"Reg Edwards" wrote in message
...
What all you experts have forgotten is that SWR on a
lossless line is the ratio of two voltages, max and
min, SPACED APART BY 1/4-WAVELENGTH. That is if the
line is long enough to contain both a max and a min.

When the line is not lossless, ie., it has appreciable
attenuation in dB per 1/4-wavelength, then the ratio is
'distorted' and has a phase angle. So negative values
of indicated SWR can be expected at some values of |
Vmax | / | Vmin |

SWR is calculated from the square of | rho |. As

VSWR is defined as |Vmax|/|Vmin| and so can never be negative. in lossless
lines this expression can be reduced to a function of rho, but that method
is not valid in lossy lines. VSWR is not a constant in lossy lines and
probably doesn't really mean much of anything as each voltage maximum and
minimum is a different value, so which ones do you use???