"Richard Clark" wrote in message
...
On Mon, 4 Oct 2004 19:30:19 -0500, "John Smith"
wrote:
400 5.1 + 1.3i
Reference Measurement
Freq A1 B1 ?1 A2 B2 ?2
400 1 0.79 180 1.08 0.695 177

Hi John,

Well, from the two results above, and referencing my copy of Appl.
Note 77-3, Page 7, section "Measuring Rho 100 to 1000 MHz," there are
a number of issues here.

Your B1/A1 is quite off the mark (but certainly correctable, afterall,
that is the purpose of its measurement).

|Rho| = B2·A1/A2·B1 = 0.695·1/1.08·0.79 = 0.815

Casting the magnitude and angle onto a Smith Chart would suggest your
5.1 + 1.3i Ohms is close enough given your data.

The only kicker is port tracking, but I have a hunch that probably is
not an issue.

This bears further consideration. Too bad Kraus did not choose to
elaborate.

73's
Richard Clark, KB7QHC


I don't understand. Please enumerate the issues. What do you mean B1/A1 is
off the mark? If they are off the mark, how can the Z be close enough?

Are you saying that I have calculated the Z correctly from the data and you
think port tracking is not at fault? What further consideration?

You're right. Too bad Kraus didn't tell the feedpoint impedance. I suspect I
would not have embarked on this folly if he had. The antenna may have its
uses elsewhere, but I don't need the headaches of matching 5 Ohms at 440
MHz.

John