Handy gain control in Yaesu FT-840.

 

Very nice job AGC (Automatic gain control) mechanism mostly in Yaesu , Icom , Kenwood etc radios. But some time , usually on low frequency band it suppress dynamical range of receiver . In this time very useful to tune gain by hand.

For operating in contest on low frequency bands , like 160 , 80 , 40 meters , I modify my FT-840:
    1. On main TRX board remove connector J1012.
    2. Mount resistor 7,5k from pin1 to pin3 at J1012 and resistor 2,5k from pin2 to pin3 at J1012 on the main board.
    3. On J1012 jack pin1 mount to ground , pin 2 mount to +9v ( pin4 at J1007 for example ) , pin3 mount to anode of silicon diode (for example 1SS270) , diode cathode mast be connected at point of connections R1026,R1022,R1023.
    4. That's all. Now you have a hand gain control in your receiver on microphone gain knob and no tuning microphone gain on 14 o'clock.