RadioBanter - View Single Post - Need further info on network analysis terms...

May 3rd 06, 03:23 AM posted to rec.radio.amateur.homebrew,sci.electronics.design

On 2 May 2006 15:14:29 -0700,
wrote:

Hi gang,

Reading through the instructions for this VNA it mentions some
important accessories; power spitters, 6db attenuators, 50 ohm
terminations, opens, shorts and throughs. What exactly is a "through"?

A through is a direct connection of the two test ports (cables). If
all devices under test (DUTs) were "insertable", i.e. had one male and
one female connector (or GR or 7mm sexless connectors) then the test
port cables could be joined directly, thus forming a through ("thru")

Unfortunately, a lot of DUTs have the same sex connector on both
sides, thus a calibration thru must be a double, same sex adapter
(barrel). Using such an adapter during calibration adds some
unavoidable length (and loss and mismatch) to the test path length.
One method of removing (some of) the effects of the barrel is to
replace it after calibration with a matched length male-female adapter
that remains in the test path.

And is it possible to make up accurate opens and shorts oneself that
are good enough for calibration purposes up to 1.3Ghz? Not talking
about any absolute standard here, like you'd get from HP themselves;
but just mid-tolerance stuff that'd be sufficient for reasonably
accurate amateur experiments?

Depends. For SMA stuff, an open and shorted connector wouldn't be too
bad. Type N is a little more problematic but probably doable for
moderately accurate measurements.

BTW, even HP (Agilent) doesn't offer "absolute" standards. :-;