On Apr 15, 11:30 pm, Alan Peake
wrote:
Jim Kelley wrote:

I guess I may have been 'intuiting' too much, myself. Since virtual
shorts and opens only appear in the steady state, I wouldn't expect
pulses to reflect off of them. I don't expect sine waves to reflect
off of them in steady state either for that matter, but that remains a
point of contention apparently.

73, Jim AC6XG

Actually Jim, virtual shorts etc. act the same for pulse systems as for
CW systems.

Hi Alan -

Reflections measured by a TDR are caused by physical impedance
discontinuities. Virtual impedances are defined by the superposition
of forward and reflected voltages in the steady state. Pulsed systems
offer the ability to study the transient effects of a system by
viewing reflections caused only by changes in the characteristic
impedance of the transmission line. Since TDR doesn't use CW (not to
be confused with Morse Code) it does not operate under steady state
conditions and can therefore neither prove nor disprove the claim for
reflections from virtual impedances.

73, Jim AC6XG