The first part of our EME project is to put up a new tower to support our antennas. Our plans call for a 26′ tower built using three Rohn 55G tower sections. Four feet of the first section of the tower is cemented in a concrete footing to anchor the tower’s base. The tower is also going to be guyed to ensure that it is very stable.
We are working with Matt Strelow, KC1XX, and Andrew Toth of XX Towers to put up our new tower. Matt brought out his tractor and dug the footings for our tower and for the associated conduits that will carry coax and control cables to our shack. The photo above shows the completed hole and form for the main tower base. Matt is working on the footings for one of the three guy anchors.
Here’s a closer look at the tower base. The footing includes a rebar cage to reinforce the concrete footing. There is also 6″ of crushed stone in the bottom of the hole that the tower legs sit it. It is very important that the bottoms of the tower legs remain open and do not become plugged with cement so that water in the legs can drain. If the legs cannot drain properly, water will accumulate and freeze. This can split open the tower legs and ruin the tower.
We also installed two conduits (a 4″ and a 2″ run of schedule 80 conduits) from the base of our tower to our shack. These conduits will carry coax feed lines and control cables to our new tower. We used a pair of 22° elbows to create a smooth transition to bring the conduits out of the ground. This will ensure that our hardline and other coax cables can be placed in the conduits without creating excessive bends.
Conduits will fill with water even if they are sealed. This happens as a result of the condensation of water in the air. To prevent our conduits from filling with water, we created two drain pits at the bottom of the trench at the two lowest spots in the conduit runs and filled them with stone. We drilled a few holes in the bottom of the conduits above the drain pits to allow the water to drain so our cables will remain dry.
We also created a bonding ground cable run from our new tower to the ground system at our shack entry. The bonding system was created by driving an 8′ ground rod every 10′ in the trench between our new tower and the perimeter ground around our house.
#2 stranded copper ground cable was Cadweld’ed to each ground rod to create a ground path to bond the tower to the perimeter grounding system around our house. Using a Cadweld system is simple and produces strong connections that will not deteriorate.
Here’s a video that shows our a Cadweld is made. We’ll cover completing the ground connections to the tower and the perimeter grounding system in a future article.
Finally, we used some sections of rebar to firmly support the guy anchor rods prior to pouring the cement. If you look closely, you can see a portion of the rebar material in one of the guy anchor footings in the photo above.
The next step in this part of our project was to pour the cement. A large cement mixer brought the proper cement mix to our QTH and Matt used his tractor to transport the cement from the mixer to the forms. We did a bit of finishing work on the cement base for our tower and let the cement dry for a few days.
The last step was to remove the forms and backfill the footings. A little work with a cement finishing block was done on the cement base to round off the rough edges left by the forms. The cable conduits emerge from the ground next to the tower base. You can also see one end of the copper bonding cable next to the conduits as well.
Here’s one of the completed guy anchor rods after backfilling. We are going to let the cement harden for a couple of weeks and then we’ll complete the construction of our new tower.
Here are some links to other articles in our series about our EME Station 2.0 project:
- EME Station 2.0 Part 1 – Goals and Station Design
- EME Station 2.0 Part 3 – Phase Tuned Receive Coax Cables
- EME Station 2.0 Part 4 – New EME Tower Is Up!
- EME Station 2.0 Part 5 – Control Cables and Rotator Controller
- EME Station 2.0 Part 6 – Tower Grounding System
- EME Station 2.0 Part 7 – Building Antennas
- EME Station 2.0 Part 8 – Elevation Rotator Assembly and Sub-System Test
- EME Station 2.0 Part 9 – H-Frame Assembly
- EME Station 2.0 Part 10 – Antennas On The Tower
- EME Station 2.0 Part 11 – Station Hardware in the Shack
- EME Station 2.0 Part 12 – Station Software
- EME Station 2.0 Part 13 – H-Frame Enhancements
If you’d like to learn more about How To Get Started in EME, check out the Nashua Area Radio Society Teach Night on this topic. You can find the EME Tech Night here.
Well I’m trying to find how to build the form for the base concrete and hold the antenna base leavel for the concrete pour
You can check Rohn’s website for the specifications (size and reinforcing) for tower bases. If you are not familiar with concrete forming and related work, you might want to work with a concrete foundation pro on your first project to see how to approach the forming and concrete work properly.