dykesc wrote in
ups.com:

On May 10, 4:14 pm, Owen Duffy wrote:
Owen Duffy wrote
:

What have you done to make the 259B appear as an isolated impedance
meter?

I did mean to add that in this case, the impedance at the end of the
isolated feed line is not necessarily (and not likely to be) the same
as when it is connected to your transmitter. Again the same issue
arises about the path to ground for common mode current, and the
influence that has on the antenna feed point impedance transformed by
the transmission line.

You need to think about the purpose of the measurement.

Owen

One more question Owen. If I measure the complex impedance on the low
side of a 4:1 current balun. Is the impedance on the high side simply
4 times the low side? Can I just multiply the resistive term by 4 and
the complex term by 4?


If the balun was ideal, you could do that. To the extent that it isn't,
error will be introduced.

I think some of this comes back to the question "what do you want to
know".

If you want to know the load as connected to your transmitter, simulate
that connection including baluns, earth connections etc.

If you want to make an isolated measurement for some reason, I would have
expected that the 259B on batteries at low HF frequencies and supported
clear of other objects would be sufficiently isolated to not get the
differences you observed.

My suspicion is that if you follow the calculation path you described,
the inherent range / accuracy of the 259B will be a problem, and the
precision introduced by the measurement approach will be lost due to
instrument error, indeed you might be worse off.

Owen