On 11/28/2020 2:10 PM, Edward Mccann via TowerTalk wrote:
Thanks Jim:
But not sure which your “yes” addresses, part 1 or part 2?
1. “If I use the VNA with direct input of ladder line, say nominal 450 ohm Zo, but
with measured parameters more near 400 ohms, should I not run OSL calibration with a 400 ohm
load prior to running the sweep?”
NO! We are calibrating the analyzer to the measurement plane, which can
be it's input and output terminals, or it can be a pieces of 50 ohms
coax attached to one or both ports.
If I'm not mistaken, the SARK is a VIA, not a VNA. -- A VIA (Vector
Impedance anzlyzer) has one terminal, only measures S11. VNA a(Vector
Network Analyzer) has input and output, can measure all four
S-parameters (so it can measure the gain/loss of a two-port device).
2. “The response below seems to imply that calibration with a 50 ohm load will yield
“good results for coax and two-wire line of any impedance?”
That's exactly what I said.
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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