[PVRCNC] MFJ-259B inductance measurement

[Guy Olinger K2AV]

I quit trying a long time ago to make the MFJ 259x be a do-all when they
clearly had no intention of designing for that.

I bought the LC meter at http://www.aade.com/lcmeter.htm and have never
looked back. Trying to do good stuff with boxes not intended to the task is
a woeful time-killer. Buy the good test equipment. Skip some trips to
McDonalds and the movies.

It has always been handy to know what the ACTUAL capacitance was of
something labeled 650 pf +/- 20%. It helps to know that a pile of ten of
them are all very close to 580 pf.

A couple of fairly expensive HEC HT50 transmitting caps labeled 170 +/- 20%
are 158 and 159 pf, which is helpful when you are trying to cut a resonator
coil out of coil stock. Cuts in the wrong place waste money.

73, Guy.

On Sat, Sep 13, 2014 at 7:55 PM, Dan Atchison via PVRCNC <
pvrcnc at mailman.qth.net> wrote:

>  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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