[Amps] Tank circuit Q

[c.]

   I have not replied to these threads because I do not consider myself 
to be the "utmost"
     expert on any of the questions.!!  However, insofar as "Q " is 
concerned, I have always thought of it as "how sharp, or how broad " is 
the tuning .!!   from this point, I have had very good results on almost 
any tuned circuit, whether transmitting or receiving.!!
   I*t's just a matter of perspective, and maybe many years of 
experience, I guess.!!
    If I step on any toes, well , I'm sorry.!! And I know of course that 
the younger folks may not understand, but that's the way I learned these 
things.(long before I knew any of the
 Formulas)  (if any existed )
      carl / kz5ca



Tom W8JI wrote:
> I think what confuses people is that commonly used amateur 
> radio formulas for tank Q are really just rough shortcuts or 
> approximations for describing real world systems. The saving 
> grace is the system, unless Q is below a minimum value, 
> doesn't change nearly as much as many might think when 
> operating Q is not the magical numbers (like the popular "Q 
> must be 12") that we are so overly fond of zeroing in on.
>
> The formulas are all approximations and should not be taken 
> as a description of what precisely happens in the network or 
> in the real world.
>
> I wouldn't spend too much time worrying about making an 
> approximation fit a non-critical goal precisely!
>
> The capacitor current, assuming a sine wave from a purely 
> resistive source driving the tank, would be simply the RMS 
> voltage at the tank input over the capacitor's impedance. 
> This is true regardless of inductor unloaded Q.  Current in 
> the inductor is slightly different  than that in the real 
> world because there are other shunt impedances at work in 
> the system, and the waveform is not a pure sinewave. But it 
> is close enough.
>
> As for capacitor current, be sure to read the manufacturer's 
> detailed application guidelines carefully. There are many 
> people who apply a base number that is designed to be used 
> in a series of approximations directly as a limit, and who 
> wrongly assume any current beyond the number that was never 
> intended to be an absolute limit results in some component 
> life or operating catastrophy.
>
> The two parallel capacitors in series with your tank 
> variable C clearly need to go. They are a sign of bad 
> engineering, just as the shorted taps on the toroid were.
>
> 73 Tom 
>
>
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