On Tue, 22 Mar 2005 11:06:06 GMT, Nigel M wrote:

I reckon I can use Excel to draw one, but I'm not sure about finding the
focus, other than by measurement.

Hi Nigel,

You aren't going to find a simpler method than the one I described and
Dale has already given you the range to match dimensions against.

73's
Richard Clark, KB7QHC