Excuse the bandwidth on this, but I thought it might be interesting to
some (many?) on the reflector.
Tower work and observations
This morning, a half-dozen members of the JSC ARC met at the
club station (W5RRR) to do some work. I climbed the 80' tower
which supports a 4el 15m beam at 90' and a 204BA at 80'. The
rotor has been giving us flukey meter readings, so the intent was
to remove the rotor and check it out on the ground. A second
purpose was to try to realign the director element of the 15m
beam. Either a heavy wind or a heavy bird caused the director to
rotate about 45 degrees. It had been this way for over a year or
two now and I was determined to fix it.
It seemed being the easiest of the tasks to perform up there, so
I undertook to realign the element first. I tied a 3/4" socket to
50lb test fishing line. I made a couple of test throws away from
the antenna elements and found that if I held the spool right, the
line would just spin off with little or no resistance. I then threw
the socket over the 15m beam director element such that the
string would land out on the element segment beyond the first
hose clamp, giving the leverage needed to move the element back
into place. It worked; the socket carried the line over and, still
holding the spool with the line looping off, it went right to the
ground. When one of the groundcrew picked up the socket and
string, I tossed the spool (this was 300' spool) over the 20m beam
second director element and to the ground. The groundcrew
member picked that up and, gingerly pumping the line, he ever so
slowly brought the element back into alignment with the others.
I don't know how long it will last, but since it did not move around
for a year or two, maybe it will stay where it is for a while...until
the next big bird comes along.
Earlier this week, I put a note on the reflector asking for suggestions
regarding how to keep the mast on this tower in place while the rotor
was removed. One of the suggestions I received sounded so good I
used it. It was to take three slotted angle irons, ubolt them, one to
each leg, and ubolt them to the mast. I did this. It worked perfectly.
The mast does not move one iota. (One thing for anyone else who
wants to try this: make sure the antennas are pointing where you
want them to if your rotor is going to be out of service for a while.
Also, I don't know how much torque the angle irons will take before
they start flexing.)
Another of my concerns was the possibility of having to crowbar and
shim up the mast from the rotor in some way. I guess it had been so
long since I was last up there that I forgot what it looked like. The
mast end was a good 1/2" off the rotor. I u-bolted the mast at the
thrust bearing to make sure it did not drop and removed the rotor with
I coordinated with a couple of folks in the club station to conduct a
continuity check of the cable (might as well check that out, too,
while I was there). Using pin 1 lead as the common, each lead in
turn was shorted to the common lead up on the tower. Only the
pin 3 lead showed significant resistance (100-180 ohms), all others
being ~2 ohms. We seemed to have a bad cable.
Once I was at the tower base, and we were discussing the results,
I noticed the rotor cable going up the tower was mated to two
cables coming from the cable conduit (the tower is about 150 feet
from the shack). The interface of the three cables was with a
connector. The juntion was well wrapped and sealed, but while the
tower skirts were off it was as good an opportunity to check that
out as any. Finally, I managed to get the sealer (I don't know what
was used, but it was good and tough to get off) off the connector
enough to pull it apart, I felt we had found our problem. Water
drained out of the connector, green stuff was around a couple of
the pins, some of the pins were no longer restrained in place, overall
it looked really ratty in the connector. Since there was rain
approaching, we taped the cables back together, put the anti-climbing
skirts on the tower and hauled everything into the shack.
Based on what I experienced on the tower today involving the rotor,
I made a few mental notes to do some things that would reduce
confusion, frustration, and potential problems while up on the tower.
Before putting your rotor up on the tower, do a
couple of things first:
1. Make a drawing or sketch of the rotor base as you might
be looking at it on the tower, identifying each pin by number, location
2. Place it with your rotor manual. Make a copy of it to carry
with you each time you go up on the tower.
3. On the tower, and when connecting the rotor cable for the
first time, make a wirelist by pin number and wire color. Keep a copy
with your rotor manual.
4. Write the pin numbers and wire colors in some kind of
indelible felt tip pen under the rotor plate. It may not last for years, but
it may last until the next time you go up and find you have forgotten the
connector pinout list.
5. If your control cable run is a mix of different cables and,
consequently, different colors, make a comprehensive wirelist.
Box cable1 cable2 rotor
1 black black black
2 white red red
3 brown orange orange
Carry this list with you on the tower. Any conversation with the
ground crew or someone in the shack will have to be in terms of
what they are seeing there and what you are seeing on the tower.
I'll be bench testing the rotor this afternoon, once I get cooled
down and relax a bit. I now expect it is just fine; it's the cable
that is the bad guy in this....maybe.
Something else we tried to do with a second tower climber was
to try to assess the problem we are experiencing with an A3S
at 60' on a 50' freestanding tower (military, wide three legged base,
hell to climb until you hit the smaller sections with 'normal' zig-zag
Rohn-type crossbraces). Unfortunately, the A3S is above the
A3WS by about 8 or 10 feet. The other climber could not get close
enough to the A3S to either physically get to the boom/mast clamp
or even visually ascertain whether there was a connection problem
at the driven element.
My thought is to put a couple of large pipe clamps I removed from
the 80' tower today on the mast and use them as a single step
about one or two feet above the thrust bearing and the A3WS.
(The clamps once held the arm for the 40m 2el beam at the 65'
point of the 80' tower) This is pretty iffy, to me, but I thought I
would throw it out here and ask what the consensus was about
this technique. Unfortunately, the array on the 50' tower, like the
array on the 80' tower was installed with a crane. So, we have to
use our silver bullets sparingly.
Overall, it was a good, productive morning. The shack even got
something of a clean-up. A couple of members were even
weed-whacking around the 50' tower and the old, now horizontal
on blocks, W51 tower. They even had a QSO with astronaut
Mike Foale onboard Mir for a few of his astronaut buddies this
Again, I apologize for the length of this, but I thought some of it
might be of interest (concern?) to many on the reflector.
Dale Martin, KG5U
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