‰  NOW 25 WPM  ‰  TEXT IS FROM DECEMBER 2008 QST  PAGES 33, 35 AND 74  ‰

THINK OF ANY ONE OF THE SWITCH OUTPUTS AS BEING THE 0 PHASE REFERENCE, THEN
THE NEXT ONE IN SEQUENCE SAMPLES AT THE 90 POINT, THE NEXT SWITCH SAMPLES
AT 180 AND THE NEXT, AT 270.  THIS SEQUENCE REPEATS AD INFINITUM.  THE
SAMPLE VOLTAGE LEVELS OF THE FOUR PHASES ARE STORED IN CAPACITORS C1, C5,
C10 AND C13.  WHEN THE 180 SAMPLE IS INVERTED AND COMBINED WITH THE 0
SAMPLE AND APPROPRIATELY FILTERED, THE RESULT IS THE IN PHASE, OR I,
COMPONENT OF THE SIGNAL AT ONE QUARTER OF THE SAMPLE RATE.  C1 AND C5 STORE
THE SAMPLES AND PROVIDE THE FILTERING FOR THE I CHANNEL, WHILE OP AMP U2A
DOES THE INVERTING AND COMBINING.  U3A GIVES A GAIN BOOST AND ADDITIONAL
FILTERING.  SIMILARLY, THE 90 AND 270 SAMPLES ARE STORED IN C10 AND C13 AND
COMBINED IN U2B FOLLOWED BY U3B TO GENERATE THE QUADRATURE, OR Q,
COMPONENT.  TRIMMER RESISTOR R15 IS USED TO ADJUST THE GAIN OF THE Q
‰  FROM PAGE 74  ‰
IL Joplin ARC W0IN 404 2 12 2,300 MO Nashville ARC K4CPO 473 2 12 2,292 TN
‰  END OF 25 WPM TEXT  ‰  QST DE W1AW  ƒ