‰  NOW 25 WPM  ‰  TEXT IS FROM JANUARY 2016 QST  PAGE 45‰

SEE FIGURE 3, BUT OFTEN IS WELL INTO THE 90S OF PERCENT OF THAT AREA.  THE
RECEIVE APERTURE OF OTHER TYPES OF ANTENNAS CAN BE DETERMINED BASED ON
THEIR GAIN.  FOR EXAMPLE, IF A YAGI ANTENNA HAD A GAIN AT ITS DESIGN
FREQUENCY EQUAL TO THAT OF A PARABOLA OF A PARTICULAR SIZE, IT WOULD
RECEIVE THE SAME ENERGY AND THUS MUST HAVE THE SAME EFFECTIVE APERTURE.
THE EFFECTIVE AREA OF A DIPOLE  A POPULAR AMATEUR ANTENNA IS THE THIN WIRE
DIPOLE.  THIS MAY POSE A QUANDARY, SINCE IT COULD BE MADE ARBITRARILY THIN
AND WILL HAVE THE SAME GAIN EVEN AS THE PHYSICAL AREA VANISHES.  THE
EFFECTIVE APERTURE IS THUS NOT DIRECTLY RELATED TO THE SIZE OF THE SHADOW
IT CASTS, BUT CAN BE RELATED TO HOW WELL IT RECEIVES.  FORTUNATELY, OTHERS
HAVE DERIVED THE DIPOLE APERTURE, SO WE DONT HAVE TO.  KRAUS HAS DETERMINED
THAT THE EFFECTIVE APERTURE OF A HALF WAVE DIPOLE IS, CLOSE TO 0R13 R2,
WHERE IS THE WAVELENGTH, IN THE SAME UNITS AS THAT OF THE DESIRED AREAR.
‰  END OF 25 WPM TEXT  ‰  QST DE W1AW  ƒ