On Fri,8/5/2016 11:03 PM, Richard (Rick) Karlquist wrote:
No, this isn't the real deal. A 2 port vector network analyzer
with full 2 port calibration is the real deal. The wattmeter
approach has many error effects that are difficult to account
for.
Right. I've never considered using wattmeter(s) to measure loss in coax.
Now I use a DG8SAQ-designed VNWA (vector network analyzer). Very good
accuracy.
Before that, I used an HP generator as a source and an HP Spectrum
Analyzer as an RF voltmeter. Using that for measurement, I could clearly
see variation in the apparent loss below 2 MHz -- this was as a result
of the mismatch between this coax (Zo of a real line is complex and
varies with frequency) and the constant 50 ohm load and source
terminations. BTW -- I was measuring a sample about 1,200 ft long.
73, Jim K9YC
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