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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <001101c69f68$fa306a90$6501a8c0@eagles> <001801c69f70$bef1a9a0$0300a8c0@lark> <000901c69f77$db074850$6501a8c0@eagles> <002b01c69f7e$701bbec0$6401a8c0@JAYTERMINAL> <004701c69ff7$2298b710$6501a8c0@eagles>
Date: Wed, 5 Jul 2006 09:24:17 +0100
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Subject: LF: Re: Antenna Tuning
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Dear JA, LF Group

Using your variometer's winding data, and Claudio's calculator, the
adjustment range comes out to 2.8 - 6.6mH. This seemed very large, but
calculating the two coils as isolated solenoids and adding their inductance
gives the correct "mid-range" inductance, so it is definitely a realistic
estimate. So the first problem is that the variometer is just too big!

The obvious solution would be to reduce the number of turns by a factor of
about 2 - but before getting this drastic , I calculate that since:

outer coil = 3.38mH
inner coil = 1.33mH
mutual inductance (added to both coils) = +/-0.95mH

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

----- Original Message -----
From: J. Allen <vy1ja@northwestel.net>
To: Jay Rusgrove <JRusgrove@comcast.net>; <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, July 05, 2006 6:52 AM
Subject: LF: Antenna Tuning


> Jay, Scott, Steve and All,
>
> Thanks for the note.
>
> The Variometer is built with two coils in both the stationary and rotory
> windings.
> Each of these have a one inch space between the coils to allow for the
> rotating shaft.
>
> The stationary coils are wound on a 10-3/4 inch former at 19 or 20 TPI
> closewound
> with about #16 solid electric motor wire.  The two coils are each 3-1/8
inch
> long.
> The bottom coil has a number of taps.
>
> The rotary coil is 7-1/2 inches long and 6 inches in diameter close wound
> with the
> same wire.  Subtracting 1 inch gives 6-1/2 inches and makes the two coils
> total
> 3-1/4 inches length each.  This is as close as I could match the inner
coils
> to the
> outer ones.
>
> If someone knows how to estimate how much inductance range this variometer
> is likely to have I would appreciate knowing.
>
> I have built a ScopeMatch which works well with the dual trace scope which
> Scott, VE7TIL, leant me.
>
>