Dave wrote:
better get out the snorkle... if you tie the braid and the center conductor
together you get a 25 ohm line, i use that all the time for my stack
matching boxes.

Nobody said anything about tying the braid and center conductor
together. If the side by side run of 50 ohm coax is used as a
parallel feedline, the braids are tied together and the Z0
is 100 ohms when the center conductors are connected across
the load.
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73, Cecil http://www.qsl.net/w5dxp