ORIGINAL MESSAGE: (may be snipped)
On Tue, 28 May 2013 07:56:27 -0700 (PDT), you wrote:
>Now that you have the setup, here's the question: "For a given
>frequency, if your circuit tunes with more capacitance (Tune)
>in one position but also tunes in another position with more
>turns on the tank coil but less Cap on the Tune side, what could
> be said about the coil, the, Q and which position for that
> "Given Frequency" would be best to tune at"?
REPLY:
There is an infinite combination of tune C and L for any given frequency.
Basically you are asking "what is the best Q for a tank circuit?".
As with many things, there is no single "best". What works is a Q of between
10 and 15 or so. Lower Q is more efficient and more broadly tuned but has
higher harmonic content. Higher Q is just the reverse.
I would suggest aiming for a Q of about 12 and don't worry if it turns out
to be 11 or 13. The difference is not worth worrying about. Excessively high
Q can be a problem on the higher frequencies because of stray capacitance.
If the Q works out to be no more than about 20 or so, you can choose to just
live with it. More than that and there is a neat trick to get it down
involving a simple L-network. Any ARRL handbook for the last few years will
have details in the amplifiers section.
If you don't have one already, you should a spreadsheet like GM3SEK's to do
the calculations for you. You can google for it.
73, Bill W6WRT
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