‰  NOW 25 WPM  ‰  TEXT IS FROM AUGUST 2006 QST  PAGES 52, 53 AND 97  ‰
SMALL AMOUNTS OF OTHER SIGNALS, USUALLY HARMONICS, FOR WHICH LOOP GAIN IS
SUFFICIENT AND THE ROUND TRIP PHASE DIFFERENCE IS SOME INTEGER MULTIPLE OF
360.  WHERE DOES THE NECESSARY PHASE SHIFT COME FROM?  SOME OF THE PHASE
SHIFT MAY COME FROM THE AMPLIFIER ITSELF.  FOR EXAMPLE, AN AMPLIFIER SUCH
AS A COMMON EMITTER AMPLIFIER EXPERIMENT 1 OR AN OP AMP CONNECTED TO INVERT
ITS INPUT SIGNAL HAS A PHASE SHIFT OF 180.  THE REMAINING PHASE SHIFT MUST
COME FROM AN EXTERNAL PHASE SHIFT NETWORK, JUST AS WE SAW IN EXPERIMENT 17.
ANY KIND OF DEVICE OR CIRCUIT THAT PRODUCES A CONSTANT PHASE SHIFT CAN BE
USED, INCLUDING RC OR LC CIRCUITS AND EVEN TRANSMISSION LINES.  IF THE
AMPLIFIER IS NON INVERTING, SUCH AS AN EMITTER FOLLOWER EXPERIMENT 2, THE
FEEDBACK SIGNAL MUST BE IN PHASE WITH THE OUTPUT SIGNAL.  AS LONG AS THE
REQUIREMENTS FOR TOTAL LOOP GAIN AND PHASE ARE SATISFIED, THE OSCILLATOR
‰  FROM PAGE 97  ‰
K1KM/344 K1KO/340 K1KOB/341 K1NOK/347 K1UO/348 K1WER/338 K1YR/350 K2AJY/339
‰  END OF 25 WPM TEXT  ‰  QST DE W1AW  ƒ