Smith did not invent the Smith Chart. He simplified, for HF use only,
charts which had been in existence since the Victorian Age, which
covered all transmission line frequenies down to telephone and power
frequencies.

You should be warned against using Smith Charts at frequencies less
than about 1.5 or 2 MHz. Errors can be introduced of which you may be
unaware.

On the other hand, at higher frequencies, the Smith Chart is an
accurate time saver when making ordinary engineering transmission line
calculations.

But now very much superceded by small computer programs which exceed
the Smith Chart in both user time and accuracy,
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Reg.