> Can anyone tells me what happens? Should I be using a
> current-type balun
> ala' W2AU or should I wind the choke? If so, what size is
> it?
At six meters I'd use a sleeve balun of beads (like 43
material several inches long along the cable) and then tape
the cable to the boom after that point.
You could simply space the coax an inch or so above the
boom away from the feedpoint for just slightly under 1/4
wave and then ground the shield to the boom. Years ago I
designed some TV antenna feed systems for single channel TV
antennas and the spaced feedline worked very well in actual
measurements!
Be careful about other schemes. For example a 1/4 wl sleeve
or Bazooka is highly dependent on the ratio of coax shield
to inner diameter of the sleeve, and there must be a good
air gap inside in order to have significant choking
impedance. It's certainly possible to build a good one, but
it would be a lot of work to do it right on six meters.
> Part deux. In my meager understanding, a balun is a
> transformer that
> goes from balanced-to-unbalanced (bal-un, get it?)
> vis-a-vis a feedpoint. It
> also functions as an RF choke to prevent RF from spilling
> down the outside of
> the shield. A coax wound RF choke doesn't really
> "transform" anything but does
> choke the stray RF trying to come down the outside of the
> shield. Am I close?
Yes. The important part is it have fairly high common mode
impedance.
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