Question about how a transponder works.?

Question

I am a student pilot and this has bugged me because I cannot figure it out. I know that when you put in the squawk code in your transponder, ATC can see info such as your call sign, speed, alt. etc. Why doesn't some of this information show up when you squawk 1200. Is each particular transponder programmed with the N-Number when it is installed in the aircraft, or does ATC just type into their computer your squawk code and N-number, and the computer will link your squawk code with the n-number so that the n-number will display on the radar screen?

Answer 1

If you are squawking nothing, the controller can only see heading and speed.  Once you squawk 1200, the controller can see altitude.

If you are assigned a unique code, the controller can then put in other info such as aircraft type, destination, routing, requested altitude, etc... but this info is not sent from your aircraft, but is a manual imput on his end.

Hope this helps answer your question.

Answer 2

the ATC radar signal includes a transponder signal that goes to your aircraft.  Then, your aircraft transponder piggy back's a return signal with the code you entered.  No N number information is included.  The computer matches the flight plan information with the transponder code, so the controller can identify you.  They sometimes verify that by asking you to squawk ident.  Airlines use the same codes, but they use flight numbers instead of N numbers for their call signs.  The only way the controller knows your N number is if you tell him, or he reads it off of your tail.

Answer 3

some of it does show up when you squawk a dozen. alt, speed, heading etc. he types your n number when he assigns you a code;

Answer 4

If you get a chance, take a tour through a radar facility such as a control tower or approach control . They will show you and answer all of those questions !

Answer 5

While the above answers are on the right track – Mode A for ‘Squawk’ code, and Mode C for altitude, the latest transponders are Mode S.  These transponders continue to work with the normal Mode A & C ATC system, but additionally these transponders also have a unique 24-bit identifier for each aircraft.  Mode S is required in some non-US controlled airspaces.

All new transponder installations in the US are Mode S.