Icom IC-551D Instruction Manual page 25

For normal SSB reception, set the AGC switch іп the UP (slow) position. Set the AGC switch
in the FAST (down) position, when tuning or receiving signals with short interval fading.
When in the FAST position, the time constant is shortened.
Р.В. (PASS BAND) TUNING
Receiving USB signal When P.B. TUNE knob is turned
counter-clock wise.
E Ққ,
| + Interfering signal |
_7 Interference Pass band is narrowed
Receiving signal and interfering signal
BFO frequency goes out of the pass band.
Receiving USB signal When P.B. TUNE knob is turned
clockwise.
| 4. Receiving signal
Interference Pass band is narrowed
BFO frequency and interfering signal
Interfering signal goes out of the pass band.
TRANSMITTING
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