The sign of Return Loss





where Z1 and Z2 = the two impedances.



Return Loss according to the miniVNA Tiny



What is plotted and labelled Return Loss is actually the magnitude of S11 or |S11|.

What is RP

The parameter RP had me guessing… was it equivalent parallel resistance component? It does look like it may be the phase of S11… Return Phase? That’s a new term.

If we take the reported Z at the marker to be 61.0-j3.0, we can calculate various other values.


We can see above that |S11| is 0.1027 which in dB is -19.77dB. The phase of S11 is -13.7° which reconciles with the minVNA RP parameter at the marker.

It does look like the miniVNA world is one of an alternate nomenclature and alternate meanings to the mainstream.

Little wonder hams learn bad practice from instruments that should be an example of what is right rather than what is wrong.

PS: the same software plots TL (Transmission Loss?) though a passive device as negative… wrong sign again, probably caused by not understanding S parameters and the fundamental meaning of Loss, then labelling |S21| as TL.

Links / References

    IEEE. 1988. IEEE standard dictionary of electrical and electronic terms, IEEE Press, 4th Edition, 1988.