Jim,I have a US Tower HDX572 72ft telescopic tower with a DB42 at the
top and a 3el steppIR on a side.
When came the time to install the cables I passed through the same
questions as you are asking.
I am living in Montreal and it was very interesting if not funny to see
how people in the South were just considering leaving the cables on the
ground when the tower is in the low position. Here, during the winter if
you leave the cable lying on the ground within a few days if not hours
the cables will get stuck into the ice and you just have to wait the
spring before being able to extend the tower again.
So, after several tries I finally found the solution. It will be faster
to explain it with pictures so have a look at the following link :
https://drive.google.com/file/d/0ByGzx2yN6nC3QzY0clpyUmtoV1E/view?usp=sharin
where you can upload a PowerPoint in pdf format.
Please visualize the pdf in full screen not just on the web site in
small format. I have extracted for you and other interested hams a part
of a presentation that I did to some local clubs about the installation
of the tower.
First I did a scale 1:1 simulation of the top of my tower to determine
the length and path of the cables when the rotor is moving on 450 deg.
That reproduction had also helped me to write a procedure to install the
DB42 on the tower. You can "run the movie" in both directions my pushing
the arrow keys.
A Second part shows how I have attached the cable on the standoffs. The
very important thing is that with the numerous moves up and down that
you will do, if the cables are bonded directly to the standoffs the
cables will be bent with a too small bending radius and are going to
break by metal fatigue. So to keep the cable out of the minimum bending
radius I invented a simple system consisting in attaching the cables on
small metal plates which are rotating around the standoffs. That way the
cable and plates are articulated and are rotating while the tower is
retracting respecting a loop shape.
Third, you must arrange the cable loops in a way they cannot pass into
each other neither pass around any standoff. Otherwise you will live
catastrophic experience of teared out cables and standoff. On the last
pictures of the pdf, as for the rotor simulation you can "run the movie"
of the tower retracting and observe how the cables are turning from a
straight line to loops while retracting.
Then in any position of the tower you have a clear tower and never the
cable will lay on the ground.
Enjoy
Gilles VA2EW / VE2TZT
On 25/12/2016 14:04, Jim George wrote:
I've had a three-section crank-up tower (it used to be called the
LM-354) that's 54 feet tall when fully extended. For a long time, I
used it in a permanent fully-extended manner, with phased ten meter
yagis at the top and half-way up. Now, it will have a triband yagi and
a two-element 40 yagi on it, above the thrust bearing, and I wish to
keep it at least semi-nested between contests to avoid storm damage.
What is the recommended way of bringing down two the coax feedlines
and the rotator cable for a tower that will go up and down fairly
regularly? I'm going to use the three original "stand-offs" to keep
the coax and the rotator cable hanging vertically as these three
standoffs are positioned such that they nest properly when the tower
is down. Is it okay simply to hang the feedlines and the rotator cable
down through the top standoff, which seems to rotate around as the
rotator moves the mast, and simply let the coax and cable drop down
vertically? In this case, there would be no traditional rotator loop.
That configuration has worked okayrecently with only the small 40
meter yagi on the top.
Another possibility would be to form a five or ten foot "rotator loop"
with the feedlines and rotator cable and then route them back up onto
the top standoff and down vertically through the other two. In this
way, the system would not require that top standoff to move around on
its tower leg as the mast and antennas rotate. Not sure if I described
this in a clear way. If I were sure that the top standoff would move
around on its tower leg, that would work, but if the top standoff got
stuck and didn't move, then the feedlines and rotator cable could get
stretched and damaged. For some reason, I haven't seen anything on
this, or have forgotten. Any recommendations?
Thanks in advance, and all the best at the Christmas and other holiday
breaks and new year.
73, Jim George N3BB
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