A major part of my station is my 70 foot Rohn 45G guyed tower in my backyard. The tower was installation was finished in December of 2011 with a great amount of help from Doug (N7BFS) and Karl(AK2O). My Father, Paul and my Brother, Joe also helped with Ground crew work.
The tower base is built using a rebar structure in which a bottom section of Rohn 45 is tied to with tie wire. You can see that the tower bottom does not meet up with the bottom of the rebar. That is to give some room for more concrete below it to give it a better hold in the ground. Next we placed the section into the ground with a form around the rebar. Here you can see I drove rebar into the ground around the form to keep it together while the concrete was in it curing. There is then wire tied around each of the vertical rebar retainers to further hold this together. The bits of 2×4 are place to keep the tower vertical as we can while the concrete cures. the tower base is 3 cubic yards.
Guy Wire Anchors:
Each of the guy wire anchors are built using a rebar frame and a 5/8″ diameter J bolt. This has a “J” shape hook on one end and an eye hook on the other. The whole thing is then hot dipped galvanized to keep it from rusting. The base of the anchor made from a frame or rebar which the “J” is hooked to. The bolt then runs through a concrete tube, using rebar to keep it centered, and then the top is exposed. Each bolt is about 5 feet long.
A form was then built around the rebar and concrete tube to hold it all in place while the concrete cured. The base part of the unit provided the maximum resistance because it has a large surface area for the dit to hold it in place. The concrete around the bolt keeps it from coming in contact with the soil. This prevents galvanic corrosion from occurring by leaching ions from the zinc in the galvanizing to the copper in the grounding system. The final product looks something like this:
The tower has two sets of guy wires, one at the 50 foot level, and one just below the top. This makes sure that the tower will not twist under wind load. The brackets used are the Rohn factory brackets. The guy wires I used where 4.75mm(3/16″) aircraft cable. This cable is made of stainless steel so it will not rust over time and it is much more resistant to fatiguing over time. I then use the same of the same cable to run a messenger cable from the tower to my house where the cable enters the building and runs to the ham shack. Now I know a messenger cable is not the best way to do this. An ice bridge would have been better because it is ridged. I was unable to install an ice bridge because of cost and it would have made it hard for me to get my farm equipment around the tower. So I do the best I can with the cable.
Above is a picture of the antennas as I have them installed now.
The cross arms are build from an old open loop dipole antenna mounting mast(I think it was a DB-440 type antenna that was 40 feet tall). That makes up the horizontal parts. The Verticals are two 2″ scheduled 40 aluminum pipe. It’s mounted to the tower and held together by cross over plats.
The 40m Dipole is mounted on an old low band yagi boom. When I got the antenna the boom was bent due to Ice loading. It and the mount was quite heavy duty(The pipe was about 2mm thickness) and so I removed the elements and made an attachment point at the tip of it.
All the antennas have LDF4(1/2″ hard line) running to them. The dipole has a 3 foot jumper of RG-214 running to the balen so it has some flexibility for movement in the wind.
Bad cable management is one of my pet peevs at radio sites. Poor cable management causes all kind of issue when working on a tower and trying to troubleshoot and system. So I made sure to keep things clean at my personal site.
Grounding is VERY IMPORTANT! I know this is a debated subject among many Ham radio operators because of the myth that grounding attracts lighting to your site.
*Motorola R56-2005: This link will bring you to an old copy of the R56 Site standards. Go to section 4.2 and read up on Lighting. R56 covers in great detail on what happens with lighting and how it effects your radio site.*
This myth has been proven wrong, lighting goes where ever the impedance is lowest, and that can be anywhere due to the moving nature of cloud/ground charge. So the best bet is to Protect things as much as you can.
But you may ask, how does grounding protect your site?
By preventing potential difference between your equipment and the ground.
Just before lighting strikes, the potential(Voltage) of the ground rises from it’s normal resting state. If your equipment does not have a good connection to the ground voltage can develop between the ground and your equipment. Right before the strike happens this voltage can reach Megavolts! That will kill just about anything!
So to prevent this we make sure to have a good connection between our equipment and the ground.
Tower grounding is where it all starts, as it is the tallest part of the system. Remember that each part of the system needs to be grounded, The tower, guy wires, cables, etc.
Each element of the grounding system also needs to be connected as well. This is so when the ground voltage rises, all the elements of your system rise with the ground in the same amount. The goal here is to prevent potential difference.
I have not gotten as far as I would like on grounding my system at this point. but I’m am slowly getting there.