On 2/14/2013 5:33 AM, Jim Lux wrote:
I think the OP was looking for a impedance transformer, and for that
application, I think small errors in length won't have a big effect.
Say you were using 1/4 wavelength of 75 ohm line to transform 50 ohms
to 112.5 ohms.. If the line were 7/32 wavelength, would it be that
much different?
You're right, it would not, but the effect is not zero. AND -- the
resonance that a length of line like this provides can do some VERY
interesting and useful things in broadbanding resonant antennas. That
piece of line is a quarter wave at the design frequency, but on one side
of the design frequency it's inductive, and on the other side it's
capacitive. Depending on the antenna and the rest of the system, the
error could help or hurt.
One can learn a lot by building a simple NEC model of a dipole,
exporting it to SimSmith, and seeing what happens with various lengths
of line of various impedances.
73, Jim K9YC
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