From: entilleser@... So, presuming that I have a 450 ohm load at the end of the ladder line (which might not necessarily be true, under the circumstances), by connecting the VNA to the 1:9 balun, the VNA should report an impedance of 50 ohms, correct? ... For example, if the actual impedance at the end of the ladder line were 900 ohms, the VNA would report an impedance of 100 ohms.
Concerning ideal TLTs: First sentence above is true. Second sentence is false. A Transmission Line Transformer has an electrical length. If the load on the 9:1 TLT-balun is not the designed-for load of 450 ohms, the transformation will not be 9:1. A TLT is NOT an ordinary (N1/N2)^2 transformer. Another way of saying the same thing is: If the SWR on the 450 ohm ladder line connected to a 9:1 TLT is not 1:1, then the impedance transformation ratio will most probably not be 9:1. As an illustration, here is a graph of the impedance at the output of a 50 ohm 1:1 TLT vs the "transformed" impedance at the input of the 1:1 TLT. Note that the only point at which the transformation ration is close to 1:1 is when the impedance at the output is close to 50 ohms.
