On Wed, 20 Sep 2006 17:23:49 GMT, Paul Monaghan
wrote:

Just one question about this antenna - how would one estimate the
impedance? I don't have an impedance analyzer. I have read in this NG
that the impedance will be roughly 300 Ohm, and that a TV-type balun
would bring it down to 75, which would be better than 300 if not
ideal. I have read elsewhere that it will be roughly 75 Ohm and no
balun is necessary. What is the truth?

The truth is that a scanner that covers a wide range of frequencies
rarely shows 50 ohms, and that's only over a very narrow frequency
range, so I wouldn't worry about it. Putting on a balun may improve
reception on some frequencies, only to degrade it on others.