Dennis,
your 4-inch spaced open wire is pretty high impedance. Is
that really what you wanted? For example, assuming you
used AWG #14 wire for the parallel conductor transmission
line, that calculates to Zo = 580 ohms.
Further,
two types of transmission lines will yield different
results regarding the low SWR frequencies. I'm not
surprised the low SWR frequencies were different for the
coax and the open wire feeders. This is expected. I'd
recommend using SimSmith to take out the effect of the
transmission lines. Knowing the measured impedance
(complex) at the end of a particular transmission line,
you can put that in and add that length of line to observe
what each line does no the Smith Chart (resulting
impedance at the antenna).
I'd
leave the 4:1 out of the measurement picture. Connect the
transmission line directly to the S11 port of the NANO.
Operate the NANO on battery and connected to NOTHING, not
even your holding the NANO. Be sure it is sitting on a
non-conductor and well removed from close-by conductors.
At HF frequencies, the measurement will be quite accurate
and will not includ the 4:1 which may not be required in
practice.
Dave
- WØLEV