The simplest (and
easiest) method to install a gain control is to install a 10Kohm
variable resistor between R15 and R16. This new control can be placed
on the front panel without using shielded leads. I “tombstoned”
R15 (that means tipping it up on one end) and attached one lead to
the vacant end. The other lead went to the (now vacant) solder pad.
Another way is to
remove R15 altogether, install a 10 ohm resistor in series with the
new control, and run both leads from this assembly to the solder pads
where R15 once resided.
controls the supply current to Q1, the receive RF amplifier.
Sensitivity can now be reduced up to 17 dB quite smoothly. A real
help if you often encounter extremely strong signals.
Don Cantrell, ND6T