Fw: Re: [Boatanchors] Tube data

[windy10605 at juno.com]

They generally draw more filament current, have larger cathodes, and emit
more electrons. Many are designed for "off" and "on" (computer use).
However I have also heard they are excellent for frontends due to "low
noise". On the one hand "hot filaments" and "low noise" don't seem to fit
together but I've seen several articles using 7044 dual triodes in the RF
section.

They are also good for higher power at lower voltage when compared to the
others if you are interested in such. But, not as much as "space charge"
tubes ....but that's another story.

73 Kees K5BCQ 



-------- Forwarded message ----------
From: "J. Forster" <jfor at quik.com>
To: telegrapher at att.net
Cc: boatanchors at mailman.qth.net
Date: Tue, 24 May 2005 01:18:04 -0400
Subject: Re: [Boatanchors] Tube data
Message-ID: <4292B90C.CF224181 at quik.com>
References: <4292B314.2040908 at att.net>

telegrapher at att.net wrote:

> The 6919 is a "high Perveance twin Diode" for use in Computers.  O,
> what's "High Perveance" mean?

Google finds:

                Perveance is related to conductance. It depends on
cathode
surface area, on its temperature and on
                the electron emitting properties of the cathode
materials.
Doubling perveance is equivalent to placing
                two identical tubes in parallel.

> The other, a 6687/E-91H is a dual control heptode used in computers.
> Since tube based computers were before my time, what actually were
these
> two used for?

Making gates or Flip-Flops.

-John

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