> My questions: should a 1:1 balun be used at the beam or is that not
> recommended?
Absolutely! I have two friends with TA-33's. This is a balanced antenna with
a simple dipole feed driven element. The coax line is unbalanced. You need a
simple but effective choke balun as Tom already pointed out.
Here's how you make it:
The instructions that my friend got from Mosley recommended 6 turns with no
spacing at 6" diameter, wound helically like a spring. His beam is also an
old one, reconditioned, and now packs a punch! We made the baluns starting
with 4 loops of Scotch 33+ to hold the turns together, then wrapped the
entire coil so that it became a solid unit. Don't pull the tape too tight or
you will cause the turns to bunch up.
This is recommended for RG-213 coax. If you use a different type of coax,
be sure that the minimum allowable bend radius is 3 inches or less. If not,
go with a correspndingly larger coil diameter or use ferrite beads instead
of a coil as someone already mentioned.
Be sure to dissassemble all the traps and refresh the coil termination
screws. Back 'em out a little and tighten them back down. A touch of
antioxidant paste between the screw head and the eye formed in the end of
the coil wire would help preserve the electrical contact. We went round 'n'
round unsuccessfully with one old TA-33, trying to get the swr down until we
did this. Three of the old coil forms had cracks and a couple of turns were
separated a little, but the indicated swr was fine.
Another 'gotcha' to watch out for: The old instructions said that there
were color coded stripes on the coil assemblies that were supposed to be on
the boom side....welllll they were marked on the tip side instead! Oops!
There I go reading the 'destructions' again. The SWR was worse! We studied
the illustration, which lists the number of turns in each coil, and shows
the coil orientation. This got our traps oriented properly.
--...MARK_N1LO...--
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