Albert -

Electrolytic caps are really not very good in resonant circuits.

First, you must not allow the cap voltage to go negative - which means
you must ensure that there is a DC bias at least as great as the peak
voltage of the sine wave that will exist there.

In addiion, they have a fair amount of series resistance (which will
drag down the Q of the overall circuit). And because of their
construction, they also have a fair amount of parasitic inductance -
probably well above 10 uH. Just as a general statement, at KHz
frequencies, you probably should be thinking about mH coils and nF caps.

Bill
--------------------

Albert wrote:
No, that is not an error. I meant 8.2 uf, not 8.2 uuf.

The 10 uh coil is easier to make, so I wanted to use a small inductor
and a large capacitor. It should resonate at 17.8 Khz, which is the
frequency I am building a receiver for.

Why does everyone think this is a joke and/or an error? This is a
legitimate question. I gave (what I thought) was the specifications
needed to arrive at a value for loaded Q....or at least a rough
estimate.

Thanks to all,

A



On Sat, 02 Apr 2005 06:45:54 -0000,
(Stan) wrote:


Albert wrote:

}I need to have an estimate of the Q for a parallel tuned circuit
}consisting of a 10 microhenry air wound coil and an 8.2 microfarad
}electrolytic cap.

An "8.2 microfarad" cap in an RF tuned circuit?

Please re-check...perhaps you meant 8 uuf?

Stan.