If that interfering nuisance of your fold-back
circuit springs into action then it means the pure input resistance is
something other than 50 ohms.

Hi Reg,
That foldback circuit is an interfering nuisance agreed, but it comes in
handy at times. My homebrew mobile antenna is difficult to keep tuned, much
less in one piece doing 100 km/hr down the US Interstate system. My HF
transceiver folds back if things are not right with the antenna system.
The fold back circuits tell me I need to do something with the mobile
antenna, before I smoke the final semiconductors in my rig. It doesn't tell me
what I need to do, I use other stuff for that. I used a couple of your
programs in the design of this beast, Thanks!
73 Gary N4AST