[PVRCNC] MFJ-259B inductance measurement

[Dan Atchison via PVRCNC]

 Put a known capacitance across it and measure resonance. See if the formula works backwards to the inductance value. 


>
>
>Saturday, September 13, 2014, 7:02 PM -0400 from Mike Barts  <mike at bentwire.net>:
>I'm building some loading coils for my 40m beam. I designed the coils
>using several of the online calculators as sanity checks. The final
>design is built using 1/4" copper tubing, 5" air coil supported by
>two 3/4" strips of Delrin. The design inductance is 2.64 uH. When
>measured by my MFJ-259B in inductance mode, it's measuring a little
>over 4 uH. I've got the inductor suspended by a string, hanging in
>the air in the garage to minimize coupling. Anything metallic (except
>the -259B case) is at least a foot or two away. The lead lengths to
>the MFJ-259B are about 6" long.
>
>Are there any known issues with inductance measurements with the
>-259B? (yes, other than it being an MFJ product....) While I didn't
>expect an on the money inductance, 4 vs 2.6 is a big error. Don't
>think the lead lengths are THAT long to add almost 2 uH, and I don't
>think my inductor design is THAT far off.. Looking to see if I'm
>missing something obvious or there are issues I'm not cognizant of.
>All suggestions, other than trashing the -259B, welcome.
>
>73, Mike N4GU
>
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