‰  NOW 40 WPM  ‰  TEXT IS FROM DECEMBER 2013 QST  PAGE 49‰
THEN WIND 10 TURNS ON THE CORE, MAKING SURE EACH TURN IS SNUG ON THE CORE,
SECURING THE FINAL TURN.  I HAVE TRIED BOTH A SINGLE END TO END WINDING AND
THE CROSSOVER STYLE OF WINDING INTRODUCED BY W1JR IN WHICH AFTER HALF THE
TURNS ARE WOUND, THE WINDING CROSSES THROUGH AND OVER TO THE OPPOSITE SIDE
OF THE CORE, THEN CONTINUES TO THE POINT OPPOSITE THE FIRST TURN.  THE
CROSSOVER WINDING HAS LITTLE EFFECT AT HF BUT IT CONVENIENTLY PLACES THE
INPUT AND OUTPUT CONNECTIONS ON OPPOSITE

TIGHTLY COUPLED SO THAT THE CURRENTS ARE EQUAL AND IN OPPOSITE DIRECTIONS.
THAT MEANS THE SAME CURRENT SHOULD FLOW ON THE INSIDE OF THE COAX SHIELD
AND THE CONDUCTOR OF THE LADDER LINE TO WHICH THE SHIELD IS CONNECTED.  IF
ANY OF THE CURRENT ESCAPED ON THE OUTSIDE OF THE COAX FEED LINE AS COMMON
MODE CURRENT, THEN THE BALANCED CURRENT RULE WOULD BE VIOLATED, UPSETTING
THE IMPEDANCE PRESENTED AT THE JUNCTION OF THE TWO FEED LINES.  WHILE THE
COUPLING OF THE TWO CONDUCTORS IN THE FEED LINE SHOULD BE SUFFICIENT TO
GUARANTEE BALANCED CURRENTS IN EACH, ITS A GOOD IDEA TO RAISE THE IMPEDANCE
OF THE COMMON MODE CURRENT PATH, ESPECIALLY BECAUSE YOU DONT KNOW THE
IMPEDANCE OF THAT PATH.  COMMONMODE CURRENT ON FEED LINES CAN CAUSE THE
ANTENNA SYSTEM TO BEHAVE UNPREDICTABLY.  THERE IS ANOTHER REASON TO ADD
SOME COMMON MODE IMPEDANCE TO THE FEED LINE PRESERVING THE SYMMETRY OF THE
ANTENNA SYSTEM.  WITH A BALANCED ANTENNA SUCH AS A DIPOLE OR EDZ,
DECOUPLING OF THE FEED LINES COMMONMODE CURRENT PATH FROM THE ANTENNAS
RADIATED FIELD IS ALSO IMPORTANT, AS EXPLAINED IN W7ELS ARTICLE.  SINCE
COMMON MODE CHOKES ARE DIFFICULT TO CREATE FOR LADDER LINE, I ORIENTED THAT

HANDS ON RADIO H. WARD SILVER, N0AX, N0AX ARRL. ORG  EXPERIMENT 131  COAX
TO OPEN WIRE LINE BALUN  I RECENTLY DESIGNED SOME EXTENDED DOUBLE ZEPP EDZ
ANTENNAS THAT PRESENT A REASONABLE SWR ON 14 AND 21 MHZ.  THE DESIGN USES A
SPECIFIC LENGTH OF 450 LADDER LINE, RESULTING IN AN SWR OF LESS THAN 2 1 AT
THE END OF THE LADDER LINE ON BOTH BANDS.  SINCE THAT LENGTH WAS TOO SHORT
TO REACH THE SHACK, I CHOSE TO TRANSITION FROM THE 450 LINE TO 50 COAXIAL
CABLE.  THE EDZ DESIGN WILL BE PRESENTED IN A FUTURE COLUMN OR ARTICLE.
ONE CAN JUST CONNECT THE COAX TO THE LADDER LINE AND HOPE FOR THE BEST IT
MIGHT WORK, AS SOME DESIGNS FOR MULTIBAND ANTENNAS WILL FUNCTION THAT WAY.
UNFORTUNATELY, THE OUTSIDE OF THE COAX SHIELD IS ALSO CONNECTED AT THE
JUNCTION OF THE TWO FEED LINES, CREATING A COMMON MODE CURRENT PATH WITH
IMPEDANCE DEPENDING ON THE LENGTH OF THE COAX AND THE OPERATING FREQUENCY.
THE BASIC IDEA IS EXPLAINED IN ROY LEWALLENS, W7EL, CLASSIC ARTICLE BALUNS
WHAT THEY DO, AT WWW. EZNEC. COM/ AMATEUR/ ARTICLES/ BALUNS.  PDF.  IF YOU
HAVENT READ IT, THIS WOULD BE A GOOD TIME TO DO SO.  THE CASE FOR USING A
BALUN ROYS ARTICLE SHOWS WHY A CURRENT OR CHOKE BALUN IS NEEDED AT THE
TRANSITION FROM THE COAX TO A DIPOLE WITH THE WIRES AT RIGHT ANGLES TO THE
COAX.  WHAT IF INSTEAD OF A DIPOLE, THE COAX IS CONNECTED TO LADDER LINE?
IS A BALUN STILL NECESSARY?  IN TRANSMISSION LINES, THE CONDUCTORS ARE
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ