Topband: Handheld Impedance Analyzer
jim at audiosystemsgroup.com
Tue Mar 29 02:07:51 EDT 2016
On Mon,3/28/2016 10:29 PM, Henk PA5KT wrote:
> You can calibrate it with your feedline connected so you do real
> antenna measurement.
One point of clarification. If you make a measurement that accurately
provides magnitude and phase, including the SIGN of the phase, then
accurately determine the electrical length of the feedline and subtract
it out with correct math, that measurement is just as "real" as if you
took your analyzer to the antenna and measured there with a zero length
cable. In other words, there is nothing "better" about measuring at the
antenna if you made the "in the shack" measurement correctly and
transformed it correctly.
I've done it both ways -- W6GJB was on my tower working on a monoband
Yagi for me, I set up my VNWA at the base of the tower, calibrated it to
a piece of coax long enough to reach Glen on the tower, and measured the
antenna. Later, I measured from the shack with a much shorter piece of
coax to the line, and transformed the measurement up to the antenna. I
got the same data for the antenna from both measurements.
73, Jim K9YC
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