In article , Paul Burridge
writes:

On 22 Mar 2004 01:46:20 GMT, (Avery Fineman)
wrote:

[snip]

Phew! Thanks, Len. There's rather more to these ''simple inductors"
than meets the eye, it seems.

Yes, but it probably took longer to write the procedure out than
to actually do it. :-)

As a _starting_ procedure, work with magnitudes of impedance,
or the square-root of the sums of the squares of resistance and
reactance. That's easy enough on a conventional "four-function"
pocket calculator that has the added square-root function.

For a single resonant circuit you should be interested in the ratio
of magnitude at desired frequency to the magnitudes at the
undesired frequency. The bigger the ratio, the better selectivity.

If you want to investigate toroidal coils (for their smaller size), you
can find Q curves at - http://www.amidoncorp.com. Those look
exactly like the Q curves in my Micrometals Q Curve subsection
of their (surface mail only) catalog. Under one of the links at the
top right you will get a rather long html page with over a dozen
curves on it representing over a half dozen typical inductors per
graph over a wide frequency range. Save that page if you can,
it is good for reference later.

www.micrometals.com seems to be down on Monday, probably
for website revision; haven't heard any rumors that Micrometals
went out of business. Micrometals has foreign (to the USA)
distributors and sales reps so I was hoping to show some of
those in or near the UK.

For cylindrical coil shapes, Reg Edwards program is about as
good as it gets to save wear and tear on pencil and paper.

Len Anderson
retired (from regular hours) electronic engineer person.