The big work for this summer is the installation of an M-Square 40M4LLDD. This is a 4 element linear loaded design with dual driven elements. It has a 42’ boom and the longest element is 50’ tip to tip. It weighs in at about 150#. See my tech note on balancing big antennas for some pictures of it on the ground under construction.
This is the rigging getting ready to lift. Note that I used a large rope tied to 2 places about 6’ apart on the boom to spread the lifting force a bit. This also keeps the rope clear of the boom-mast plate which makes putting U-bolts in a bit easier. The ropes are attached to the boom in a way that will force the elements to tilt upward toward the tower when the antenna is lifted to make it easier to get over guy wires. The view toward the tower shows the two tag lines, notice that they are tied with large bowline knots so that the knot can be untied and the rope removed from the boom while up the tower easily. What can’t be seen from this is that the antenna is backwards. The reflector is on the left in the picture, but when it is up on the tower the reflector has to be to the right. This is because I want to put the antenna on the far leg of the tower pointing the opposite direction toward Europe. You also can’t really see that the tram cable goes up to the guy bracket at 140’, but the antenna is destined for just above the 105’ guy bracket.
There weren’t enough people when we did the liftoff to get some pictures. Basically I first untied the temporary rope that was keeping the lifting line from pulling the antenna off the tripods while someone held it back. Then I increased tension on the tram line which actually lifted the antenna off the tripods so we could check the balance before sending it up. The balance was good so the Jeep in 4wd-low backed up from the tower to pull it up. Once it was above the 105’ guy bracket the tram wire was loosened so the antenna swung in toward the tower and came to rest on the guy wires just below the bracket. Here is the tag line crew hard at work.
Once I was up the tower the Jeep pulled the antenna up to its final height. I then swung the antenna around the tower. Now its pointing the right direction and the boom-mast plate is on the right leg of the tower so I put in the U-bolts. After the U-bolts were in it was time to remove the tram line and tag lines. Then it is time to install the boom brace. I connected the coax and came down to release the supervisor and pose with the ground crew minus one(pictured are n1sr, me, w3sm, kb2wjy, missing is w1to).
