Directional Antenna

Notice the image of the New Horizon's dish antenna shown on pages 56–57. As you might guess, the bowl-like antenna is a parabolic reflector. This antenna shape helps concentrate and amplify transmission and reception signals. However, the design is highly directional and needs to be aimed with precision if the two-way communication across billions of miles is to be maintained.

In this activity, you'll have the opportunity to explore the properties of a directional antenna. All you need is a metal cooking pot cover and an electronic device with a remote control unit.


Television (or other electronic device) with a remote control unit
Metal pot cover (or wok)

  1. Stand across the room from a television set that can be switched on and off by a remote control unit.
  2. Aim the remote control unit directly at the set and use it to switch the television on. Then switch it off.
  3. Aim the remote control unit directly at the wall to your right side (the beam is now is aimed 90° away from its target). Does your remote still control the television, or is there no longer communication between the TV and the remote?
  4. Aim the beam so that its angle of travel is midway between the TV and the side wall (45° off target). Does the remote communicate with the television?
  5. Keep clicking the remote as you slowly and steadily change the angle of the remote control beam. Stop when you reach the critical angle at which the TV acquires or loses the remote signal. Estimate this angle. If you have a protractor (or other angle-measuring device), record its actual value.
  6. Now aim the remote in the total opposite direction from the television. The beam is now aimed 180° from its target. Test the remote control's capabilities.
  7. Keeping the beam aimed 180° from its target, place a metal pot cover in front of the remote unit. Adjust the metal cover so that the beam is reflected back at the television (see drawing).
  8. Once communication between the remote and the television is established, slowly change the direction of the beam reflected by the metal cover. At what angle is the communication acquired or lost?