Saturday, April 28, 2012

Adding the A743 to the A3S

Unfortunately, I don't have any pictures to share of this, but Jerry NG6R's question this week reminded me of the ordeal -- so I figured I should share it with everyone. 


I added the A743 to the A3S in September of 2005. The A3S had been up on the tower for four years at this point. I remember running into some difficulty with this update.

  1. Remove Rotator - rather straightforward. Loosen the rotator clamps and lever the mast up a centimeter or two before tightening down the clamping screws on the tower top. Remove the rotator clamps, screws, unhook the rotator cables (you did use a weatherproof connector for this, didn't you?), and pull the rotator out. I think I attached a sling to the rotator and hung it off the side of the tower using a carabiner for the duration.
  2. Lower Mast and Antenna to Top of Tower - this step always makes me nervous, as I always think the 70+ lbs  of mast, antenna and whatnot is going to come crashing down suddenly and impale a foot, hand or arm as I loosen clamping screws in the tower top.
  3. Remove Driven Element. First loosen the U-bolt and swing the element up vertically. I then attached a sling just above the boom and then removed the U-bolt. (This way, the element can't get away from me an go crashing to the ground) Then attach to a rope and lower to the ground.
  4. Update Driven Element with A743 Components. Be sure to follow the tips in my original article. I used the dimensions half-way between CW and MID in the manual. Double-check your dimensions. Take care to avoid bending the capacity hat. Go ahead and attach the driven element support rope clamps, and tie the rope to one clamp. You can't tie the other side, since it has to go over the boom.
  5. Mount the Driven Element. This bit was tricky. The element is much harder to haul up the tower, since you have to avoid snagging the capacity hats. Bring it up vertically and attach the U-bolt, but don't tighten it down just yet. Toss the support rope over the boom and swing the driven element up so you can climb down and tie off the support rope. (Don't forget to put the support rope through the grommet on the support mast) Rotate the driven element back down to horizontal. The Driven Element is strong enough to support itself, at least in the short term.
  6. Mount the Driven Element Support Mast. Hardest bit. The amount of slack in the rope depends on where you put the support rope clamps and how long the rope is. I barely had enough slack to get the bottom U-bolt on the support mast. Once that is done you need to adjust the height of the mast to get the Driven Element level with the other elements. This is a tough operation, since you are above the tower, and have to hold the mast up with one hand and tighten the clamp with the other. Don't forget the twist in the rope. Without it, you'll be back up the tower in a year or two to replace the rope.
  7. Raise Mast and Antenna. Again a nervous operation. If your mast is heavy, you should use a come-along. Mine isn't terribly, so I used a pulley arrangement. 
  8. Replace Rotator. Reverse of the previous steps. 

Sounds simple, doesn't it? No. Well, it took me about a half-dozen climbs to finish this off in the fall of 2005, and then I had to do it again when the support rope broken. I haven't had any trouble since then.

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