[Boatanchors] 6BA6 Tubes

[Geoff]

And a semi remote is somewhere in between.

Carl
KM1H


----- Original Message ----- 
From: "Rob Atkinson" <ranchorobbo at gmail.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: <boatanchors at mailman.qth.net>; "Al Klase" <al at ar88.net>
Sent: Thursday, December 22, 2011 12:55 PM
Subject: Re: [Boatanchors] 6BA6 Tubes


That remote cutoff grid construction is also used in a tube that was
the secret behind the old broadcast audio gain riding processors made
by GE in the 1960s.

Congratulations on getting the 75A3 operating. It can be made into a
great AM receiver.

73

Rob
K5UUJ

On Thu, Dec 15, 2011 at 9:19 PM, Richard Knoppow
<1oldlens1 at ix.netcom.com> wrote:

> We must have been typing at the same time:-)
> FWIW, the the difference between remote cut-off and
> sharp cut-off tubes is mostly in the physical construction
> of the grids. Sharp cut-off grids have wires which are
> spaced uniformly from end to end. In a remote cut-off tube
> they are widely spaced near the center and become more
> narrowly spaced at both ends. As the bias is increased the
> beam of electrons from the cathode is increasingly blocked
> by the closely spaced wires but can pass through those near
> the center. The result is a gradual cut-off of the beam
> current as bias is increased. In a sharp cut off tube the
> electron beam is decreased uniformly across the grid so it
> is cut off comparitively quickly with increased bias. If you
> have defective tubes you can dissect them and see the
> difference.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
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