Several of you gave me advice last month regarding how to determine
coefficient of coupling for the air-wound inductors in my link-coupled
antenna tuner.
Wanted to let you know how it turned out.
I used a computer program called Inca to calculate a coefficient of
coupling of 0.51 based on the physical dimensions of the coils and their
positional relationship.
Recently I was able to use a Sencore LC-102 capacitor-inductor analyzer
on the set of coils. The coefficient of coupling is 0.52 based on
measured values individual coil inductances and aiding/opposing mutual
inductances.
Pretty close correlation between the two methods of determining the
coefficient of coupling and more than adequate for my needs.
Again, thanks to all for the helpful advice.
Steve K8JQ
-------- Original Message --------
Subject: Re: [TowerTalk] Coefficient of coupling
Date: Sun, 25 Sep 2005 12:31:52 -0400
From: Steve <steveac@charter.net>
To: richard@karlquist.com
CC: towertalk@contesting.com
References: <43360959.50407@charter.net>
<12472.66.81.100.92.1127664133.squirrel@webmail.sonic.net>
Hi Rick,
Thanks for the info, I thought the methodology existed but didn't
immediately find it. Appreciate the offer to scan and send but I don't
think it will be necessary.
Jim Lux, in an off-reflector note, steered me to a program named Inca at
http://www.coe.ufrj.br/~acmq/programs/. It appears that this will meet
my needs.
I'm working on a link-coupled antenna tuner for 160 meters and was
curious about the coefficient of coupling for the inductive link. Inca
indicates the coefficient for my pair of coils is 0.51.
Thanks again and 73,
Steve K8JQ
Rick Karlquist wrote:
> Steve wrote:
>
>>Just wondering if there's a way to determine coefficient of coupling
>>based on the physical dimensions of the two coils and their mounting
>>with respect to each other?
>
>
> Of course, F. W. Grover figured this out a century ago.
>
> Grover, "Formulas and tables for the calculation
> of mutual and self inductance", NBS Paper 169, 1912.
> (NBS is now NIST)
>
> Grover, "Tables for the Calculation of the
> mutual inductance of any two coaxial single
> layer coils", Proceedings of the IRE,
> July 1933 pp 1039-1049. (IRE is now IEEE).
> This paper claims to have easier to calculate
> formulas. Of course that was precomputer. Not
> clear which would be easier now.
>
> I have the latter paper in my personal library. I can
> scan it in if you can't find it at your local engineering college.
> I also have the NBS book, but it is fairly lengthy to scan in.
>
>
>>Didn't find it in the Handbook, nor did a google search turn up anything.
>
>
> Google on "grover" and "inductance" and you'll get a bunch of hits.
>
>>Steve K8JQ
>
>
> I can tell you ahead of time that it is difficult to get coupling
> above 50% and impossible above 80% or so.
>
> Rick N6RK
>
>
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