[PVRCNC] MFJ-259B inductance measurement

[Dan Atchison via PVRCNC]

 I have one if those meters if you care to borrow. 


>
>
>Saturday, September 13, 2014, 8:12 PM -0400 from Guy Olinger K2AV  <k2av.guy at gmail.com>:
>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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