On Sun, 22 Oct 2006 18:01:24 +0100, Ian White GM3SEK
wrote:


Cable is much less expensive over here than large ferrite beads imported
from the USA; hence my interest in the coiled cable chokes.

The cost of cores from imported from the US in Australia is also very
high.

For those in Australia interested in W2DU style baluns, I roughly
measured the impedance of an inexpensive core from Jaycar using a
Mighty Fine Junk 259B and plotted the results at
http://www.vk1od.net/balun/index.htm . Less than A$20 is probably
sufficient for an adequate balun for 80m to 10m.... depending...

My own view is that the number of cores required for a W2DU style
balun is unrelated to the characteristic impedance (inner to outer
conductor) of the coax as is commonly held, but that the number of
cores / effectiveness varies with location on the feedline and is
highly dependent on the scenario (frequency, topology etc) and the
optimum solution may required more than a single choke.

Ian, perhaps low cost suppression cores are also available directly in
your country, candidates for measurement and reporting!

Owen

PS Interesting plots, better presentation isn't it, the Y axis label
on your phase graph needs a fix.
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