Albums: WA7DUH And WB7CNV Tower Construction
WA7DUH And WB7CNV Tower Construction
Photo essay of tower project at the station of Linda WB7CNV and Steve WA7DUH. They live just outside of the Richland and West Richland city limits in Benton County. Project is to initially erect a 65 ft guyed tower, but to design it for 75 ft or higher. Benton County has an ordinance controlling "communications facilities" (BCC 11.65) which includes "communication towers and antennas." Many of the requirements are exempted for amateur radio towers and antennas not exceeding 65 ft.P1010686 (Custom).JPG
Prior to tower project, 44 ft fiberglass poles hold up a G5RV non-resonant dipole at the WB7CNV/WA7DUH residence.
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Rebar grid construction for tower base.
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Diagonal rebar wires are used to keep the grid square.
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Linda WB7CNV cut about 450 tie wires for the tower base and 3 guy station rebar cages.
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Tower base hole as specificed will be 4ft x 4ft x 5ft deep. 1st 6 inches is gravel and sand for moisture drainage, followed by 4 cement blocks that hold the bottom rebar grid up into the poured concrete. Tower base legs stick down into the gravel/sand (below the concrete so as to drain any water that may form in the tower legs. Another rebar grid will be embedded in the poured concrete 42 inches above the bottom grid seen in the picture.
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The engineered specs call for #7 rebar (7/8"). Are we holding up a 2000 ft TV station antenna?
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Benton County exemption from Benton County Code (BCC) 11.65 Communications Facilities that is really aimed at commercial installations such as TV/Radio stations or cell towers. However, this exemption did not remove the requirement for a building permit, structural analysis and original drawings with original (not copy) signature/stamp of Wash. State licensed Professional Engineer. Tower manufacturer's analysis and drawings were not acceptable (not original or Wash. licensed).
Also, county building dept. wanted to impose most of the requirements of BCC 11.65 anyway "for your and neighbor's protection". We battled several issues.
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One of three rebar cages for guy stations. Each guy station consists of a reinforced block of concrete 6ft x 4ft x 2ft high buried 4 ft below grade. That long 3/4 in rod is what the guy lines are tied to, and is buried in the concrete block. Each rod will sustain at least 8000 lbs of pull, which is about 4X overkill, since the worst case forces with an 88 mph wind is calculated to be 1000 lbs. Building code in Benton Co. requires survival of 88 mph winds.
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The guy rods have 6 x 6 x 1/2 in steel plates to keep them from pulling out of the concrete guy station blocks. Picture shows drilling the 3/4 in holes for the rods. I need a slower turning drill press.
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Holes for guy station anchors are 6ft long,4 ft wide and 4 ft deep. Concrete blocks are used to hold the rebar cage up off the bottom 6 inches so they are embedded in concrete when poured. Painted lines indicate the level of concrete when poured.
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Lower painted line marks the height of the concrete.
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Yikes-- hit the sprinkler pipes. Anyone know a good way to find these sub-surface?
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The break wasn't so bad. The mess was created when the sprinkler controller decided to turn the water on, washed out the far bank and filled the hole. Duhhhh.
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Trying to fix a cave in. Sandy soil.
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Basic process when digging all the holes-- dirt goes in the cart, Linda (WB7CNV) hauls away.
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This cart has a dump function, which really helps unloading!
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It's 104 today, so sweat band and wet neck towell in use!
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Guy station base ready to be lowered into a guy station hole. Guy station blocks are buried about 4 feet down, so only half the dirt is hauled away. The pile in the background is what goes back in to cover it up.
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Originally tried to lift rebar cage from a single point, but it caused the rebar cage to deform. A lifting frame was then built which pulled up vertical instead of an angle.
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Rebar cage for guy station is lowered onto concrete blocks that elevate up off the bottom.
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The tower base hole. 2x4's above the forms hold up and align the top rebar grid. There is also lower grid sitting on concrete blocks. The tower base that will be submerged in concrete floats in the center of both the top and bottom rebar grids. Temporary guy ropes hold the tower in perfect plumb. Grandson Adam approves.
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A better view of the rebar cage.
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Adam loves Jessica Kabota.
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Time to pour concrete. The concrete truck can only reach one guy station, so a motorized wheel barrel is used to transport 8 yards of concrete into the main tower and guy station holes.
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Yea-- this is the way to handle concrete.
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Guys from Speedy Angeles Concrete, LLC out of Pasco WA do the work. They have the equipment and muscle, and did the job for a good price.
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WB7CNV (Linda) bows properly to the tower gods.
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Trenching between the tower base and the ham shack entrance. The picture doesn't really show the 18% downslope here, and the trencher was stuck and rolling into one of the deck support posts. Come-alongs are keeping the trencher from taking out the deck post plus the tractor is extracting.
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One of three ground tower ground rods. The are each connected to a tower leg with both a #4 solid copper wire (per NEC) PLUS a 1 1/2 inch low RF impedance copper strap. Once connections are made, the ground rod is then driven down so it is at least 6 inches below grade.
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The #4 solid wire and the copper strap is also run to the house electrical ground and into the ham shack entrance.
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Here is the house ground rod as we found it. It doesn't meet code. Only one ground was found or wired into the electrical panel, but code requires two, with at least 6ft separating them. The solid copper wire is also too small, and the one rod was not 6 inches below grade. So we fixed that up.
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#4 solid copper over to the house electrical entrance ground. Found more irrigation, Spinkler valve control cable (run in water pipe PVC) and some Romex (indoor only) that the previous owner had run to some outdoor lights. Gotta fix all that.
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Driving those ground rods down at least 6 inches below grade with a power hammer.
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Each of the 3 tower grounds are out abot 7 feet from each tower leg, with #4 solid copper and 1 1/2 inch copper strap back to the tower, over to the house electrical ground and down to the ham shack. Two inch rigid non-metal conduit is also buried in the trench to hold 4 runs of LMR-400 coax.
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A view of the trench heading down to the ham shack. That white bottle in the picture is copper anti-seize/anti-corrosion goop that is used liberally on ALL copper-to-copper connections.
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It looks like coax in this picture, but it is Phillystran, a non-conductive arimid fiber guy wire. Good for about 4,000 lbs pull.