"Dr. Slick" wrote in message
m...
Cecil Moore wrote in message
...
Dr. Slick wrote:
If you agree that the Pref/Pfwd ratio cannot be greater than 1
for a passive network, then neither can the [Vref/Vfwd]= rho be
greater
than 1 either.

Sqrt(Pref/Pfwd) cannot be greater than one. (Z2-Z1)/(Z2+Z1) can be
greater than one. Both are defined as 'rho' but they are not
always equal. (Z2-Z1)/(Z2+Z1) is a physical reflection coefficient.
Sqrt(Pref/Pfwd) is an image reflection coefficient.


I agree that Sqrt(Pref/Pfwd) cannot be greater than one for a
passive network.

(Z2-Z1)/(Z2+Z1) can be greater than one, for passive networks
and certain combinations of complex Z1 and Z2. I feel this is incorrect
usage of this formula, which should be limited to purely real Zo.
A [rho] that is greater than one gives meaningless negative SWR
data, and is limited to active devices.

it only gives negative swr values if you incorrectly use the lossless line
approximation to calculate vswr from rho. that is the incorrectly applied
formula in this case. that formula is not valid for a lossy line, you must
go back to the original definition of VSWR=|Vmax|/|Vmin|. which as we have
also noted is not meaningful on a lossy line as Vmax and Vmin are different
at each max and min point because of the losses in the line affecting both
the forward and reverse waves.