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 <[email protected]>
To: Jay Rusgrove <[email protected]>; <[email protected]>
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.
>
>
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