Rohn HBX-48 Install at N2VR
The challenge: Replace the fair-performing shed-top 8-foot tower with something around 50 feet. Given the ridge that runs along behind the property that seemed as high as we could go and still get signals from Europe down through Africa. The antenna from the shed tower -- Cushcraft A4S triband yagi -- would go up on the new tower. The shed tower was installed in August 1999 so was only 1 year old.
Many, many thanks to K2ZRB (left) and W2AD for a hard, hot day's work helping put the tower up section by section, and to neighbor Greg for a very critical half-hour assistance. Nothing could happen without friendly help!!!
Decision points: Didn't want guys -- too many deer in the back yard tripping over, and nibbling on, everything! And too many obstacles to mowing already. So freestanding it was, even with the reduced wind load compared to Rohn 25G. Cost looked about the same once you add in the guys and hardware required by the 25G. Labor was much more -- hand-digging in our rock and clay soil is accomplished with pick and shovel! Rohn specifies 4.1 cubic yards of concrete to anchor the HBX-48. 16 hours of soil moving later we ended up with a 4.6 cu yard foundation with a calculated weight of 18,050 lbs. This tower isn't going anywhere anytime soon.
- 2nd round of concrete poured, waiting to dry. You can see the shed-top tower that is being replaced in the upper right. The initial concrete pour wasn't enough to still thoughts of falling towers, so another hole was dug and filled to increase the size (and weight) of the concrete base.
- Second section of HBX installed. You can see the rather clumsy gin pole arrangement we used to hoist each section above the last. At 16 feet this is almost as high as the previous mounting point for the antenna!
- W2AD and N2VR down low. K2ZRB is apparently behind the camera. Fourth section about to come up.
- Let's skip a bunch of just plain hard work here and get to the good stuff!
- Last section going up. Here you can see the modus operandi in action. W2AD is on the ground pulling, N2VR strapped to the top, the last section being hoisted up. The extra wire in the left is one leg of an 80 meter antenna.
- Fitting the last section. Of course, manufacturing tolerances mean everything doesn't quite just slip into place. Some pushing and pulling is required to get the legs of the higher section to slide into the top of the lower section. In this case it wasn't too bad, thankfully!
- A very happy N2VR! This pic shows the difference in height between the shed tower and the HBX. N2VR is 5'10" tall so you can measure for yourself. The old antenna mount was about halfway up the mast in the shed tower. You can see some of the A4S as it leans against the far side of the shed.
- Getting ready to raise the A4S. There are some interesting problems when towers go right next to buildings, like a 32 foot wide antenna only 8 feet from a shed!
- Unfortunately we didn't get any other pics of dragging the A4S up the tower. Maybe next time. Neighbor Greg showed up just in time!
- The A4S at the top. Showing some of the lifting ropes.
- Looking straight up the side of the tower. On the right side you can see the stepping-in of the sides of the HBX. Nice design, pretty stable at the top in reasonable winds. Not as "movey" as I thought it might be.
- KC2EEU looking up. My favorite tower pics are those from the tops of the towers. This is looking down from 48 feet. The ground does slope up along the tower side of the shed, which explains the not-flat perception.
- Antenna inspection. D. Bill Platypus, Ferrari and shrimp fan extraordinaire, inspects the mounting, balun and feed point of the A4S.
- The view. This is looking west toward eastern Australia, through the trees and over the valley. We are in a glacier-cut valley running along 330 degrees magnetic. (Wasn't a ham when we bought the property.) The ridge to the west in this pic isn't much of a bother, but the one behind this camera shot gives some fits propagation-wise toward Africa.
For those with time and bandwidth to burn, here are all the pics from the project. Enjoy!
The tower really made this antenna come alive. Nothing like some proper height! In theory a 48 foot tower is just right for 15 meters, perhaps a tad high for optimal 10 meter work and not quite high enough for good 20m DX'ing. In reality it's a heck of a lot better than 18 feet off the ground and even helps getting over the nearby ridge on 20m. Signals from the north and west (Japan, China, Mongolia) are about 1 full S-unit louder, and a lot of signals that used to be buried in the noise are now readable. I love it when a project works out! If you have limited space and want a tower, definately look into the Rohn HBX option.
The shed tower was moved to the roof of the house for 6m/10m/VHF/UHF use. Stay tuned as antennas start springing up there.
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