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Re: [TowerTalk] MF-259B

To: <>
Subject: Re: [TowerTalk] MF-259B
From: Andy <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Tue, 16 Mar 2010 09:15:41 -0400
List-post: <">>
> When measuring inductance with the MFJ you need to use the lowest
> that will give a reading. Same when measuring capacitance.
> It is sort of intuitive to set it to the frequency that you are making the
> coil for but that introduces too many errors, stray capacitance,
> etc.

There's some truth to that, but one also might argue with it.

IMO, there is benefit in knowing BOTH the low frequency inductance or
capacitance, and the value at the frequency of interest.  The former is the
asymptotic value, the one without stray parasitic capacitance or inductance.
But the latter may be the one you really want to know, especially if those
parasitics are in the coil or capacitor being tested, and therefore
important to the operation of the component at your normal operating

It does you no good to know that a coil has 5uH of inductance at audio
frequencies, when it is really something very different at RF frequencies.
The coil will have some self capacitance, they all do (it eventually leads
to self resonance), and it changes its effective RF inductance, and that is
very much important to the proper operation of that coil at that RF

Just be aware that the '259B itself has some terminal capacitance of its own
which might corrupt your measurements at higher frequencies, and all device
leads have inductance.  Know when what you are measuring, is in the part, or
in the test instrument.  Don't ignore it when it is part of the coil you are

> ## it's a dead loss  when measuring inductance and Capacitance.  I Tried
using it to make tank coils for
> hb linears, and it's out to lunch, not even close.  3 x mfj's  were tried.

Perhaps the problem was how you used it.  It is not a "dead loss".



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