=  NOW 40 WPM  =

ANTENNA IS THE RESONANT HALF WAVE DIPOLE, WHICH HAS THE BENEFICIAL
PROPERTY THAT IF YOU FEED IT AT THE CENTER, WITH THE TWO ELEMENTS
EACH A QUARTER WAVELENGTH LONG, THE FEED POINT IMPEDANCE HAS NO
REACTANCE AND IS PURELY RESISTIVE.  THUS, IT IS EASY TO MATCH FOR
MAXIMUM POWER TRANSFER FROM THE TRANSMITTER VIA A COAXIAL FEEDLINE.
BUT ON A FULL WAVELENGTH DIPOLE, A CENTER FEED LOCATION IS ACTUALLY
AN EXTREMELY HIGH IMPEDANCE POINT.  LETS LOOK AT FIGURE 2, WHICH
DEPICTS THE RMS ASK DAVE MYSTERY BALUNS, REVIVING A RADIO, DIPOLES,
AND MORE ON SPLATTER DETERMINING A BALUN OR UNUNS RATIO Q I HAVE A
COMMERCIALLY MADE BALUN IN MY JUNK BOX THAT I ONCE USED FOR A WHILE
AND WOULD LIKE TO AGAIN, BUT THE LABEL HAS FADED.  ITS EITHER 1 1 OR
4 1.  IS THERE ANY TEST I CAN DO TO FIND OUT?  A ABSOLUTELY, AND YOU
PROBABLY HAVE THE REQUIRED EQUIPMENT IN YOUR HAM SHACK ALREADY.  YOU
NEED A RESISTANCE OF KNOWN VALUE USE A RESISTOR, OR EVEN YOUR DUMMY
LOAD AS WELL AS AN ANTENNA ANALYZER.  PLACE THE KNOWN RESISTANCE
ACROSS THE OUTPUT TERMINALS OF THE BALUN, THEN CONNECT THE ANTENNA
ANALYZER AS THOUGH YOU WERE MEASURING SWR, I RECOMMEND SWEEPING
ACROSS A WIDE SECTION OF THE 80 METER BAND.  THE ANALYZER WILL
TYPICALLY MEASURE AND DISPLAY BOTH THE RESISTANCE AND THE REACTANCE.
ESPECIALLY IN THE HF BANDS, THE REACTANCE SHOULD BE VERY LOW, BUT
WERE JUST INTERESTED IN THE RESISTANCE MEASUREMENT.  MY TEST SETUP
IN FIGURE 1 USES A 100 RESISTOR.  ON THIS 4 1 BALUN WE WOULD EXPECT
A READING OF APPROXIMATELY 25.  THE ANTENNA ANALYZER ACTUALLY READS
28, WHICH IS CLOSE ENOUGH TO CONFIRM THAT THE BALUN IS 4 1, AS
INDICATED ON THE LABEL.  WITH A 1 1 BALUN, WE WOULD EXPECT A READING
APPROXIMATELY EQUAL TO THE VALUE OF THE RESISTANCE.  PLEASE NOTE
THAT HAM RADIO QUALITY TEST GEAR IS USUALLY INEXPENSIVE AND MAY GIVE
RESULTS THAT ARE ONLY CLOSE TO THE EXPECTED VALUE.  AS YOU TUNE THE
ANTENNA ANALYZER ACROSS THE HF BAND, YOU WILL SEE SOME VARIATIONS IN
THE MEASURED VALUES OF RESISTANCE AND REACTANCE.  THAT IS WHY A LOW
BAND SUCH AS 80 METERS IS IDEAL FOR THE MEASUREMENTS, AND IN
SWEEPING ACROSS A WIDE ENOUGH SPECTRUM YOU SHOULD GET AN IDEA OF
WHAT THE MEASURED RESISTANCE TENDS TO LEVEL OFF AT, SO YOU CAN
IGNORE POSSIBLE FREQUENCY RELATED ABERRATIONS.  IT SHOULD BE EASY
AND OBVIOUS TO TELL WHETHER THE BALUN IS 1 1 OR 4 1.  YOU CAN FIND A
VIDEO THAT SHOWS THIS MEASUREMENT PROCESS ON THE ARRL YOUTUBE
CHANNEL.  BRINGING A SWAN BACK TO LIFE Q I AM TRYING TO REPAIR A
SWAN 750CW HF TRANSCEIVER THAT EMITS SMOKE.  I HAVE A SCHEMATIC WITH
PIN TO CHASSIS VOLTAGES, BUT NEED A LIST OF TUBE PIN TO CHASSIS
RESISTANCES.  CAN YOU HELP?  A IM VERY SORRY, I DONT HAVE A READY
ANSWER FOR YOU.  BUT IF THE UNIT IS SMOKING, UNPLUG IT AND LEAVE THE
POWER OFF UNTIL YOU HAVE FOUND THE CAUSE.  OLD RADIOS OFTEN SUFFER
FROM COMPONENT AGING.  RESISTORS, FOR EXAMPLE, CAN DRIFT TO VALUES
WILDLY DIFFERENT FROM WHAT IS MARKED ON THEM.  BUT CAPACITORS, MORE
THAN ANYTHING, CAN POSE THE BIGGEST PROBLEMS.  RADIO RESTORERS OFTEN
REPLACE ALL THE CAPACITORS WITH MODERN COMPONENTS AS THEIR
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