On Sat, 25 Jun 2005 15:47:30 -0700, Roy Lewallen
wrote:

Owen wrote:
Roy Lewallen wrote:
. . .
See above comments. Routing the feeder at right angles to the antenna
doesn't eliminate current due to mutual coupling, and neither does a
feedpoint balun.


Roy, doesn't this suggest that there is benefit in twisting an open wire
feedline to attempt to expose each conductor to similar coupling to the
external fields. Clearly the benefit will be better for a higher twist
rate. Whilst achieving sufficient twist rate with a wide air-spaced line
may be impractical, it is probably quite realisable with ladder line
(notwithstanding the downsides of ladder line).

No. The problem isn't that the coupling is different to each conductor
of the transmission line, it's that the coupling is different from the
transmission line to each side of the antenna. Twisting the line won't
change the coupling of this common mode current by any appreciable
amount. Unfortunately.

Yes, of course. Twisting helps differential coupling (which in most
cases of sound installationwill not be an issue by virtue of the
relatively large distance from any other conductors to the feedline),
but not common mode.

Owen
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