[ARC5] More newbie questions

[Jim Mandaville]

Sean writes:
>
>That makes a difference then.  This is from the SCR-274N manual 15 Feb,
>1943:
>
>"The control grid of r-f amplifier tube V-3 (Tube VT-131) and of the first
>i-f amplifier tube V-5 (Tube VT-131) are returned to ground through a common
>resistor, R-11, in the control grid circuit of the second i-f amplifier tube
>V-6 (Tube VT-131).  The object of this auxiliary gain control circuit is to
>prevent overload of the r-f and i-f amplifier by signals producing as much
>as 2 volts in the antenna circuit.  In effect, it is an automatic gain
>control which is operative only on signals so strong that they would
>otherwise overload the receiver.  When an overload condition arises, the
>second i-f amplifier grid current flows through R-11, making the grid side
>of R-11 negative with respect to ground.  By connecting the grid circuits of
>the r-f and first i-f amplifier to this potential, the gain of these tubes
>will be reduced to the point where overload in these stages is prevented.
>This circuit does not limit the maximum volume that can be obtained from the
>receiver.  The output will be essentially uniform for r-f input signals
>stronger than 100 microvolts (and up to 2 volts)."
>
Aha!  Now I get it.  I was wondering whether R-11 had anything to do with AVC.
This is all clear now, and many thanks for the explanation.

Jim