Friday, February 27, 2009

Transmission Lines for Dummies

T-lines for dummies ...

A 1/4-wave of anything* will match a 50-ohm antenna back to a 50-ohm radio....
73
Scott
KD5NJR

" Myth #4 - A quarter wave transformer can always be used to match the antenna to the transmission line.
Basic Truth #4 - A quarter wave transformer has no magical properties. It can be used between two impedances for which the characteristic impedance of the transformer is the geometric mean. For example, a quarter wave, 75 ohm line will match a 112 ohm antenna to a 50 ohm line. Great! However, if you are familiar with the Smith Chart or other techniques for designing matching sections, you can use lengths of transmission line, both open and shorted, to obtain transformations or to make impedance corrections. (See "Quarter Wave Transformers" below)"

* It will help, I think, if the velocity factor of the material is close to 1.

1 comment:

Gene (AE5FT) said...
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