|On October 24, 2005,
hurricane Wilma paid us a visit. During the second half of the storm
the side angle brace of the antenna bracket (called a "stiff arm") broke
and allowed the entire bracket to be twisted. This tilted the antenna
toward the southeast (about 30 degrees from vertical to the east and over 45 degrees to
the south), with the dipole elements pointing up above the horizon to the northwest. The antenna was also bent slightly, but
still working OK (SWR 1.2:1). Because of the distorted radiation
pattern, distant and low power stations had difficulty accessing the repeater.
On December 14th a tower climbing crew from Kirms Communication straightened the bracket, replaced the stiff arm, and installed a new antenna. It turned out to be a challenging job and we were impressed by the professionalism and ingenuity of the Kirms crew. You will get to meet them in the photos below.
It was a fascinating procedure. Some Repeater Group Members were on site and we agreed that other hams might enjoy seeing how the work was done. The entire process was photographed and we have posted a selection here which shows the job at each stage. A brief narration is included with the photos. We hope you will enjoy the slide show and find it as interesting as we did.
AREC Board of Directors
8:45 am - The new antenna is ready to go. This is a good
shot to show how long the antenna is (23').
The climbing crew from Kirms arrives. That's our new
stiff arm on the rack.
Mike, crew foreman and climber, getting ready
Ready to go up. Notice the pulley and rope he will carry
with him. At the top
he will fasten the pulley to the tower and use it for hauling the heavy stuff
A beautiful morning. Cool, clear and still.
We have an observer (our "bird watt meter" - thanks Jamie)
Just past the first guy wires, about 75'
Approaching the main dish cluster, over 200'
At this point he has been climbing for 11 minutes.
Around 300'. At this point he has been climbing for 22
Our antenna with the broken stiff arm is visible at the upper left, just above
the two stick antennas. From this angle it's slight bend can be seen,
just above the first element..
Entering rarified atmosphere, over 300' (and 29 minutes). Our antenna,
just below the torque collar, is at 355'
"Houston, we have a problem." When Mike got to the
torque collar where he would be working,
he found a loose antenna that had broken completely off its mast. It was held only by an element hooked
over its support bracket and was flopping around in the wind (this antenna is visible in the picture taken
the day after the hurricane, at the bottom of the antenna photo page, and the element hooked over
the bracket is clearly visible). It would have to be removed before anything else could be done .
In this photo he has hooked the pulley to the tower above the bracket, tied the rope to the antenna,
and with ground crew controlling the tension has unhooked the antenna from the bracket.
Sending it down. Our antenna is
visible on the opposite side
below the collar. This angle shows how bad the tilt is.
We've been warming clouds with our signals.
Only 200' more to go.
The next step is to go up above our antenna and fasten the pully
where it will
be used for the rest of the job. Here, Mike has attached a weight and is
lowering it to the ground crew who will attach a cable from a winch
on the truck. It can then be used for ferrying heavier things.
This close up shot gives us a good look at our broken stiff
Does that buzzard have a hungry look in his eye?
The ground crew has attached the cable with another pulley and
is pulling it back up. The pulley
will be fastened to the tower and the cable end, with rope still attached, will make a round trip back to
the ground. The winch can then be used to raise the heavier materials. The rope will remain attached
to the cable and will act as a control line from the ground. Notice the canvas tool bag.
Up goes the tool bag. The point where the
rope and cable connect contains a central ring
to which various things can be fastened. This is the primary working point for the system.
It allows the ground crew to assist the climber in moving parts into position by
raising and lowering with the cable, and adjusting the position with the rope.
Mike is securing the tool bag. This angle gives us a
dramatic view of our antenna.
The next order of business is to remove the broken stiff arm.
Mike is tying a line to it in this shot.
Removing the stiff arm bolts...
The ground crew waits to lower the stiff arm. Ozzie on
the left, and Papa.
Here it comes...
Wow! What a mess. The rest of the support bracket is
in good condition.
The new antenna is in the background.
The next task is to straighten the offset bracket, and it
turned out to be the biggest
challenge of the day. Here, Mike is fastening one end of a come-along to the top
of the bracket. The other end will be on the north tower leg behind him.
Here he can be seen using the come-along ratchet to pull the
back into alignment. The old antenna is still attached because
it is too difficult to remove in this position.
The next task is to remove the old antenna. In this
shot Mike has used the
come-along again, this time to swing the entire bracket to the south (it normally
points southwest) in order to position the top of the antenna close to the antenna
bracket above it. This will allow him to walk out on that bracket and reach the
antenna tip to fasten the cable. In this shot the come-along can be seen
running from under his right foot over to the east tower leg.
Next, Mike is fastening the rope/cable connector to the base of the antenna.
In this shot he has walked out on the upper bracket and is
fastening the cable to
the top of the antenna. Then he will go back down and remove the antenna
from the bracket. This top attachment allows the ground crew to control
the tension and keep the antenna vertical when its clamps are loosened
Here, he has removed the antenna and signals the ground crew
to lower it.
Notice how a simple clip is used to fasten the cable to the
for the trip down.
On the ground, the new antenna get its clamps adjusted.
The old antenna is on the left.
From left to right: Papa and Ozzie from Kirms, and Rex KF4FAJ.
Up she goes. Looks like a rocket
Positioning the new antenna is a careful balancing act, with
the ground crew
controlling tension on the top with the cable. They are in contact
by radio as well as hand signals. He carries two radios, in case one fails.
Now he is heading back to the upper bracket. The cable
is still attached
to the top of the antenna.
Releasing the cable
At this point the bracket has been swung back to the
southwest, and Mike
is aligning the elements to the west (a final more precise alignment was done
at the end, with help from the ground crew on the radio).
Couldn't resist this shot
The next step is installing the new stiff arm. Here it
is en route via the
Installing the new stiff arm. The right end goes through
U-bolts on a plate
attached to the tower leg, which can be seen clearly in photo #31.
Notice that the left end is still attached to the cable/rope link,
controlled by the ground crew.
The stiff arm installation completed, Mike is now beginning
the final alignments,
which required some more pulling on the bracket, adjusting the stiff arm,
turning the antenna a few degrees, and, finally, adding an extra clamp plate
to the bottom antenna clamp in order to shim it out. This was necessary
because he could not get the bracket end perfectly vertical.
All done. SWR is 1.1:1 We're back in full coverage operation.
Our thanks to Kirms Communication for doing an excellent job under challenging circumstances.
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