‰  NOW 25 WPM  ‰  TEXT IS FROM OCTOBER 2018 QST  PAGE 32‰

BUT SWITCHING SUPPLIES SHOULD BE AVOIDED TO MINIMIZE RFI.  ADJUSTMENT  THE
PREAMP ASSEMBLY SHOULD BE PLACED IN ITS APPROXIMATE FINAL LOCATION AND
CONNECTED TO THE SUMMING AMPLIFIER WITH SHIELDED CAT5 CABLE.  CONNECT THE
CAT5 SHIELD TO THE SUMMING AMPLIFIER GROUND AND THE STATION GROUND.  DO NOT
CONNECT THE SHIELD TO THE PREAMP GROUND.  THE DIPOLE ELEMENTS SHOULD BE
LEFT OFF FOR NOW AND REPLACED BY A COUPLE OF 1 K OR SO RESISTORS.  THE
OTHER ENDS OF THE RESISTORS SHOULD BE CONNECTED TOGETHER.  THIS EFFECTIVELY
CONNECTS THE TWO INPUTS OF THE INSTRUMENTATION AMPLIFIER TOGETHER WITH A
LITTLE ISOLATION BETWEEN THEM TO MAINTAIN STABILITY.  APPLY POWER TO THE
SUMMING AMPLIFIER AND CONNECT ITS OUTPUT TO A RECEIVER OR SPECTRUM
ANALYZER.  TUNE IN A LOCAL BROADCAST STATION AND ADJUST R205 FOR MINIMUM
SIGNAL.  THIS OPTIMIZES COMMON MODE REJECTION OF THE SUMMING AMPLIFIER TO
MINIMIZE PICKUP BY THE CAT5 CABLE.  AFTER ADJUSTING R205, REMOVE THE 1 K
‰  END OF 25 WPM TEXT  ‰  QST DE W1AW  ƒ