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SR2 – 8
RSSI circuit is controlled by the value the feedback resistor R17. If you are
commonly using a small antenna and listening to weak signals, increase the
value of R17 to customize the response indication of D2, the signal strength
LED.
The final stage, and the real secret to the sensitivity of the receiver, is the
Automatic Gain Control (AGC). The gain control looks at the amount of
signal level present at the output of the demodulator and varies the amount
of gain the Amplifier has accordingly. If there is a strong signal coming
through the demodulator the AGC circuit lowers the gain of the amplifier. If
the receive signal coming through the demodulator is very weak, the AGC
circuit increases the gain of the amplifier (Q2) allowing us to receive signals
from around the world and listen to them with clarity.
SR2 PARTS LAYOUT DIAGRAM