A looming expiration date on my building permit finally motivated me to
schedule the tower raising party and get it done! Last Friday, 100' of Rohn
55 went up, along with two C31XR's and a 40-2CD, thanks to the help of a
crane. Using a crane was definitely the way to go! Many thanks to Gary
KK7DV, Chuck WA7JOS, Brett N7KG, and Debbie KD7GVF for the help on tower
raising day!
For those who would like pictures to go with the below narrative, check out:
http://www.pbase.com/tower1/tower1 and http://www.pbase.com/tower2/tower2
(pix courtesy of Gary KK7DV)
I had preassembled the first 90 feet with guy cables, coax, and rotor cables
over the last six months, so the day started with the first 90 feet of the
tower all ready to go. I had left the top 10 foot section (with it's mast,
rotor, and ring-rotor) separate because it has so much weight (the ring
rotor adds about 85 lbs or so).
The crane arrived, and we had a disagreement over where to set up the crane.
The operator wanted to set up on the highest ground near the tower (under
where a guy wire would go!) so he wouldn't need to extend the "jib" on the
crane. I wanted him to set up in the flat area right between two guys (but
a few feet below the base in elevation) so there would be more space for him
to swing the boom, but I lost the battle. In retrospect, I should have been
more forceful, but having not used a crane like this before, I deferred to
the operators experience. It turns out the operator had set free standing
cell towers before, but never a guyed tower!
We picked up the first 90 feet with the crane using three nylon slings
shackled to each of the legs right below a cross brace so that the tower
would hang evenly. As the crane lifted the tower, there was only a little
flexing in the tower at the very beginning. The flex was maybe 6" or so,
little enough I wouldn't hesitate to do it this way again. (If I had it to
do again, I would put the top section on also and lift it all in one piece.)
The crane then set the tower on the pin, and we pulled out the guy wires.
To keep the guy wires from tangling, I had pulled them along side the faces
of the tower and tied them to the tower in a few spots with string, coiled
the rest up at the bottom. This worked great, as each person just grabbed a
coil and started walking out, pulling the guy wire to easily break the
string. We used two transit levels to sight the vertical on the tower, and
used come-alongs to tension the guys to close to the right tension. Once
the lower guys were to the right tension and the tower plumb, we attached
the tail of the guys to the turnbuckle and took up the tension on the
turnbuckle. The process was repeated with the upper set of guys. The tails
of the guys were then looped through the turnbuckles and equalizer plates
and tied together with cable clamps to form a safety loop. I came back a
day later and rechecked the tension on all the guys when there was less
wind.
With the guys set, Gary (KK7DV) and I (N7VM) climbed up the 90 feet to await
the top section. After a miscue (the boom height wasn't quite enough the
way the section was first rigged) we placed the top section and, with a bit
of pushing, pulling, and hammering, were able to get the bolts through and
tightened. I far prefer the larger bolts on the Rohn 55 to Rohn 25 - the
Rohn 55 bolts can take a lot more abuse without getting stripped out: even
after hammering the bolts through, I was still able to put the nuts on by
hand!
At this point, the crane operator got his first look at the C31XR's we
planned to raise, and realized he was set up way to close to a guy wire to
lift them. While he moved the crane (to where I had originally suggested),
he fortunately "stopped" the clock and didn't charge for the time it took to
move the crane. He also extended the jib (which swings out and is pinned in
place) given him an extra 30 feet in height. Gary and I just hung out on the
tower while all this was done, which gave Gary an opportunity to take a
number of pictures.
With the crane reconfigured, we placed each of the antennas: the C31XR at
56' first, the second C31XR at 92', and then the 40-2CD at 107' (on a 12'
mast / 5' in the tower). By working bottom up, we didn't have to worry
about the lift cable hitting higher antennas. The C31XR's dropped into the
ring rotor cradles nicely, allowing us to disconnect the sling without even
having to bolt down the antenna first. The ground crew sent the C31XR's up
with the truss kits tied on with a rope so we had everything required to
bolt them down in one lift. While the crane was packing up, Gary and I
worked our way back down the tower, connecting and weatherproofing the coax
and rotor connections.
All in all, it took about 8 hours, about 5 of that with Gary and I on the
tower. A few things that could be done better next time: know exactly how
and where the crane is going to set up (cost almost an hour), allow lots of
margin on the height of the crane (cost us a half hour to re-rig), get the
guy wire lengths right (we had to move insulators on two upper guys that
were too long - costing another 1/2 an hour or more), and don't waste time
while the crane is there setting up antenna trusses (maybe another hour).
So, how do the antennas play? Well, I need to run about 300 feet of
underground cable to get the antennas connected to the house, so I've not
done much other than check the matches and work a couple of DX stations
field day style. Something is wrong with the upper tribander (funny how
it's never the lower antenna :-), since it is a terrible match on all bands.
It looks like a short at the bottom of the coax, but since the C31XR has a
DC shorted feedpoint, that's how it should look. The 40m beam is perfect
(SWR 1.7 at bottom end, 1.3 at 7.1 MHz, and 2.5 at the top) and the lower
tribander is pretty good - no worse than 2:1 anywhere on all three bands (I
might tweak 15m a little bit).
The first neighbor complaint was lodged right after the 40-2CD went on the
top. Since I was on the tower, my wife handled the complaint, and
apparently the neighbor was somewhat pacified by Deb's explanation of ham
radio, public service, and the fulfillment of a "life long dream." Next
complaint we'll also try to get "homeland security" in there somehow.
So, next, get the underground cables to the house in, fix the upper
tribander, and assemble the bulkheads and switching system. That's probably
not going to happen before CQ WPX...grumble...
73 de Bill N7VM
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