Re: New ideas for improvement from SQ9PXD

Yury Kuchura EU1KY

Hi Wolfgang,

One more interesting feature has been added to my version (H745 code, and EU1KY branch of the F746 code): open line Z0 measurement.

The algorithm is simple: it finds the frequency of the line's first L/4 resonance (where X becomes 0 while R is very low), and measures impedance at the half that frequency, where line phase length of that line is L/8. The X value on L/8 frequency is a very well estimated line Z0.

But take into account that in a real life a line Z0 is a complex value for each particular frequency, caused by imbalance in dielectric and electric losses in the line. For example, a high-Z ladder line made of a very thin wire has almost perfect dielectric but a poor conductivity, its Z0 is very complex and varies with frequency. The same is for AC facility wire with a thick PVC dielectric which performs extremely poorly on RF, but the copper wire inside is thick and good. So Z0 value can only be estimated with this algorithm, though, this estimation is very good for properly designed low-loss lines. Anyway, this feature is extremely useful for building wideband HF transmission-line transformers.

73! EU1KY

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