Wayne wrote:
"John S" wrote in message ...
On 7/7/2015 1:44 PM, wrote:
Ian Jackson wrote:
In message , Jerry Stuckle
writes
Sure, there is ALWAYS VSWR. It may be 1:1, but it's always there.
If there's no reflection, there can be no standing wave. So, being
pedantic, there's no such thing as an SWR of 1:1!
Despite the name, VSWR is defined in terms of complex impedances
and wavelengths, not "waves" of any kind.
Actually, VSWR is defined as the ratio of Vmax/Vmin.
That's also my understanding of the definition.
That is one definition.
In fact since SWR is defined as the maximum to minimum voltage ratio, the
"V" in VSWR is redundant.
There are other kinds of "SWR", but you will never see them refered to
in Amateur literature.
But, using the voltage ratio definition, you can work yourself back around
to various source and load impedances, reflection coefficients, etc.
Or you can start from source and load impedances.
The whole Vmax/Vmin definition is a leftover from the early days when
RF measurments were done on Lecher lines or slotted lines and you
actually looked for the min and max points on the line.
I doubt few under about 50 have heard of slotted lines or Lecher lines
much less ever used one.
--
Jim Pennino