‰  NOW 30 WPM  ‰

300 600 TO WORK PROPERLY WITH A 50 TRANSCEIVER, AN IMPEDANCE TRANSFORMER OR
ANTENNA TUNER IS NEEDED.  THE RADIO ENERGY IS CARRIED BY THE COAX TO THE
ANTENNA.  AGAIN, FOR MAXIMUM POWER TRANSFER, THE ANTENNAS IMPEDANCE MUST BE
50 IF ITS NOT, AND THE ANTENNAS IMPEDANCE IS, SAY, 100, THEN THE TWO ARENT
MATCHED AND PART OF THE POWER FROM THE COAX IS REFLECTED BACK TO THE
TRANSMITTER.  ITS EASIEST TO THINK OF THIS REFLECTED POWER IN TERMS OF
VOLTAGE.  IF THE LINE IS MATCHED, THERE IS NO REFLECTION AND THE VOLTAGE
EVERYWHERE ALONG THE COAX IS THE SAME, WHICH MEANS THAT THE STANDING WAVE
RATIO SWR IS 1 1.  IF THE ANTENNA AND COAX ARE MISMATCHED, THEN PART OF THE
VOLTAGE THAT REACHES THE ANTENNA IS REFLECTED BACK DOWN THE COAX TO THE
TRANSMITTER.  AT THE SAME TIME, THE TRANSMITTER IS STILL DRIVING VOLTAGE
FORWARD TOWARD THE ANTENNA.  WHEN THE FORWARD VOLTAGE WAVE MEETS THE
REFLECTED REVERSE VOLTAGE WAVE THE TWO MIX TOGETHER.  IN SOME PLACES ON THE
COAX THEY ADD AND AT OTHER SPOTS THEY SUBTRACT, CREATING A STANDING WAVE ON
THE COAX.  THE RATIO OF THE HIGHEST AND LOWEST AMPLITUDES OF THE STANDING
WAVE ALONG THE COAX GIVES US THE SWR.  THE GREATER THE MISMATCH, THE HIGHER
‰  END OF 30 WPM TEXT  ‰  QST DE W1AW  ƒ