‰  NOW 20 WPM  ‰   TEXT IS FROM JULY 2014 QST  PAGE 34‰

DB/S UNIT TO 7 DB/S UNIT.  BE AWARE THAT YOU CANT USE ANY OLD OPERATIONAL
AMPLIFIER BECAUSE THE INPUT AND OUTPUT VOLTAGE OF THE AMPLIFIERS MUST BE
ABLE TO ACCOMMODATE 0R8 V, WHICH IS CLOSE TO THE POSITIVE RAIL OF 0 V.  THE
TLV2372 HAS INPUT AND OUTPUT CAPABILITY ALL THE WAY TO THE SUPPLY RAILS
POTENTIOMETER R2 ZERO PROVIDES A ZERO ADJUSTMENT FOR THE S METER, WHICH IS
BUFFERED THROUGH AMPLIFIER U1B.  THE ZERO FUNCTION OPERATES DIFFERENTLY
FROM MOST.  DIODE D3 TRANSFORMS THE AMPLIFIER INTO A PRECISION RECTIFIER.
THE RESULT IS THAT THE S METER CANNOT BE DRIVEN BELOW ZERO.  THE REASON FOR
ADDING THIS FEATURE IS THAT IF THE VALUE OF C137 SEE FIGURE 1 IS INCREASED
BY A LARGE AMOUNT IN ORDER TO INCREASE THE AGC DECAY TIME AS I DID IN MY
RECEIVER, SWITCHING FROM STANDBY TO OPERATE CAN RESULT IN A NEGATIVE METER
‰  END OF 20 WPM TEXT  ‰  QST DE W1AW  ƒ