By Joe Tischler- KN6JGX
No man is an island unto himself even during a pandemic. Thanks to seven men, including my three sons, and four weeks, my new hex beam antenna is in place and well established. I was originally going to fasten the mast to the chimney but that changed when my youngest son Adam suggested otherwise. When you consent to a little help you open the door to additional ideas, some good some not.
The initial purchase order was for the 5-band hex beam antenna, a mast, coaxial cable, thrust bearing and a rotor. You might rightly ask, “Joe why four weeks? This is not rocket science and you’re an electrical engineer!” A major influencing factor thrown into the mix was my roof, which had over seven leaks and needed complete replacement.
So, thinking ahead, we decided to put a hole in the eaves of the roof (there’s about a yard overhang from the exterior house wall to the edge of the roof, where the gutters are hung to the fascia boards.)
By doing this, the coax and rotor control cables could be routed through the roof instead of draping them over the gutter or running them along the surface of the roof. The initial 75-foot coax seemed to be more than enough, but once you loop the coax up and over and then through pipe, down and then back up again under the eaves, an extra ten feet of length was consumed. I had to order an additional 25’ of coax, not forgetting the proper PL-259-barrel connectors and the moisture sealant tape for the connections.
And what about a VHF/UHF antenna combination? After all, you do not want two holes in the roof. And what about the recommended feed-through coaxial choke? This antenna does not need a balun if you have a choke. We also needed a rotor controller and cable, an antenna analyzer and a signal strength meter. Just describing the items to order turns this short story into an epic saga. Keep in mind this is all being done during the pandemic, when we were not having any radio club meetings except for the on-line Zoom activities.
Seldom do things go as planned and this project was not an exception. I chose the hexagonal beam antenna because of its compact size and five-band HF coverage from 10 to 20 meters. There were several options including a two-band antenna and a fully DIY “buy everything yourself” option from purchased plans. I do like building things, but I chose to short-cut time and buy a more refined kit from DX Engineering.
The assembly of the antenna was spread out over three days, though it could have been done in a day. As seen in figure 1, the antenna looks like an inverted umbrella frame tensioned with Dacron line. The instructions detail the measurements that determine length of the fiberglass arms and the amount of bend. This is a dipole antenna and the director elements are fastened to the vertical arm attached to the mast at a logarithmic interval. The reflector wires are routed around the backside of the frame and attached via insulating Dacron cord to the director elements. All the wires come precut with crimped loop connectors on each end. Extra loops were provided in case trimming was necessary for final tuning, but I found that after raising the beast the SWRs were all less than 1.5:1 for each of the bands. Not bad considering measuring the SWRs on our outside teak table were over 5:1. I was prepared to nibble the ends of the directors to achieve good tuning but was relieved when it was unnecessary.
We went with a 2” diameter anchor pipe (Figure 2) that went through the roof with the proper flashing and shingles around it. Clamped to the anchor pipe were two mounting plates for the antenna rotor and the thrust bearing. One might ask, “why the thrust bearings? The medium duty antenna rotor should easily be able to carry the 25 lb. antenna.“ True, but move that 25 lbs. to the end of a 10 ft. mast and douse it with 40 to 60 mph winds and what do you have? Easily 200 pounds of torque swayed by the breeze. I can’t imagine a 200-pound person on top of that mast in 60 Mph winds, unless they were desperate to collect on a life insurance policy.
We did a fit check with the mast and the antenna and it didn’t fit…CRAP!! Adam inquired, “Dad, didn’t you check the antenna shaft with the mast?” The inside diameter of the mast was 1.25” and the mast was pretty close to that, but no joy. It was just as well because the mast was too flimsy. It was designed for a TV antenna rather than this HF heavyweight.
Where could we get a suitable mast? Home Depot does not have light 1½ inch pipe in 10-foot lengths. Besides, we would need something that would take the outside weather. One might be tempted to use the electrical steel conduit but beware, it’s like a soda can and will collapse with any force. Answer: Industrial Metal Supply company in San Fernando. They had chromium molybdenum (chrome-moly) steel pipe in 1 1/2“diameter size and I had a section cut to ten feet. This is the same steel use for bicycle frames and is corrosion resistant. Having a friend add the powder coating removed all weather corrosion concerns.
With Covid-19 reigning supreme I called in the order for the steel pipe and they had it ready for curb-side pickup in one hour. I did not have to go into the store and it just slid into my cavernous Chrysler Town & Country with no problem. You will note that we concocted a chimney brace, figure 3, and Adam strapped it to the top of the chimney, figure 4. I carry a torch and it comes in handy for welding such items on the fly.
Will is an electrical contractor, the man with the hammer drill in figure 5. He is seen here with an impact hammer driving the antenna grounding rod eight feet into the ground. One hole was not enough as there was a rock below. A second attempt was successful.
I had to stand back and let Adam finish off routing the cables along the side of the eaves and drilling holes in the stucco. He did not have a 2” carbide drill bit to penetrate the stucco so he made do with a ¼” bit and drilled half a dozen holes and knocked out the rest. His original idea was to run the cables down the inside of the wall, but oh no. Construction standards require horizontal fire breaks in the form of 2x4s. So, he raised the outlet opening. He cut neat rectangular holes by punching his keyhole saw through the drywall and then sawed the rest of the lines. No drilling was required. All was finally done including the cleanup of the dust and chips. It had been decades since the floor was swept in the computer room underneath and behind the transformed radio-shack desk. Now it’s Miller time!
Editor’s note: Joe recently passed his Technician and General exams and was granted his license and the calls KN6JGX on June 15, 2020. With his new hex beam antenna he’s all ready to enjoy Field Day!