[PVRCNC] MFJ-259B inductance measurement

[Bert via PVRCNC]

IMHO, you may use what you have for  instrumentation, provided you know 
what it's telling you. It may be  cheaper/easier to get a "standard" (or 
several, for that matter) and either  re-calibrate your MFJ-259B or at least know 
the "offset" (and determine if it's  linear!). If it's non-linear or screwy, 
no matter what, then find another  measurement source.
You could use Guy's capacitance meter and get a reference  capacitance for 
use in measuring resonance; the MFJ should do pretty well in  that respect, 
and you can check the MFJ's calibration using your own  receiver.
73,
Bert (still in Maine!)

In a message dated 9/13/2014  7:03:04 P.M. Eastern Daylight Time, 
mike at bentwire.net writes:
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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