Reg Edwards wrote:
Reg Edwards wrote:
Ferrites have as many vices as they have virtues.

Ferrite salesmen cleverly make virtues out of vices.
================================================
But an electronics 'homebrewer' can find out characteristics anyway
,
through experimentation.

Frank GM0CSZ / KN6WH
====================================

Only if he has first-class laboratory facilities.

And samples vary widely in their characteristics, one from another.

The best way of using one is to wind some wire on it. If it works in
your particular circuit then consider yourself lucky.

It's not nearly as bad as Reg says, and a surprising response from
someone who measures ground conductivity to great depths in a kitchen sink.

An antenna analyzer hardly qualifies as "first-class laboratory
facilities", yet it can quickly show you the impedance and Q of an
inductor wound on a core at any frequency within its range. If
saturation with DC is a problem, the impedance can be measured while DC
is passed through another winding from a source having a high impedance
at RF. And samples of cores are typically alike in basic characteristics
within a few percent.

Ferrites are more commonly used at RF for wideband transformers and EMI
suppression than for high-Q inductors. In those applications, minimum
impedance magnitude is usually the criterion rather than Q or having a
precise value. So even a rough approximation of impedance is usually all
that's required. The magnitude of impedance can be measured with a
variety of simple means in addition to an antenna analyzer. Only in
those applications where a high Q inductor is required, usually at low
frequencies, are better measurements required.

Roy Lewallen, W7EL