[HBR] Re: GB> RSGB Keyer

[Chris Trask]

    Give it a break, Mike.  We're discussing circuitry and helping a fellow
get a project running.  It's not yet another opportunity for you to beat
people over the head with your obscure ideology.

Chris

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----- Original Message -----
From: "Mike McCarty" <Mike.McCarty at sbcglobal.net>
To: "Chris Trask" <christrask at earthlink.net>
Cc: "Ian Wilson" <ianmwilson73 at gmail.com>; "EP Swynar" <gswynar at durham.net>;
<hbr at mailman.qth.net>; "Old Tube Radios"
<glowbugs at piobaire.mines.uidaho.edu>
Sent: Tuesday, May 27, 2008 5:29 PM
Subject: Re: GB> RSGB Keyer


> Chris Trask wrote:
> >>> timing capacitor charges, and the speed pot/resistor determines the
> >>> discharge time.  The inductance of the transformer increases the dwell
> > time,
> >>> and that may be where Ed is having his trouble.
> >>>
> >>>     The second triode is just a voltage-to-current converter, with the
> >>> weight potetiometer setting the point at which the relay drops in and
> > out.
> >> This conflicts with your statement that it's a multivibrator, which
> >> requires two gain stages.
> >>
> >
> >     Try using the simpler term "timer", if it's easier for you to
> > comprehend.
>
> Condescension is always so unattractive, don't you think?
>
> It isn't a matter of comprehension. I comprehend what you wrote. It's
> just that what you wrote is incorrect. A multivibrator is two inverting
> gain stages with the output of each connected to the input of the other.
> A timer is not an MV (necessarily) nor is an MV a timer (necessarily).
> Even if the first stage were a timer[*], it is not a multivibrator.
>
> I'm all for generalizing and seeing correspondences between different
> kinds of circuits for purposes of understanding their behavior in
> multiple ways, but I can't quite stretch a single stage like that
> into being a multivibrator.
>
> Considering the second stage as a V/I converter is a bit of a stretch,
> though a somewhat reasonable one. The plate current at zero grid voltage
> (first stage here) is about 30 mA or so. That means that the first
> stage is capable of saturation. If this occurs (which it will) the
> cathode will have about -40V on it, coupled to the grid of the second
> stage. The second stage cathode voltage is variable from about -120V to
> -92V. That means that the second stage is going to be definitely
> saturated. When the first stage is cut off (like key up) the grid of
> the second tube is at -120V, so it will be cut off (when the "weight"
> control is adjusted to midpoint, say about 110V) since the grid
> will then be about 10V negative relative to the cathode.
>
> It's a bit of a stretch to call it a V/I converter when it operates in a
> digital mode.
>
> [*] I'm trying only to address the point you make here. Exactly how
> the first stage operates is a separate issue.
>
> mike
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