Part 66 AME Licence Syllabus - Radio Systems
What this domain tests
The Radio syllabus of the NZ Part 66 AME licence assesses the system-level knowledge needed to inspect, functionally test and certify radio communication, navigation and surveillance equipment on NZ-registered aircraft. Questions are practical: what the signal path is from LRU to antenna, which measurement proves the system is serviceable, and what defect makes it unairworthy.
Frequencies you must know cold
- VHF communications: 118.000–136.975 MHz, amplitude modulated, 25 kHz channel spacing in NZ.
- HF communications: 2–30 MHz, single sideband, for long-range oceanic work.
- VOR: 108.0–117.95 MHz; ILS localiser: 108.10–111.95 MHz (odd tenths); ILS glideslope: 328.6–335.4 MHz.
- DME: 960–1215 MHz; transponder: 1030 MHz interrogation uplink, 1090 MHz reply downlink.
- ELT: 406.025 MHz to the Cospas-Sarsat satellite system, plus 121.5 MHz for local homing.
Feedline, antenna and the VSWR measurement
Performance is proved by measuring forward and reflected power at the antenna end of the coax. The reflection coefficient is the square root of the power ratio; VSWR follows from it. A mismatch wastes transmitter power, can trip protection circuits and shows as a short-range comms fault.
Worked example
A VHF comm test set reads 50 W forward and 2 W reflected. Reflection coefficient = square root of (2/50) = 0.20. VSWR = (1 + 0.20)/(1 − 0.20) = 1.5:1. Return loss = −20 log(0.20) = 14 dB. Power actually delivered to the antenna is 48 W, less coax loss. A 1.5:1 result is acceptable; 3:1 or worse demands investigation of the antenna, connector or bonding.
Traps that cost marks
- Forgetting the square root: 2/50 = 0.04 is the power ratio, not the reflection coefficient.
- Confusing return loss sign conventions, or forgetting that 2:1 VSWR means about 11% of the power is reflected.
- Mixing the transponder's selected code with the Mode C altitude reply.
- Quoting DME slant range as if it were ground distance.
- Reversing localiser (lateral) and glideslope (vertical) guidance.