[TowerTalk] Open wire measurments

[Paul Christensen]

Wes,

"As has been suggested elsewhere in this thread, you might be tempted to try connecting the balanced line to the unbalanced test port of the analyzer, in the belief that since it is a "floating" device it's also "balanced".  This has not worked for me."... "So the line radiates; it's part transmission line and part antenna."

No argument there, but that doesn’t mean the CIA cannot report back a valid impedance measurement.  I have yet to find an instance where it hasn’t worked with a complex Z on a balanced line.   I routinely reverse the balanced termination on the unbalanced reflection port and achieve the same result.  Moreover, I obtain the same (or nearly the same) result when using a 1:1 Mini-Circuits RF transformer, then OSL calibrate after the transformer.  By contrast, I often cannot obtain identical results when changing line polarity when: (1) using a "bench" type VNA device where powering comes from electrical mains; and (2) a transformer isn’t used.  

Paul, W9AC