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| Actually I measure my VHF and UHF yagi elements in mm. And they perform well at CSVHF antenna measuring events.
The meter was based on being 1 ten millionth of the distance from the equator to the north pole. As surveying got better and the fact that the earth is not a perfect sphere was discovered, the standard meter is not exactly that dimension. For a long time it was the distance between two lines scratched in a metal bar kept at a controlled temperature in Paris. Now its based on wavelengths of monochromatic light from a certain gas.
The original foot was a British monarch's foot, but now its based on being 12 inches each inch being 2.5400000 centimeters. and so on the same wavelengths of light in Paris.
Most of my tapes and measuring sticks have both metric and fractional marks and after 60 years of working in mixed units (been a ham for 59 of those years) I can make lots of common conversions from fractions to mm or back or compare them without thinking at all. Like 19mm is 3/4". 1/2" is 6.35 mm, 50 mm is 2 inches. Close enough for lots of fabrication where one needs to drill holes a little oversize to allow for inaccurate positioning. I keep calculators on all my benches and remember that 1mm is 0.03937 inches and that takes care of the odd conversions.
Gerald J. | |
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Reasons to use metric
