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Warning: Installation of antennas and tower climbing can be hazardous to your health.
This information is provided on a as-is basis and naturally, I assume no responsibility
for your safety or how you interpret of implement the techniques described here.
Obtain professional help before installing any tower or antenna.
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The dual tram/trolley requires a lower support, a upper support along with and two
tram wires and two runners. The idea is to captivate the antenna in two dimensions
so it can only go up or down hill along the plane of the tram wires. Antennas
can be suspended above the support cables, trolley mode or suspended below
the support cables, tram mode. This picture shows the 1990 version of the lower
support.
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Current version of the lower support. Note the support cables are of equal
length and are terminated to the lower support using turnbuckles. The turnbuckles
allow for individual adjustment of the support lines. This have proven to be
very useful and allows for the individual tension of each line. Unequal tension
means that one end of the boom will tilt, a technique useful for clearing beam elements
over guy wires. More on this feature later.
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The upper support is bolted to the tower and the two support lines are attached.
The upper support is made of thick wall aluminum conduit. The spacing of the two support
lines should match the spacing used on the lower support, in my case, the spacing
is 44.5 inches. The dual support lines should be parallel.
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Between the upper and lower support, two parallel wires are suspended. Two
runners made of thick walled aluminum tubing slide against the parallel wires. Various
adapter plates are attached to the runners allowing support for popular boom sizes.
Shown is the attachment for a two inch boom suspended trolley mode.
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In 2005, new runners were constructed for raising heaver antennas like the MonstIR.
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Here is a M2 6M7 part way up. The antenna was orientated 180 perpendicular to the
tram lines and the coax is attached allowing for antenna testing.
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Here is a Force12 EF-240X almost up using the tram mode. The top set of tram cables
used pre-formed guy grips. When pulling up a beam, the runner will generally stop
on the guy grip. Do not force it further or you will deform the guy grip. You can
use a large flat bladed screwdriver to adjust the runner where it will slip up over
the perform guy grips allowing the assembly to be pulled the final foot or so into
the tower. Once the beam is in place, you can remove the runners assemblies from
the beam. Its a good idea to tie the runners off to the hoist cable and lower them
to the ground. The ground crew may get a little nervous if you allow a lose runner
to slide down a tram.
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Here's one of the Force 12 CX31's headed up using the tram mode. This antenna was
left 1/3 of the way up the dual tram for a week, waiting on the winds to die down.
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Here's a more detailed view of the CX31 using the tram mode. The CX31 has
a lot of elements close to the tower so it gets a little crowded. Pay close attention
when raising elements that are mounted close to the tower so they fall into the
correct space. I had one element try to place itself inside the tower. If
you think you may have issues with elements close to the tower, you can always add
them once the antenna is mounted on the tower. This is a good option to consider
if you think you may have issues with a close in element clearing a guy.
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Now for the big one. The antenna is a 3 element full size 40 meter Telerex 40M346
antenna on a 46 foot boom. The weight of the antenna is 177 lbs. The longest element
is 64 feet and the wind surface is 14 square feet. The turning radius is 40 feet.
This is a shot of the antenna going up using the tram mode in Colorado
in 1990.
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This is a shot of the Telerex 40M346 at the top of the tower. Another technique
that I have used is, when the antenna gets to the top of the tower, slack off the
tram lines and just let the antenna fall into the tower. This works very well on
the larger antennas. Also, I use two come-alongs at the top of the tower to fine
tune the antenna into position. One of the come-alongs is modified with rope which
makes it a nice light-weight tool for moving antennas into their final position.
You are not going to move a antenna of this size very far, from my experience where
it lands is where it gets mounted. At the top of the tower is a Hygain 205, a KLM
15M6 and a KLM 10M6 (not shown) also erected with the dual tram.
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This shot shows the main rope used to pull the antenna up the tower. The main pull
rope runs to a pulley located at the upper support and then down to the base of
the tower to a second pulley. Light beams are generally pulled up by hand and the
heavier beams pulled up using a small riding lawnmower. A second rope is attached
feeding off a lawn hose reel, allowing the assembly to be pulled back to the ground.
This is generally not needed as gravity works well but its there just in case. You
can see the dual tram wires running to the lower support in the background.
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Antenna assembly can be done on saw horses or in my case I use a trampoline. The
antenna is assembled on the trampoline and the dual trams are connected along with
the hoisting rope. You slowly back up the lower support, i.e tractor, and the dual
trams lines tension and raise the antenna off the trampoline. Watch the longer beam
elements so they do not deform if they hit the ground. Caution: Watch the
tension as you can pull the tower over if the tension gets too tight. Depending
on your installation, you might want to run a back-guy off the top support to help
counted tension from the lower support.
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One of the big issues with any antenna installation is clearing the guys. If you
use two turnbuckles on the lower support, you can vary the tension and actually
rotate the boom. For this picture, the tension was intentionally adjusted to show
how much a Force12 EF-240X boom could be moved. This technique is very useful for
getting long 40 meter elements over guys. Its also useful to have ropes tied of
each side of the boom allowing further boom adjustment from the ground. Another
technique that has been used is rather than send the antenna elements up parallel
to the tram cable, increase the angle of the elements. This is easily controlled
when you attach the runners to the boom. Also keep in mind that you can slack off
the tram cables and increase the angle.
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The dual tram rolled up and ready for its next project. In the summer of 2003
it was used to take down a pair of stacked Force12 CX31's, 3 M2 6M7's, a Force12
EF-240X. Since that time, its been used to put up a pair of KLM 15M6's and
a pair of KLM 10M6's as well as a pair of SteppIR's. In 2005, the dual tram was
used to raise a MonstIR antenna at W5SL's QTH.
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John, WE2F, has built a slight variation of the dual tram.
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The WE2F tram variation is action.
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