given 100 watts of output from a fixed 50 ohm transmitter into a 50 ohm load, how can we confirm the output impedance of the transmitter? since Z = E / I, we measure the voltage and current present at the transmitter output. in the meantime we have already been given P and Z. now we derive I and E.
I = sqrt of P / Z
100W / 50Z = 2
sqrt/2 = 1.414A
given P, Z and I
E = I X Z
1.414A X 50Z = 70.7V
E = 70.7V and I = 1.414A. dividing the current into the voltage we get 50 ohms. i just measured the output impedance of the transmitter under non-reflective load conditions. you decide, is that the same thing as "reading" the impedance?
is the power output really 100W? 70.7V X 1.414A = 99.9698W.
is the current really 1.414A? 100W / 70.7V = 1.414A
is the voltage really 70.7 volts? 100W / 1.414A = 70.7V
is the impedance really 50Z? 70.7V / 1.414A = 50Z
there's no impedance without current and voltage
there's no SWR without impedance.
in this scenario, the only conditions under which the swr can possibly increase with an increase in power is when the combination of voltage and current deviates from a 50:1 ratio, caused by a change in the antenna load impedance, a change in the tuning and loading of the transmitter or a feedline (short or open) fault
actual measurements and calculations based on 100W CW, "brick on the key."
