I ran across some statements in a magazine artical a while back that has me
wondering if true or not.

One example is that a directional wattmeter such as the Bird does not make
any differance as to the line impedance. That is if you have a 50 ohm line
and 50 ohm antenna or a 70 ohm line and antenna, the swr will calculate to
the same which in this case would be 1:1. Also if the line and load
impedance is differant, the swr will still calculate out to the same. that
is say you have a 50 ohm line and 100 ohm load or a 70 ohm line and 140 ohm
load the same directional wattmeter such as the Bird or a Drake w4 will
still calculate the same 2:1 swr even if they are not set up for the
differances in impedance. All that is asuming a line say 50 to 100 feet
long so the standing waves can really form.

I do know that the transmitter tuning will be differant due to the 50 or 70
ohm impedance even if the swr shows 1:1.