‰  NOW 40 WPM  ‰  TEXT IS FROM AUGUST 2006 QST  PAGES 38, 39 AND 96  ‰

THE COMPACT QUAD MULTIBAND HF ANTENNA AN EASY TO BUILD LOOP WITH A SIMPLE
MATCHING SECTION OFFERS FOUR BAND HF COVERAGE.  ANDREW ROOS, ZS6AAA WHEN I
RELOCATED TO JOHANNESBURG I NEEDED A NEW MULTI BAND HF ANTENNA.  SINCE I
WAS STAYING IN A RENTED HOUSE, A TOWER WAS OUT OF THE QUESTION, BUT
FORTUNATELY MY LOVELY WIFE HAD TAKEN MY NOT SO SUBTLE HINTS AND GIVEN ME A
SPIDERBEAM 39 FOOT TELESCOPIC POLE FOR MY BIRTHDAY.  THE POLE IS MUCH
STIFFER THAN A FISHING ROD, BUT STILL ONLY SUITABLE FOR A VERY LIGHTWEIGHT
ANTENNA.  THIS RULED OUT TRAP DIPOLES SUCH AS THE W3DZZ, AS THE TRAPS WOULD
HAVE BEEN TOO HEAVY.  THE GARDEN, WHICH MEASURED ONLY 66 X 46 FEET, WAS TOO
SMALL TO ACCOMMODATE A G5RV.  THE LOCATION OF THE SHACK ON THE OPPOSITE
SIDE OF THE HOUSE FROM THE GARDEN MADE AN OPEN WIRE FED DOUBLET
IMPRACTICAL.  I RULED OUT MOST OF THE STANDARD MULTIBAND HF ANTENNAS AND
DECIDED TO DEVELOP MY OWN.  A CLOSED LOOP SEEMED TO BE A GOOD STARTING
POINT SINCE LOOPS ARE NATURALLY RESONANT ON ALL MULTIPLES OF THEIR
FUNDAMENTAL FREQUENCY.  THIS MATCHES THE HARMONIC RELATIONSHIPS BETWEEN THE
MOST POPULAR AMATEUR BANDS.  THEY CAN BE FED AT THE BOTTOM OF THE LOOP, SO
‰  FROM PAGE 96  ‰
KJ9I/342 KK0M/341 KK0U/345 KK2I/346 KL7J/342 KL7RA/349 KN0V/344 KN4F/343
KP4BJD/352 KQ9W/341 KR5C/347 KR9U/341 KT9T/353 KU4J/346 KY7M/344 KZ2P/344
LA2QM/341 LA4CM/350 LA5XGA/341 LA7QI/349 LA7SI/342 LA8XM/341 LA9XG/341
‰  QST DE W1AW  ƒ

THE WEIGHT OF THE FEED LINE DOES NOT HAVE TO BE SUPPORTED BY THE HIGHER AND
THINNER SECTIONS OF THE MAST.  UNFORTUNATELY, THE 39 FOOT HIGH MAST WAS NOT
TALL ENOUGH TO SUPPORT A 40 METER LOOP, AND A 20 METER LOOP WOULD ONLY
PROVIDE COVERAGE OF THE 20 AND 10 METER BANDS THROUGH THE HARMONIC
RELATIONSHIPS.  AT THIS LOW POINT IN THE SUNSPOT CYCLE, I ALSO WANTED TO BE
ABLE TO WORK THE 40 AND 15 METER BANDS.  FORTUNATELY A LOOP WHICH IS N /2
LONG IS ALSO RESONANT THE REACTIVE COMPONENT OF ITS IMPEDANCE IS ZERO,
ALTHOUGH IT HAS A VERY HIGH IMPEDANCE AS HIGH AS 50 K FOR THE /2 LOOP.
THIS HIGH RESISTIVE IMPEDANCE CAN BE TRANSFORMED TO A LOW IMPEDANCE USING A
/4 MATCHING SECTION OF THE RIGHT CHARACTERISTIC IMPEDANCE.  TO TRANSFORM 50
K TO 50 WOULD REQUIRE A MATCHING SECTION WITH A CHARACTERISTIC IMPEDANCE Z0
OF ABOUT 1600, WHICH IS NOT FEASIBLE.  HOWEVER A QUARTER WAVE MATCHING
SECTION WITH A Z0 OF 800 ABOUT THE MAXIMUM PRACTICAL IMPEDANCE WOULD
TRANSFORM 50 K TO APPROXIMATELY 13, RESULTING IN AN SWR OF 4 1 ON 50 COAX.
‰  FROM PAGE 96  ‰
LU2NI/341 LU3MCJ/343 LY2ZZ/349 LZ1HA/342 LZ2CC/346 N0AT/351 N0AV/351
N0TB/354 N0XA/346 N1DCM/341 N1XX/367 N2TK/347 N2TU/341 N3AM/346 N3BNA/341

SOUTH AFRICA, AND I DIDNT WANT THE ADDITIONAL WEIGHT OF PVC INSULATION.  IF
YOU ARE ABLE TO OBTAIN HARD DRAWN COPPER WIRE, IT WOULD BE A BETTER CHOICE
AS IT IS STRONGER AND LESS LIKELY TO STRETCH.  THE ANTENNA AND MATCHING
SECTION TOGETHER REQUIRE ABOUT 144 FEET 
‰  FROM PAGE 96  ‰
N6KK/345 N6OJ/352 N6UC/360 N6VR/354 N7BK/341 N7FU/349 N7HN/345 N7KH/345

‰  END OF 40 WPM TEXT  ‚