‰  NOW 35 WPM  ‰  TEXT IS FROM JANUARY 2016 QST  PAGE 45‰

ANTENNA GAIN, PART III  HOW MUCH SIGNAL GETS RECEIVED?  TRANSMIT GAIN GETS
THE SIGNAL LAUNCHED, BUT HOW STRONG WILL IT BE AT THE RECEIVER?  JOEL R.
HALLAS, W1ZR  IN PARTS I AND II OF THIS SERIES WE TALKED ABOUT WHAT ANTENNA
GAIN IS, THE DIFFERENT WAYS WE CAN SPECIFY IT, AND WAYS TO GET GAIN FROM
ANTENNA STRUCTURESR.  IN THIS PART, PART III , WE WILL CONSIDER WHAT
HAPPENS TO THE SIGNAL AT THE END OF ITS JOURNEY.  WHAT MAKES THE RECEIVED
SIGNAL WEAKER?  LETS START BY LOOKING AGAIN AT A HYPOTHETICAL ISOTROPICALLY
RADIATING ANTENNA IN MYTHICAL FREE SPACE.  AS NOTED IN PART I, SUCH AN
ANTENNA RADIATES EQUALLY IN ALL DIRECTIONS.  IF WE CONSIDER AN IMAGINARY
SPHERE SURROUNDING SUCH A SIGNAL SOURCE, THE SIGNAL RECEIVED ANYWHERE ON
THE SURFACE OF THE SPHERE WILL BE OF EXACTLY THE SAME STRENGTH AS A SIGNAL
RECEIVED ON ANY OTHER PART OF THE SPHERE OF THE SAME AREA.  THIS IS SHOWN
GRAPHICALLY IN FIGURE 1, IN WHICH THE PATCH SHOWN REPRESENTS A RECEIVING
ANTENNA THAT PICKS UP ALL THE SIGNAL COMPONENTS RECEIVED WITHIN THE PATCH
AREA.  IF THE PATCH IN FIGURE 1 WERE SOMEHOW EXTENDED TO COMPLETELY
SURROUND THE SPHERE IN ALL DIRECTIONS, THE RECEIVED SIGNAL WOULD EXACTLY
EQUAL THE TRANSMITTED SIGNAL, REGARDLESS OF THE SIZE OF THE SPHERE.  FROM
THIS IDEA, WE CAN COMPUTE THE ACTUAL POWER THAT CAN BE RECEIVED OVER THE
AREA OF THE RECEIVE ANTENNA SURFACE ITS JUST THE FRACTION OF THE TOTAL
‰  END OF 35 WPM TEXT  ‰  QST DE W1AW  ƒ