‰  NOW 40 WPM  ‰  TEXT IS FROM OCTOBER 2012 QST  PAGE 44‰
T1 AND REPRESENTS THE SUM OF THE SIGNALS FROM LOOP 1 AND LOOP 2.  FOR BEST
RESULTS, BOTH AMPLIFIERS SHOULD OFFER ISOLATION BETWEEN THE INPUT AND
OUTPUT, BE BALANCED TO MINIMIZE SECOND ORDER HARMONICS AND SHOULD HAVE A
HIGH COMPRESSION POINT.  ANOTHER VERSION OF THE COMBINER AMPLIFIER
UTILIZING A PASSIVE INPUT COMBINER C1 IS SHOWN IN FIGURE 5.  HERE, THE
SIGNALS FROM PORT A AND PORT B ARE COMBINED IN COUPLER C1.  ONE SUITABLE
CIRCUIT FOR SUCH A COUPLER CAN BE FOUND 

CONDUCTIVE MAST GUIDES THE VERTICAL SIDE OF TWO IDENTICAL RIGHT
TRIANGULARSHAPED WIRE LOOPS TO FORM A COMMON OR SHARED APEX.  EACH LOOP IS
DRAPED IN A SYMMETRICAL MANNER ABOUT THE MAST, ORIENTED IN A COMMON
VERTICAL PLANE, AND HELD IN TENSION BY AN ANCHOR FORMING A HORIZONTAL BASE
THAT IS SPACED A FEW INCHES ABOVE THE GROUND.  EACH LOOP IS CONSTRUCTED AS
AN ENDLESS WIRE LOOP THAT IS ROUTED THROUGH A GROUP OF FERRITE CORES
FORMING A CURRENT TRANSFORMER ACTING AS A COUPLING LINK.  THE COUPLING LINK
IS POSITIONED AT A DISTANCE FROM THE MAST AND IS CONNECTED SO THAT THE
ANCHOR SIDE OF THE TRANSFORMER IS CONNECTED TO THE CENTER COAX CONDUCTOR OF
A LOOP FEED LINE.  THE LOOP FEED LINE FROM LOOP 1 IS CONNECTED TO A
REFERENCE LINE.  THE OPPOSITE END OF THE REFERENCE LINE CONNECTS TO AN
INPUT PORT OF A COMBINER AMPLIFIER THAT WILL BE DESCRIBED LATER IN THIS
ARTICLE.  THE LOOP 2 COUPLING LINK IS POSITIONED AT A DISTANCE FROM THE
MAST AND IS CONNECTED SO THAT THE ANCHOR SIDE OF THE TRANSFORMER IS
CONNECTED TO THE CENTER COAX CONDUCTOR OF A LOOP FEED LINE.  THE OPPOSITE
END OF THE FEED LINE IS CONNECTED TO A DELAY LINE.  THE OPPOSITE END OF THE

THE SHARED APEX LOOP ARRAY THIS COMPACT DIRECTIONAL WIDEBAND RECEIVING
ANTENNA CAN REDUCE INTERFERENCE.  MARK BAUMAN, KB7GF  EFFECTIVE RECEIVING
ANTENNAS ARE BECOMING AN INDISPENSIBLE PART OF OUR AMATEUR ARSENAL AS WE
BATTLE INTERFERENCE FROM BOTH NATURAL AND MAN MADE SOURCES.  MANY OF US DO
NOT HAVE THE ACREAGE TO ERECT DIRECTIONAL ANTENNAS, ESPECIALLY ON THE LOWER
BANDS, SO WE USE SHORTENED VERTICALS AND LOW HANGING DIPOLES, WHICH PROVIDE
ESSENTIALLY OMNIDIRECTIONAL RESPONSE.  AS A RESULT, OUR EARS ARE BOMBARDED
WITH SIGNALS AND INTERFERENCE FROM ALL DIRECTIONS WHEN OUR TRANSMITTING
ANTENNA DOUBLES AS OUR RECEIVING ANTENNA.  ANTENNA CONCEPT TO ASSIST IN
THIS BATTLE, I DESIGNED A COMPACT DIRECTIONAL RECEIVING ANTENNA THAT
EFFECTIVELY REDUCES INTERFERENCE OVER A WIDE FREQUENCY RANGE.  THE ARRAY
DESCRIBED HERE IS COMPACT, HAVING A LOOP SPACING OF ONLY 2 INCHES, A 10
FOOT TALL MAST, AN ARRAY LENGTH OF 20 FEET AND A BASE HEIGHT OF 6 INCHES.
IN THIS CONFIGURATION, THE ARRAY DELIVERS DIRECTIVITY OVER A FREQUENCY
RANGE OF 500 KHZ TO 22 MHZ AND EXCEPTIONAL SENSITIVITY ABOVE 6 MHZ.  A
GROUND MOUNTED VERSION OF THE SHARED APEX LOOP ARRAY IS SHOWN IN FIGURE 1
AND SCHEMATICALLY IN FIGURE 2.  THE ANTENNA UTILIZES TWO CLOSELY SPACED
LOOPS THAT ARE INTERCONNECTED VIA A DELAY LINE TO DELIVER HEALTHY FRONT TO
SIDE AND FRONT TO BACK RATIOS OVER A WIDE FREQUENCY RANGE.  A NON
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ