That doesn't work. No matter how you choke the analyzer connection to the
computer, it is still an unbalanced load. And you must consider it as a load,
particularly if you're using an open/short load s11 method as described by
Chipman or you're measuring a line of significantly different impedance from the
measurement system impedance. In either event, the msmatched load is also a
generator for the reflected waves and the analyzer is an unbalanced load for
those reflections.
I thought to update my ladderline work using lower frequency instruments than
what I had available 30 years ago. I have several VIAs and a couple of VNAs.
Three of the VIAs, are battery-powered and I thought that would solve the
unbalance issue. It didn't; I got wildly variable results until I started adding
a bead balun (I know you don't like that word). I ran out of beads at 32" of
RG142 and it was still not enough at 2 MHz. At that point I gave up and moved
on to more interesting things.
Wes N7WS
On 11/28/2020 6:14 PM, Jim Brown wrote:
The potential issue with 2-wire line though is that if the analyzer is running
from a computer, it can unbalance the line, so it should be seriously choked
and floating from anything grounded.
73, Jim K9YC
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