Walter, W2DU wrote:
"The magnitude rho of the reflection coefficient was obtained from SWR
measurement using the equation rho = (SWR-1)/(SWR+1), thus the PRD
actually measured the compleete complex reflection coefficient."

Walter is on solid ground. Slotted or trough lines have been around for
a long time. The formula Walter used to calculate a reflection
coefficient rho is given by Terman as eqn. 4-22b on page 97 of his 1955
opus.

Best regards, Richard Harrison, KB5WZI