‰  NOW 13 WPM  ‰  TEXT IS FROM JANUARY 2016 QST PAGE 54  ‰

DIGITAL SIGNAL, THE AUDIO OUTPUT WILL ALSO CONSIST OF MANY FREQUENCIES.  AS
THE LO FREQUENCY IS CHANGED, SO WILL THE FREQUENCY OF THE MIXER OUTPUT
SIGNAL THAT IS INPUT TO THE IF FILTER, WHICH IS CENTERED AT A FIXED
FREQUENCY.  AS LONG AS THE MIXER OUTPUT SIGNAL IS WITHIN THE IF FILTER
PASSBAND, IT WILL BE AMPLIFIED AND PASSED TO THE PRODUCT DETECTOR.  SINCE
THE AUDIO FREQUENCY IS THE DIFFERENCE BETWEEN THE IF OUTPUT SIGNAL AND THE
BFO, CHANGING THE LO FREQUENCY WILL ALSO CHANGE THE FREQUENCY OF THE AUDIO
ƒ  QST DE W1AW  ‰
OUTPUT BY MOVING IT AROUND IN THE IF FILTER PASSBAND.  INSTEAD OF MOVING
THE RECEIVER IF PASSBAND TO FIND RF SIGNALS, THE RF SIGNALS ARE COMBINED
WITH THE VARIABLE LO SO THE MIXER OUTPUT IS WITHIN THE IF FILTER PASSBAND.
THEY ARE THEN AMPLIFIED AND CONVERTED TO AUDIO SIGNALS.  IN ANALOGY,
INSTEAD OF MOVING A TELESCOPE TO LOOK AT A STAR, THE TELESCOPE REMAINS
STATIONARY AND THE STAR MOVES INTO THE TELESCOPES FIELD OF VIEW.  THATS
‰  END OF 13 WPM TEXT  ‰  QST DE W1AW  ƒ