Re: NEC-LIST: Coil Q

I am now convinced that my inductor Q calculations have been way off. I
am investigating this and have been drawing diagrams of the magnetic
field at each wire to get an idea about proximity effect and how it will
crowd the current into a small area of a conductor. When I get some more
information I will post it here. Does anyone here have a good way to
calculate coil Q?

   Dave Cuthbert

-----Original Message-----
From: nec-list-bounces+drcuthbert=micron.com_at_robomod.net
[mailto:nec-list-bounces+drcuthbert=micron.com_at_robomod.net] On Behalf Of
Greg Durnan
Sent: Tuesday, February 08, 2005 8:23 AM
To: nec-list_at_robomod.net
Subject: NEC-LIST: Coil Q

Hello,

I've been building radio coils for the last year for nmr instruments.
I construct them for use between say 40 and 400MHz and use copper or
silver plated wire ( generally about 40 to 400nH - perhaps 1 to 10
turns on up to a 10mm air core). Q's generally range between 50 and
200 ( a particularly good one) when coils are used in conjunction with
good ATC ceramic caps. I have seen slightly higher Q's perhaps ( maybe
mid 350's) on occasion, but I would be reluctant to offer any
guarantees on those types of numbers. Testing has generally been done
on a by using the curve fit on a VNA notch measurement... perhaps not
the best way.

G.J.Durnan

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