Radio Aids and Surveillance Systems
Surveillance fundamentals
Know the difference between primary radar (skin paint) and secondary surveillance radar (SSR), and how Mode A, C and S work. Understand squawk codes, special codes (e.g. 7500, 7600, 7700), and code assignment. Know radar separation and the conditions for its use: identification, communication, and surveillance. Understand radar vectoring and the phraseology.
Navigation aids
Know the operating principles of VOR, DME, NDB, ILS and GNSS, and their limitations. Understand ADS-B and multilateration as modern surveillance. Know radar coverage and blind spots.
Traps and a rule of thumb
Traps: confusing Mode A (identity) with Mode C (altitude); forgetting that SSR requires a transponder; and assuming radar coverage is continuous. Rule of thumb: primary radar sees where, secondary radar asks who and how high. Worked example: an aircraft squawking 7700 is declaring an emergency - the controller must treat it as such and act accordingly.