Good question.
My experience is with TWO 70ft crank up towers, HyGain and US Towers, both
motorized, over 28 years I used the stand-off arms at the TOP of each
section to allow full retraction.
I routed the bundle of coax-s and rotor cable through the rings at the end
of the stand-off arms freely up to the very top of the tower where it was
taped to the tower fully. The rotor cable went out of the bundle to the
rotor there.
The coax bundle, taped together, formed a modest coax rotor loop, only long
enough to allow full rotation and not droop down and wind up on the tower
top. (Some Yaesu rotors require a larger loop for 450 degrees of
turning.) The coax is then taped to the mast and on to each antenna
upward.
This method puts the load of the down-going coax bundle on the top tower
tape attachment because the rest of the bundle is free through the
stand-off arms. Do not use an arm to rotate along with the mast due to
complicated loop flopping around badly.
For a while, I did measure the coax bundle and tape it firmly to each
stand-off arm, allowing for full extension, but I found the coax could, and
did, flop inside the tower as it came down, endangering the coax... thus I
left the best method be free all the way downward.
I use wide, black cable ties on top of the tape, snugging it so as not to
deform the coax. I keep the coax-s taped together full length.
Works with 70ft tower also. 73, Charly
On Mon, Dec 26, 2016 at 2:04 AM, Jim George <n3bb@mindspring.com> 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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>
--
Charly, HS0ZCW
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