I have to agree with Dick. I can visually observe one of my towers and
the cables from my shack window. The other one is 300 feet away and
visible through another house window but not from the shack.
Nevertheless, I generally only LOWER the towers remotely. We get some
heavy duty winds here in the winter that arise unexpectedly and, more
often than not, at 3:00 AM in the morning. I have spent too many
miserable episodes standing in my bath robe in the snow, wind and
freezing cold lowering the tower at those times. Typically, I raise the
towers using the local switches.
My original point in commenting was to let the questioner know that
there was a relatively cheap alternative to the Tri-ex remote control.
I believe that is sells for around $1,000. Since I am using precisely
the same kind of M-O-M switch in the shack that was originally supplied
by Tri-Ex for the tower control box, I see no difference between
operating it locally or remotely (other than the inherent risk of some
kind of unobserved cabling or other mechanical snafu).
73, Joe
K2XX
Dick Green WC1M wrote:
> K7LXC wrote:
>
>
>> Yeah, don't do it. The only way to insure that a
>> crank-up goes up or down successfully is to be in the direct
>> vicinity - preferably standing next to it - watching it as
>> it's moving. Otherwise a cable can snag and the result can
>> be breaking a haul cable and watching the whole thing crash down.
>>
>
> Well, some of us have to do it. My crankup tower is 265' from the shack
> behind a tall stand of trees. If I squint real hard, I can sometimes see one
> of the antenna elements through the foliage. But most of the time I can't
> see anything until the antenna is nearly at max height. Every year, as the
> trees grow, the amount of tower I can see diminishes. Pretty soon, I won't
> be able to see it at all.
>
> For a number of reasons, I use my crankup very sparingly -- pretty-much only
> for major contests and for hunting very rare DX (only need two more
> countries, so that doesn't happen very often.) I could probably live with
> standing next to it when raising or lowering it, but I want the option to
> lower it immediately when the wind speed gets too high. Every now and then,
> I need to raise the tower when there's snow up to my waist and it wouldn't
> be much fun trudging down a steep hill in the dead of winter to raise the
> tower, especially at night. Same is true when there's a big rainstorm. There
> are just some occasions when I want the option of operating the tower from
> the comfort of my shack.
>
> But Steve is right that remote control is a potential tower-killer. Nine
> years ago, just a couple of weeks after I got my U.S. Tower MA770MDP
> installed, I was demonstrating it to a friend. It was October, the leaves
> had fallen, and we could see the tower rising through the trees. When the
> tower got near to the full-up position, it started swaying violently back
> and forth. And I mean violently! For a couple of seconds I was completely
> stunned and didn't know what could be happening. Suddenly, the violent
> swaying stopped. I shook off the shock and hit the OFF switch real quick. I
> knew something terrible had happened.
>
> Upon examination, I found that, despite using standoffs, the coax had
> migrated around the tower and had gotten snagged by one of the brackets on
> the back of the utility box containing the tower control electronics. About
> six inches of the coax jacket had been gouged off. The coax underneath was
> crushed. I looked up, and saw that the coax had pulled out of the balun on
> the TH-7. In fact, the balun had exploded. This was lucky. Basically, the
> plastic balun housing failed, releasing the SO-239 connector and saving my
> tower before the steel cables or pulleys failed, or before the motor burned
> out.
>
> I determined that the failure was caused by several related factors. I had
> positioned the coax standoffs at the top of each section. The motor and
> control box were mounted at the middle of the bottom section, well below the
> last standoff. The lack of a standoff below the motor mounting point allowed
> the coax to move around the tower. This was compounded by using Times
> Microwave LMR400UF, which is anything but "Ultra Flexible". The stiff coax
> bent into a huge loop as it hit the ground, and walked itself around the
> tower to the motor and control box. I also had the standoffs less than 180
> degrees from the motor, reducing the distance the coax had to travel.
>
> The solution was to put standoffs above and below the motor (especially
> below.) That way, the coax could not work its way around the tower. I
> repositioned the standoffs 180 degrees from the motor, allowing the coax to
> "flow" downhill away from the tower. I also switched to much more flexible
> RG-213 (I later switched to Buryflex, which is even more flexible than
> RG-213 and has lower losses.) Finally, I built a cage out of hardware cloth
> to encase the bottom three feet of the tower, where the coax might snag on
> the rotor, rotor shelf, rotor mounting bolts, anchor bolts, tower base
> plate, etc., etc. I ran the tower up and down dozens of times to make sure
> there was no way the coax could snag anything. The coax sort of bounces off
> the hardware cage and coils on the ground.
>
> I've not had any more snagging incidents over the intervening nine years.
> I've watched the coax coil and uncoil many times, and I'm satisfied that
> it's safe to raise and lower the tower without being present. One caveat: in
> the winter it's possible for the coax to get buried under the snow, and for
> the snow to develop a hard crust. I make sure to check for this whenever
> conditions warrant, often having to pull the coax out from under the crust.
> The ice has never been thick enough for this to require much force, and I'm
> satisfied that even if the tower pulled on the coax the only damage might be
> to the coax itself, and not the tower.
>
> So, if you don't have to operate your tower by remote control, don't. But if
> you have to do it, be meticulous in how you deal with all the potential snag
> hazards.
>
> N.B. Some may be wondering whether I attached the coax to the standoffs or
> let it drop through. U.S. Tower has no guidelines for this, though an old
> Wilson manual I have shows the coax tied to each standoff. I tried doing
> that when the tower was first installed, and it was a no-go. This caused the
> coax to form itself into big loops between the standoffs, which would then
> twist around on themselves. That was a snagging hazard in itself, as was the
> very real chance that one of the loops could get caught on a pulley. The
> only rational solution was to tie the coax to the top standoff and let it
> drop through the lower standoffs. This has always worked fine.
>
> 73, Dick WC1M
>
>
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