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Donald Pauly of Nevada writes on Saturday, October 20, 2001


"Primary Target"

I'VE worked several years in aircraft radio shops and am a Commercial Pilot with both Airplane and Helicopter ratings.

The primary target is the reflection of the ground transmitted radar signal at approximately 1215 mHz by the body of the aircraft. This reflection is almost always weaker than the secondary target. The secondary target is the signal sent back to the ground by the transponder in the aircraft at 1090 mHz in response to a ground query at 1030 mHz.

This system was developed at the close of WWII and is known in the military as IFF. (Identification Friend or Foe) Civil aircraft are controlled primarily by such means. A pattern of pulses selected by the pilot are sent back to give the controllers a unique identifying number. In most cases the aircraft's altitude is sent back as well. The suicide pilots had turned off this system leaving only the primary return.

This was done to decrease the information available to the controllers and reduce their warning time. I've done it myself many times when joy riding to keep the controllers from knowing my altitude. Civilian FAA controllers use the term target constantly to refer to any radar signal that represents an aircraft. It has nothing to do with any fighter intercept activity.

Donald Pauly


Others make the same point: [1] [2]

© Focal Point 2001 David Irving