> "Adding a matching circuit at the transmitter (tuner) or adjusting the
> length of the feedline such that a 50 ohm resistive impedence is presented
> to the source does not change the VSWR in the feedline. Yes, the VSWR
> between the source and the tuner will be 1:1, but the VSWR in the feedline
> will remain unchanged."
Sometimes VSWR does change significantly along a line -- and not always for
reasons of loss nor common-mode RF current on the outside of a coaxial line.
Consider this example:
At the operating frequency, a dipole at its input terminals is exactly 50
ohms resistive (50+j0). Let's feed the dipole with an electrical half-wave
of low-loss 600-ohm open line. VSWR on the line is 12:1. Correct?
Finally, let's connect a random length of 50 ohm, low-loss coax to the input
of the 600 ohm line.
What is the VSWR on the 50 ohm section of line?
A. Is it still about 12:1 because VSWR does not change on a low-loss line.
B. Not enough information because you didn't state the coax length.
C It's now about 6:1
D. It is now 1:1
E. You can't terminate a coaxial line into a 600-ohm balanced line without a
current balun and get an answer.
F. None of the above.
Bonus question: What is the impedance at the input to the 600-ohm line
So, here we have one transmission line composed of two types. Ignoring
loss, is the VSWR really the same at all points on the transmission line?
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