Buck wrote:
ok, a 100 ohm load fed with 50 ohm coax is a 2:1 swr. Fed with 75 ohm
coax, it is 1.33:1 ??

Yes, and 75/1.33 = 56.25 ohms. For a perfect match to 50
ohms, one would need Z0 = SQRT(100*50) = 70.7 ohms.

If the 75 ohm is fed with 50 ohm coax 1/4 wave down the 75 ohm coax,
it will be a close match?

The SWR on the 50 ohm coax will be 56.25/50 = 1.125:1

Why did the impedance change to 52 ohms?

It didn't. It changed to 56.25 ohms. The load is 100 ohms
and the Z0 is 75 ohms so the SWR is 1.33:1 at the current
minimum/voltage maximum point. To find the impedance 1/4WL
away, divide Z0 by SWR, 75/1.33 = 56.25 ohms.
--
73, Cecil http://www.qsl.net/w5dxp