off, kind of wish I had a good place to put up a cell tower and my service was poor.
The other type of tower is a Tubular tower. These you often see as cell phone towers, electric transmission lines and wind turbines. They are basically just long tapered tubes and fairly large in diameter. I saw a video on youtube a while back showing a time lapse video of a wind turbine being erected. It was a pretty neat video and it really puts into perspective how big these towers can be and how heavy they are as well. In the video, the tower looked like it was like 20 feet across at about half way up and the two sections were held together by over 100 huge bolts. Then the turbine motor was placed on top, which they had to get this huge crane because it weighed something 100 tons.
Off the top of my head, I can think of two main types of tower bases. One is just a permanent installation, where the tower will stay in one spot as long as it remains erect. This type of base is uses on all of the larger towers. The second type of base is a tilt over base.
The anchor of the base should be between 20″ and 60″ deep depending on the height of the tower. Larger towers you should contact an engineer to get specs for the base and/or hire a professional tower erector. For the average amateur radio tower, 20-60″ should be more than sufficient. You should also make the hole about 20% wider than the width of the tower to give you room for the rebar and concrete.
With a tilt over tower, these are normally shorter towers and have a hinge built into the base and the entire tower will tilt over to allow you to work on your antennas without having to climb the tower. This is great especially for those of us who don’t particularly care for heights.
There are also towers that have a midpoint fold over. My dad’s, K5PWQ, tower has a break at about 7′ after he buried about 3′ of it in the ground. It has a crank on the base and allows the top two-thirds of the tower to fold over to where he can work on the antennas. By design or by accident, I don’t know which and he won’t admit to, when it folds over, he has to get up on the roof to work on it. Either way, it worked out pretty good, however, because this keeps the HF beam that he has on top of it off the ground and he can work on it at waste level instead of over his head.
How to Erect a Tower
After you have the base done and the cement is cured, the first leg is the easiest and it just gets harder from then, especially if you do not have a tilt over tower. You can use two different methods for erecting your tower. First you can rent a crane to lift the pieces into the air and onto the tower. This can be a little expensive if it takes a while to erect.
The cheaper way, and the method that is used in all taller tower erections, is to use what is called a Gin Pole. A gin pole is a pole that you attach at the top of your highest section of tower. On top of the gin pole is a pulley that allows you to pull the next section of the tower up to you. The gin pole will extend above the top a little more than the length of the section you are lifting and hold the next section in place while you lower it onto the already mounted tower pieces.
The picture to the right is a gin pole that was developed by WB0W. It is designed to clamp onto the rungs of a Rohn No. 25 and No. 45 tower.Click on the picture to be taken to his page to buy this an other items.
Lastly, lets touch a little bit on Guy wires. These are what keeps the tower stable. They should be made out of steel, to hold up to the wind load of your tower and antennas that is on it. I have 1/4″ steel cables that are on my tower. When you install them, they should be installed 120 degree apart from each other and the anchors should be at approximately 80% of the height of the tower away from the base. As far as installing your tower, follow the manufactures guidelines on where to attach then to the tower.
That about wraps up this entry. On my next post, we will be discussing feed lines and coaxes. If you haven’t done so already, please subscribe to my site to receive emails on when I publish a new article. Once you fill out the subscribe form, check your email. You will be getting an email from me with a link that you will need to click on in order to verify that it was you that subscribed; make sure and check your spam folder or Promotions tab on Gmail. Also, Like me on Facebook and follow me on Twitter, Google+ and LinkedIn. Links to all my social media pages can be found on the menu at the top of the page under Social.
Until next time…
73 de Curtis, K5CLM