Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org)
From: "james moritz" <j.r.moritz@herts.ac.uk>
To: <rsgb_lf_group@blacksheep.org>
Date: Wed, 5 Jul 2006 14:58:44 +0100
Message-ID: <000001c6a03b$2171ab50$e6a4c593@RD40002>
MIME-Version: 1.0
Importance: Normal
In-Reply-To: <002501c6a00c$68dcf280$2e5e7ad5@w4o8m9>
Subject: LF: RE: Re: Antenna Tuning
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

Dear JA, LF group,

The basic idea of connecting the variometer coils in parallel seems to =
be
sound, but I made an error in the calculation. More careful calculation
shows that, for the parallel connection:

L =3D (L1L2 - M^2)/(L1+L2-2M),=20

Where L1, L2 are the inductances of the two coils individually and M is =
the
mutual inductance between them. In this case, L1 =3D 3.38mH, L2 =3D =
1.33mH, M is
between -0.95mH and +0.95mH, making the adjustment range for JA's =
variometer
with the coils in parallel 0.54mH - 1.28mH, which is still OK. =
Calculating
inductances of coils is often not very precise, so it would certainly be =
a
good idea to check the inductance as Peter describes, to make sure you =
are
in the right range.

Cheers, Jim Moritz
73 de M0BMU

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of James Moritz
Sent: 05 July 2006 09:24
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: Antenna Tuning

Dear JA, LF Group

...

Connecting outer and inner coils in parallel instead of in series will =
give
an inductance range of 0.32 - 1.49mH, which would be good. I am not =
quite
sure if this is correct, so will have to check.

Cheers, Jim Moritz
73 de M0BMU