All,

The system is a vector network analyzer and a coax feedline. The
analyzer does not have built in 'electronic line length' compensation.
So to compensate for 'near' frequency measurements I have created coil
of coax on the floor. The theory is when actual measurements are made on
the antenna the phase can be normalized by zeroing the phase to the
reference coax.

The issue is: Attempts measure the electrical length yield inconsistent
results.

The first step was to determine the approximate length. This was done by
setting the sweeper to a frequency and counting the phase inversions to
the antenna feed - open ended. Lengths of coax were laid out on the
floor until the phase inversion pattern was 'very close' visually.

Next the the frequency was set to 200 kc sweep at one meg on the
antenna. A near phase inversion was centered on the phase display.
Lengths were added or subtracted to the reference coax to get the same
center inversion. (The inversion baseline was verified by looking at a
larger sweep for reference.) So far so good.

Next the same thing was done at 10 meg. A slight modification to the
baseline coax.

Finally the system was retested at 1 meg. Whoops. It was off.

The differences were small, 6 to 8 inches out of an estimated 125 feet.
However it is not possible to get a common match between 1 meg and 10
meg - hence the anomaly.

The reference coax is coiled on the floor. Is it possible this created
an inductance which affects phase?

Thanks - Dan