In article ,
Roy Lewallen wrote:

This is a situation that I'd frankly never considered before -- where a
feedpoint balun can actually *increase* the common mode current! The
current can, of course, be lowered to a small value by adding a second
current balun (common mode choke) about a quarter wavelength down the
wire (Wire 6, 50% from End 1).

To coin a phrase: "Fascinating!" Thanks for pointing this out, Roy.

This gives an interesting twist to some advice I'd read several
times... that to choke off feedline current one should install two
chokes or ferrite beads, a quarter of a wavelength apart on the feedline.

I had always assumed that this was simply a quickie way of making sure
that a useful amount of choking reactance was sure to be installed
fairly close to a current maximum, where it'd be most effective, and
that if you knew where the current maximum actually was and put a
choke there, you wouldn't really need to install the second choke.

The fact that the conduction and induction currents behave differently
would seem to rule that out - there really _is_ a good reason to have
two chokes, to handle the two modes.

Hmmm... slightly crazed idea... I wonder if there's a market for a
coax with some amount of ferrite dust mixed into the PVC jacket when
it's extruded, so as to create a self-choking distributed-inductance
feedline. If the more rabid audiophiles can be convinced to spend
thousands of dollars for a one-meter RCA-plug-tipped interconnection,
maybe the excessively- well-to-do ham (there must be at least one)
would pay ridiculous sums for a self-baluning RG-8?

Might be a neat income opportunity, if one could sell it at high
prices and still stand to look at ones face in the mirror the next
morning (I couldn't, but I imagine there are people who could).

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!