Hey Carl,we all know how to get things close with the formulas....Some folks
just like to hammer things to death...Practical building/tuning experiance
rules because every brewed amp is diffrent...I think if I remember correctly
a fellow that used to post here nearly every day,turned nearly everyones
comments around to his point of view.(No name)..If you responded to him off
list,be prepared to exchange emails back&forth at least until he got the
last word in..I told him one time and I quote:If you can`t dazzle us with
your brilliance,you`ll baffle us with your BS....I like this group now,we
have some very devoted builders and a few excellent engineers with time to
answer questions of interest to us all...My thanks to all of you,73,Jim..
----- Original Message -----
From: "c." <carlseye@tampabay.rr.com>
To: "Tom W8JI" <w8ji@w8ji.com>
Cc: <amps@contesting.com>; <garyschafer@comcast.net>
Sent: Monday, April 16, 2007 2:49 PM
Subject: Re: [Amps] Tank circuit Q
> 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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> >
> >
> >
>
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