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««« permit & foundation «« tower install « antenna install
Fall 2011: antennas, rotator, cables & lightning protection
The OptiBeam OB6-3M tribander is a Yagi on 10 and 15 meters but it's a Moxon on 20, making it possible for me to raise a beam with full-size elements in limited space. I find the look very clean and modern too. See my OB6-3M review on eHam.net. 
You might not notice the Diamond D220 2m-23cm mobile discone at the top if it weren't for the PVC pipe I used to mount it. Height matters: for local FM and D-STAR, even a J-pole would work great up there at 40+ feet! Here's my D220 review on eHam.net.
Below is a picture of both antennas riding the MA-40 tower up to full extension, as seen from the street:
The tower is easily turned by a medium-duty Yaesu G-800SA rotator, which is connected to the in-shack controller via landscaping wire that runs underground through a PVC conduit. The coax cables are taped together as they come down the side of the tower through two standoffs. Those cables then loop around the base to allow for turning the tower, and disappear into a second underground PVC conduit. To avoid tight bends in the coax, I used a weatherhead cover on that pipe.
(I later treated those rusty bolts in the base with Rustoleum and paint, and packed some concrete into the gap between the base and the foundation pad. I'll try to get a photo of that too.)
The cables come out of a weatherhead on the other end too, and then connect to Polyphaser lightning arrestors enclosed in a weatherproof utility box. I hope to add pictures of my own, but meanwhile I borrowed this shot. Clicking on it will take you to the DX Engineering grounding systems page.
My radios are also grounded to that box via a common point on my tuner. The box is connected to an 8' buried ground rod, which is in turn is connected to all other grounding points around the house, including the tower.
As you may recall from the foundation installation page, the tower base bolts are grounded inside the concrete to the foundation rebar and to another ground rod. All ground rods around the house are connected to each other by buried #10 wire, which terminates in a Ufer connection to the house foundation rebar. If you don't know anything about this - and even if your electrician says he does - it's worth investing in a copy of the National Fire Protection Association (NFPA) recommendations on lightning protection. They sell a protected PDF of that online.
All cables enter the house through a couple of 4" wide 3M Fire Barrier Pass-Through Devices, a neat little invention my electrician found at his electrical suppliers. I later stuffed insulation inside.
I hope this has been useful information for anyone considering one of these towers! See also my eHam review of the MA-40
««« permit & foundation «« tower install « antenna install
Other projects:
Antenna Farm 3: The Slanted Roof Solution
...and:
Antenna Farm 2: The Flat Roof Challenge
Flagpole Antenna Project • Antenna Farm 1
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