Richard Clark wrote:
"Has anyone here actually measured SWR without using a diode?"

I did something similar and could have used the same rig to measure SWR
in a feedline.

I used a wire loop which included a thermoammeter suspended from a
horizontal antenna element. I pulled this along the element to measure
its current distribution using a long tow rope and a telescope.

Pulled along a transmission line wire, this would have produced the
currents at the minima and maxima along the wire. From these we could
calculate SWR.

Best regards, Richard Harrison, KB5WZI