----- Original Message -----
From: "Bill Fuqua" <wlfuqu00@uky.edu>
To: "Tom Rauch" <w8ji@contesting.com>; "2" <2@vc.net>; " AMPS"
<amps@contesting.com>
Sent: Monday, March 03, 2003 11:11 AM
Subject: Re: [Amps] Toroidal Tank Coils
> The phase relationship between voltage across and the current thru a true
> inductor is always
> 90 degrees. It may be less due to series resistance in the inductor but in
> an High Q inductor it should
> be very close to 90 degrees.
>
> Phase angle depends on your reference. It always takes two signals to
> establish phase.
> And in your case one is the anode and not the voltage across the inductor
> itself.
>
> Perhaps this will help clear some of the confusion.
>
> 73
> Bill wa4lav
>
>
> At 10:41 AM 3/3/2003 -0500, Tom Rauch wrote:
> > > Mr. Rauch -- 80% of 4000V = 3200V. 90% of 4000V = 3600V. What's the
> > > problem with 3500V?.
> >
> >Your normal diversion is to lift things out of context. The rest of my
> >answer explains the difference.
> >
> > > >which would translate to 3kV or more across the tank inductance.
> > > >The exact value depends on tank loaded Q, which sets phase shift
across
> >the
> > > >inductance. Q's of 10-12 result in about 130-degree shift,
> > >
> > > And I thought the phase shift in an inductor was 90?.
> >
> >You thought wrong.
> >
> >Phase shift depends on reactance and circuit impedances. A series
inductor
> >only causes a 90-degree shift when the load impedance is zero and the
> >inductor is infinite in value.
> >
> >In a pi-network tank system we have shunt capacitive reactances at each
end,
> >and a series inductance. The ratio of those reactances and the
termination
> >impedance of the network determines the phase shift. It is 90-degrees in
a
> >minimum Q network that matches two impedances, because the network
behaves
> >like a 1/4 wl transmission line with a surge impedance equal to the
> >geometric mean of the load and source impedances. The same formula that
> >would apply to a 1/4 wl transmission line applies to the CLC or LCL
system.
> >
> >In a pi, that is behaving like a pi, the network is two back-to-back L's.
> >This allows us to set phase delay over a wide range when matching two
> >impedances. There is no difference in talking about phase shift or Q.
Either
> >one can be translated into the other.
> >
> >This is why some engineers baffle people by speaking about phase shift in
> >tanks. They are really describing Q.
> >
> >Thank goodness things work the way they do, and not the way you thought
> >Rich! We would be in big trouble designing tank circuits and variable
phase
> >shift networks!!
> >
> > > >http://www.w8ji.com/demonstation.htm
> > >
> > > "In a 3000V PA stage, this would be 10,000V peak! It should make sense
> > > that amplifiers arc from grossly excessive drive power." -- Tom Rauch.
> > >
> > > - ... but it doesn't. In a worst case test with a SB-220 (a 3000V
> > > stage), the max peak V across the Tune-C was 3500V - which is c. 100V
> > > from flashing over. The idea of overdrive producing triple V does
not
> > > make sense since 3-500Zs are emission limited.
> >
> >Once again you totally miss a very important point.
> >
> >The capacitor and other components limit the peak voltage, not the tube
> >emission. A tank is an energy storage system. Unless something removes
> >energy at a rate faster than which it is applied, the voltage and
currents
> >will increase.
> >
> >Even a very small low-emission tube could build up extreme voltages if
> >nothing is draining off the stored energy faster at a higher rate than
> >energy it is being added.
> >
> > > >You'd better insulate appropriately for worse-case conditions, which
is
> >the
> > > >maximum breakdown voltage of the tank tuning capacitor times at least
two
> >or
> > > >three or whatever other component limits the peak voltage under a
fault
> > > >condiution.
> > >
> > > Kenwood used a 6000V Tune C in the TL-922 and the Tune-C does not
protect
> > > the 5000V bandswitch from arc-over. Kenwood apparently sells a heap
of
> > > 922 bandswitches.
> >
> >Yes, and the reason is explained in my web site. Your idea that emission
> >limits voltage is wrong. It is breakdown of some component, causing that
> >component to consume the excess energy, that eventually limits stored
energy
> >in a tank. Either that or the system reaches equalibrium before a failure
> >occurs, becuase there is something loading the tank (like an antenna).
> >
> >This is all explained at:
> >
> >http://www.w8ji.com/Vacuum_tube_amps.htm
> >
> >where I walk through the PA system step by step.
> >
> >73 Tom
> >
> >_______________________________________________
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> >Amps@contesting.com
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>
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