[TowerTalk] Old beam

[dan hearn]

I picked up an old TH3 myself a couple of years ago and rebuilt it. I
believe that the 259B is of little use in testing individual elements
when they are near the ground or surrounding objects(including
yourself). From your description I suspect your beam may need a
mechanical rebuild. My beam had cracked plastic trap ends and when I
removed those, most of the plastic centering discs inside were not 
usable. I ordered new parts for those. The trap insides were full of
bits of grass left there by spiders I am told.The wire coils were
brushed clean and the sheet metal screws at the coil/element junctions
were removed. This area was cleaned and a small amount of Alox was
applied there and on the threads of the screws. 
 Unfortunately, the original clamps for element joints had 1/4 inch
bolts with pointed ends which indented the aluminum in a dimpled
fashion. The joints could not be separated by removing the clamps. I
hope you do not find this to be the case with your beam.I had to use an
abrasive grinder to cut off a short piece of the outer tube at each
joint and peel it off. I was able to put in some short pieces of new
tubing (purchased from Texas Towers)at the joints after making hacksaw
longitudinal slits. Needless to say, I used regular spiral hose clamps
in the rebuild. 
  Element joints were cleaned with small gun barrel cleaning wire
brushes in a rotary drill.I have also used a short piece of 1/4 inch rod
in my drill to do the same job. Just cut a short hack saw slot in the
end and insert a short piece of emery cloth in the slot. Centrifugal
force will cause the ends of the emery cloth to fly out cleaning the
interior (the hard part, Hi). Be sure you turn the emery strip ends in
the right direction so the abrasive side is out. Alox was applied to the
clean surfaces.
  I sent the rebuilt beam to my son, who lives on an island off the
coast of Washington in a pretty corrosive environment. He set the
lengths per the instructions , and it works FB. I believe he told me one
band has the low SWR point off center in the band but the others are
right on.

73 and GL, Dan, N5AR

Ron Feutz wrote:
> 
> I have located an old HyGain TH3 MK3 tribander.  It has been lying,
> disassembled, on the ground for 15 years.  How can I use my MFJ 259B to
> check the elements for proper resonance?
> 
> Ron - WA9IRV
> 
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