‰  NOW 30 WPM  ‰
AT THE FREQUENCY OF INTEREST, THE PRODUCT OF AMPLIFIER GAIN AV IN FIGURE 1
AND FEEDBACK RATIO, IS EQUAL TO OR GREATER THAN 1.  AV IS ALSO KNOWN AS
LOOP GAIN, THE TOTAL GAIN EXPERIENCED BY A SIGNAL ALL THE WAY THROUGH THE
AMPLIFIER, THE FEEDBACK NETWORK AND BACK TO THE INPUT.  THE REQUIREMENT
THAT AV 1 IS FORMALLY KNOWN AS THE BARKHAUSEN CRITERION.  ITS IMPORTANT TO
NOTE THAT 1 IN THIS CASE MEANS AN AMPLITUDE OF 1 AND A PHASE DIFFERENCE OF
0.  IF AV IS NEGATIVE INVERTING, THEN B MUST ALSO BE NEGATIVE, MEANING THE
FEEDBACK MUST HAVE A 180 PHASE SHIFT.  SIGNALS OF THE RIGHT FREQUENCY WILL
BE AMPLIFIED, A PORTION FED BACK TO THE AMPLIFIER INPUT, AMPLIFIED AGAIN,
AND SO ON, BECOMING SELF SUSTAINING AND CREATING A STEADY OUTPUT SIGNAL.
IF THE AMPLITUDE OF THE FEEDBACK IS SUFFICIENT, BUT IF THE PHASE DIFFERENCE
IS NOT EXACTLY RIGHT THEN THE RETURNED PORTION OF THE OUTPUT SIGNAL BECOMES
PROGRESSIVELY FARTHER AND FARTHER OUT OF PHASE ON EACH TRIP.  THE RESULT IS
THAT THE OSCILLATORS OUTPUT CONSISTS MOSTLY OF A FUNDAMENTAL FREQUENCY PLUS
‰  FROM PAGE 97  ‰
K0GX/335 K0HRF/344 K0IUC/350 K0JGH/347 K0JN/357 K0JY/346 K0MN/349 K0NN/347
K0QC/342 K0WK/345 K1AR/349 K1BD/346 K1BV/359 K1EFI/355 K1IK/350 K1JU/340
‰  END OF 30 WPM TEXT  ‰  QST DE W1AW  ƒ