KJ4UO wrote:
"If I have an RG-58 coax and it is shorted at the load end."

At the electrical input, 1/8-wave back from the short, you have an
inductive reactance equal to the numerical value of Zo. At 1/4-wave back
from the short, you have added an open-circuit 1/8-wavelength of line to
the first. This new line has a capacitive reactance equal to Zo.

The combination of equal and opposite reactances makes a parallel
resonant circuit equivalent which seems a very high impedance indeed.

Best regards, Richard Harrison, KB5WZI