[Hallicrafters] SX-117 AVC Voltage Measurements and Changing "S" Meter Indications.

[Bill Gerhold]

The continuing story of the SX-117 "S" meter, and how it changes
with different selectivity settings.  This is why it changes.

I measured the AVC voltage on tube V7, pin # 1.  The following are
my findings with an "S5" received signal:

Selectivity Control         AVC Voltage on Pin # 1

5 khz                        - 0.84 vdc
2.5 khz                      - 1.09 vdc
5.0 khz                      - 1.37 vdc

V7 is a 6DC6 tube and is used as a 1650 khz amplifier of which
the "S" meter is in the cathode circuit.

Tube V10b, is the 6BN8 tube or AVC rectifier which is connected
directly to the selectivity switch.  The selectivity switch switches
in (2) different resistive values including (2) different capacitor
values in the 2nd IF circuit.  These (2) added components to the 2nd IF
circuit, provide the 2.5 and .5 receiver bandwidths.

The resistive values are also connected to the 6BN8 AVC rectifier cathode
circuit and the 2nd IF, thereby loading or unloading the AVC line which
explains the varying "S" meter readings when the selectivity Control is
changed.  I hope I got that right.

K2WH