You haven't mentioned a balun at the 259B, or any other device to float
the measurement terminals to make a true differential mode impedance
measurment without significantly disturbing the thing you are measuring.

There are issues regarding balance of the feedline with an OCF dipole,
but reversing the meter for different readings suggests that the meter
terminals are not sufficiently isolated from the environment (ground, the
adjacent transmission line, possibly a power cord).

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

Owen

Owen,

My recent experience and your post has convinced me that a direct
termination of my balanced transmission line (300 ohm twin lead) to
the 259b is going to be problematic. I am now measuring through the
4:1 current balun in my MFJ tuner. Wish I had a 1:1. At 7.185 Mhz
through the 4:1 balun (tuner bypassed) I get 19 -j48. Assuming an
ideal balun I believe your previous post stated this would be 76 -j192
on the high side. At most even harmonic frequencies I've measured, it
appears the 4:1 balun in the tuner is actually resulting in too low a
resistive term impedance. As I write this I recall some text in the
antenna book about calculating the proper 1/4 wave Zo transmission
line impedance needed to transform to a desired impedance. Will this
work for any odd multiple of a 1/4 wave transmission line? On second
thought this wouldn't work on the harmonics would it? If I set it up
for 20 meters it wouldn't work on 40. The whole deal with the off
center feed is to be able to use it on even harmonics (80, 40, 20
meters). Guess I'll just work on figuring out the best compromise
transmission line, but I'm fairly convinced I can do better than the
300 ohm twin lead.

This is all just for the challenge of understanding the theory and
making it work in application. The tuner is doing fine for all 3 bands
in my current configuration.

Thanks for helping out a Stuggling Crippled Newbie Street Urchin.