Hello Richard,
I see 3 choices:
1. use the single piece of 7', 1.5"OD fiberglass boom from KLM.
feed it through the elevation positioner then add the antennas.
2. Use the M2 3 piece 11' boom, 2 pieces of 5', 2"OD boom and a
solid aluminum center piece that both other pieces fit over.
3. design your own out of standard fiberglass stock.
I prefer the M2 version. The long 2M antenna is farther from
the mast allowing my guys to be higher up the tower. I also have
room for other antennas on the boom such as 1269, 2304, and
a 1' dish for 10 and 24 Ghz...
The split boom is easier to work with. I assemble everything on the ground.
I balance it up from front to rear by sliping the antenna boom to mast
clamps.
I balance from side to side by adding more antennas.....starting with the
70cm side.
After all is balanced, I disassemble the 2 boom pieces from the solid Al
part.
I install the solid Al part in the Yaesu elevation positioner, them add the
boom
halfs one at a time.
Other balancing techniques are possibe. Some prefer to have the front heavy
to hold
the front end down if the positioner has a sloppy gear train... Under this
sloppy rotator
scenario, the heavier it is out front, the more stable the elevation will be
in the wind.
Always paint the entire fiberglass boom at least 2 coats. I used flat black
paint.
Always use a 1" OD x 6" fiberglass dowel inside both ends of the KLM 1.5" OD
fiberglass boom. Epoxy it in place and paint the end.... The M2 2"OD boom is
plenty strong to not require "doweling". The doweling allows more torque on
the
antenna mounting U-bolts with out crushing the fiberglass boom.
If you are real serious, also dowel the area where the elevation rotator
clamps
will be used.Keep in mind, this dowel may be off center to allow the
2M and 70cm to balance.
Always use the gritty traction "sticky back" tape at the areas on the
fiberglass
boom where antennas will be clamped and where the elevation positioner
will be clamped. This tape is usually used on stair treads for increased
traction.
Most hardware stores have it.
If you pick up a used fiberglass boom, inspect it carefully for UV
deterioration
and cracks due to overtorquing the antenna and elvation clamps.
Light deterioration of the fiberglass surface can be recovered with a paint
job.
Mast mounted preamplifiers would best be placed on the vertical mast. Allow
enough
of a service loop on coaxial cables for the full range of elevation and
azimuth travel used.
The Yaesu 5400 AZ and EL rotator system is quite popular. be sure to re-pack
the bearings in the elevation rotator every few years with a tenacious
grease.
These bearing are not protected from the weather, with a seal. Only the
grease
protects the bearings in the elevation rotator.
I believe that Texas Towers at 1-800-272-3467 will sell all you need.
Stan, WA1ECF Cape Cod, MA FN41sr
Richard Parry wrote:
> I need a boom for 2 meter and 70 cm beams. Is a "Fiberglass 7' boom" the
> standard. Suggestions on where to get one?
>
> thanks in advance,
>
> ---------------
> Richard Parry, W9IF - Qualcomm, Inc. Globalstar UT System Test
> <http://people.qualcomm.com/rparry>
> ---------------
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
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