----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Tuesday, June 11, 2002 10:39 AM
Subject: Re: LF: DJ
Dear Mal, LF Group,
At 19:59 10/06/2002 +0100, you wrote:
>. Two taps on the coil permits freq adjustment from 135.7 - 137.8 khz...
Something is wrong if you need to adjust the tuning within this range -
the
output should be flat within a fraction of a dB over the whole band
without re-tuning.
Nothing wrong, I am fussy and like everything on the nose, and not bits of
dangling wire on the top of coils that you can wind one way or the other to
fudge an approximate resonance.
Perfection is my aim.
Incidentally, an inductor that works OK for a low pass filter won't
necessarily be suitable in this type of tank circuit - in the low pass,
the
loaded Q of the circuit is usually 1 or less, depending on design, while
in
the tank circuit it is about 6. This means the tank circuit inductor has
to cope with reactive power several times greater than the low-pass
inductor for the same power throughput - so beware!
Mine runs ICE COLD. Surprised you have not tried this approach Jim instead
of using those big coils!!!!! and all that resistance !!!
G3KEV
Cheers, Jim Moritz
73 de M0BMU
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