[R-390] IF Trimmer notes

[Barry]

Well, with *some* air variables.  The type that have a mechanical stop at
maximum capacitance will only have one "true" peak or null (depending on the
circuit).

Barry - N4BUQ

----- Original Message ----- 
From: "Roy Morgan" <roy.morgan at nist.gov>
To: "Barry" <N4BUQ at aol.com>; "Cecil Acuff" <chacuff at cableone.net>;
"R390list" <r-390 at mailman.qth.net>
Sent: Wednesday, February 01, 2006 8:56 AM
Subject: Re: [R-390] IF Trimmer notes


> At 09:10 PM 1/31/2006, Barry wrote:
> >Cecil,
> >
> >Good analysis.  I'd assume that with any of the ceramic trimmer types, if
> >you don't get two peaks (or nulls as the case may be), the cap isn't of
> >sufficient value due to whatever due to the mechanical nature of their
> >construction.
>
>
> Barry and all,
>
> It goes like this:
>
> As the trimmer is rotated toward it's minimum value, the circuit begins to
> resonate but needs less capacitance than the minimum. Thus you get only
one
> dip, but the dip is not at resonance.
>
> OR:
>
> As the trimmer is rotated toward it's MAXimum value, the circuit begins to
> resonate but needs more capacitance than the MAXimum. Thus you get only
one
> dip, but the dip is not at resonance.
>
> If the real resonance point is within the range of the trimmer, you'll get
> two dips, one on either side of maximum capacitance.
>
> The same applies to air variables.   With slug tuned circuits, or with
> compression trimmers, you get more of a hint of what's going on because of
> the position of the shaft or screw.
>
> Roy
>
>
> - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> 7130 Panorama Drive, Derwood MD 20855
> Home: 301-330-8828 Cell 301-928-7794
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> roy.morgan at nist.gov --
>
>