‰  NOW 40 WPM  ‰  TEXT IS FROM SEPTEMBER 2013 QST  PAGE 36‰
DIRECTION CONTROL LINE IS ENERGIZED WHEN THE PUSH SWITCH IS MOMENTARILY
PRESSED.  THIS LINE IS HARD WIRED AT THE MATRIX TO THE LOGIC INPUTS THAT
ENSURE THAT EACH OF THE FOUR ELEMENTS IS DRIVEN APPROPRIATELY.  IN
ADDITION, THE MATRIX HAS THREE RF INPUTS AND FOUR RF OUTPUTS.  BECAUSE OF
THE LOW LOAD REQUIREMENTS, THE POWER FOR THE CONTROL OF THE ARRAY WAS
SUPPLIED BY A 6 V BATTERY.  INTERCONNECTIONS THE BOX WAS LINKED TO THE
OPERATING POSITION BY A SEVEN CONDUCTOR 

COMMON NODE INPUT IMPEDANCE OF 51 J29 FOR THE FINISHED ARRAY.  THE DETAILS
OF THE TRANSFORMERS ARE SUMMARIZED IN TABLE 4.  TABLE 4 SHOWS THAT MORE
PRIMARY TURNS WERE REQUIRED THAN HAD BEEN ANTICIPATED BY A SIMPLE VIEW OF
TRANSFORMER DESIGN.  THIS COULD BE DUE TO WINDING END EFFECTS WHERE THE END
TURNS COUPLED INEFFICIENTLY TO THE CORE.  CAREFUL ADJUSTMENT OF THE NUMBER
OF TURNS WAS MADE AS MEASUREMENTS CHECKED THE OPEN CIRCUIT VOLTAGE RATIO.
SMALL ERRORS IN ACHIEVING THE SPECIFICATION ARE DUE TO AN INABILITY TO
REALIZE FRACTIONAL TURNS.  THE ATTENUATION OF EACH TRANSFORMER WAS ABOUT
1R2 DB, EQUIVALENT TO A TRANSFORMATION EFFICIENCY OF 76.  THE REALIZATION
OF THE TRANSFORMERS REQUIRED GREAT CARE, BUT THERE IS CERTAINLY SCOPE FOR
FURTHER IMPROVEMENT HERE.  THE DIRECTION CONTROL SYSTEM IN ORDER TO DIRECT
THE BEAM TO ONE OF THE FOUR DIAGONAL DIRECTIONS THE FEEDS TO THE ELEMENTS
HAVE TO BE REROUTED, IDEALLY UNDER ELECTRICAL CONTROL.  FIGURE 6 SHOWS THE
TOPOLOGY OF A SWITCHING MATRIX FOR ROUTING THE THREE POSSIBLE PHASE SHIFTED
FEEDS TO THE APPROPRIATE ELEMENTS FOR A PARTICULAR DIRECTION OF FIRE.  THE
SWITCHES USED WERE RF LATCHING REED RELAYS WITH A CURRENT CARRYING RATING

AT THE SAME POSITION.  THIS HELPED TO MINIMIZE THE LOCAL POTENTIAL
DIFFERENCES BETWEEN THE WINDINGS ENSURING THAT CAPACITIVE CURRENTS BETWEEN
THE WINDINGS WERE MINIMIZED.  THE WINDING SCHEME IS SHOWN IN FIGURE 5.  IN
PRACTICE 20 PRIMARY TURNS WERE SELECTED FOR EACH TRANSFORMER BECAUSE THESE
FITTED CONVENIENTLY ONTO THE CHOSEN TOROIDS.  THE NUMBERS OF SECONDARY
TURNS FOR THE TWO TRANSFORMERS WERE THEN ADJUSTED MATHEMATICALLY TO ACHIEVE
A SUITABLE VALUE FOR THE PARALLELED PRIMARY REFLECTED IMPEDANCES, ALWAYS
PRESERVING THE REQUIRED RATIO BETWEEN THE TWO SECONDARIES.  THE SETTING OF
THE NEUTRALIZING TRIMMERS HAS TO BE DONE WHEN THE SECONDARY IS TERMINATED
WITH A RESISTANCE.  IN THIS CASE THE LOAD RESISTANCE WAS 100.  WHEN EACH
PRIMARY IS EXCITED WITH A VOLTAGE AT THE DESIGN FREQUENCY THE SECONDARY
VOLTAGE IS OBSERVED.  IF A HIGH IMPEDANCE OSCILLOSCOPE IS AVAILABLE, THE
PHASE OF THE PRIMARY AND SECONDARY VOLTAGES CAN BE COMPARED AND THE TRIMMER
ADJUSTED UNTIL THE PHASE DIFFERENCE IS ZERO.  THIS CONDITION ALSO
CORRESPONDS TO A MAXIMUM IN THE SECONDARY VOLTAGE, SO THAT AN OBSERVATION
OF THIS RF VOLTAGE WITH A SIMPLE DIODE RF PROBE AND A DC VOLTMETER WOULD
SUFFICE.  ONCE THIS PROCEDURE HAS BEEN CARRIED OUT THE INDIVIDUAL
TRANSFORMERS CAN BE CONNECTED TO THE POWER SPLITTER CIRCUIT WITHOUT FURTHER
ADJUSTMENT.  THE OVERALL DESIGN PROCEDURE LED EVENTUALLY TO A MEASURED
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ