Re: NEC-LIST: Coil-loading.

I have always assumed that an air-core toroid coil would be superior to an
air-core solenoid - it should have a more compact magnetic field and
increased inductance for a given wire resistance. That should make it
higher Q, right?

But air-core toroids never became popular, or at least I have never seen
one in manufactured equipment. If I am right about the more desirable
electrical characteristics, why didn't we use this form even before modern
core materials were developed?

Jerry W4UK

At 02:33 2/8/2005, J. C. Mc Laughlin wrote:
>One can not tell if sending a message will work as the Canadian server does
>not like my (no-choice) headers, but here goes:
>
> Years ago, I had access to two different Q-meters and the best quality
>impedance measuring equipment. As an exploration of the issue of
>attainable, unloaded inductor Q, I built and tested a number of coils over
>about a two day period
>
> I could approach a Q of 300. I am able to believe that with further
>thought and experimentation one might reach the neighborhood of 450. I
>blanch at 1000.
>
> The coils I am contemplating are air-core, solenoids using copper wire
>(at about 24 C). The self resonant frequencies (parallel) of the inductors
>were between about 5 and 10 MHz.
>
> I am keen to learn how to make a passive, air-core inductor with a Q
>approaching 1000.
>
> James C. Mc Laughlin
>9:33 PM EST 7 Feb 2005
>
>J. Mc Laughlin; Michigan U.S.A.
>Home: JCM_at_Power-Net.Net
>
><drcuthbert_at_micron.com> writes:
> > Doug,
> >
> > A Q of 300 can be achieved with close spacing of the windings on a
> > dielectric rod. A Q of nearly 1000 can be achieved with a properly
> > designed air-core solenoid inductor.
> >
> > Dave Cuthbert
> > Micron Technology
> >
> > -----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
> > D. B. Miron
> > Sent: Monday, February 07, 2005 8:35 AM
> > To: nec-list_at_robomod.net
> > Subject: Re: NEC-LIST: Coil-loading.
> >
> > Good day,
> >
> > Jim is right about the original question. I have a 1943
> > copy of Terman and I don't see anything about coil loading.
> > He has a very brief paragraph on automobile antennas in
> > which he mentions the whip, and plate antennas.
> >
> > A related question is about coil Q. I read somewhere that
> > the maximum practical Q or an air-core solenoid is about
> > 300. Does anyone disagree, or have different experience?
> > Thanks.
> >
> > Doug Miron

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