NCAA Aeronautical Station Operator cheat sheet

Aeronautical stations are licensed under national telecommunications law implementing ITU Radio Regulations; the station licence names the licensee, call sign, frequencies, power, class of emission, and operating hours.

The ITU Radio Regulations divide aeronautical services into aeronautical mobile (OR and R), aeronautical fixed, aeronautical radionavigation, and aeronautical radionavigation-satellite services; each has distinct frequency allocations.

Aeronautical mobile (R) service uses frequencies reserved for safety and regularity of flight; aeronautical mobile (OR) service covers other communications, mainly ground operations.

ICAO Annex 10 Volume I sets equipment and operational standards for aeronautical communications; Volume II covers radiotelephony procedures; Volume III covers communication systems.

A station licence is not transferable without authority approval; changes to frequency, power, location, or antenna require licence amendment before operation.

Operators must hold a valid certificate of proficiency or licence appropriate to the station class; the certificate states privileges and must be available for inspection at the station.

The station licence and current frequency assignment records must be kept at the station and produced on demand to an authorised inspector.

International operation requires the aircraft or station to carry the appropriate radio licence and operator certificates recognised under bilateral or ITU arrangements.

Radio Regulations Article 18 requires stations to be operated by qualified persons; Article 19 requires stations to identify by call sign at specified intervals.

Frequency f, wavelength λ, and speed of light c relate as λ = c / f; with c ≈ 3 × 10^8 m/s, a 118 MHz VHF signal has λ ≈ 2.54 m.

Modulation types: AM (amplitude modulation) varies carrier amplitude; FM varies frequency; SSB suppresses the carrier and one sideband, saving power and bandwidth.

In AM, the total power P_total = P_carrier (1 + m^2/2), where m is modulation index; 100% modulation doubles total power relative to carrier.

Receiver sensitivity is the minimum input signal producing a specified output; selectivity is the ability to reject adjacent-channel signals; both depend on IF filter design.

The decibel is a logarithmic ratio: dB = 10 log10(P1/P2) for power, 20 log10(V1/V2) for voltage; +3 dB doubles power, +10 dB multiplies power by 10.

Free-space path loss in dB is FSPL = 32.44 + 20 log10(d_km) + 20 log10(f_MHz); doubling distance adds about 6 dB loss.

Impedance matching maximises power transfer; a 50-ohm transmitter feeding a 50-ohm antenna with a 1:1 VSWR delivers full forward power with no reflected power.

VSWR relates to reflection coefficient Γ by VSWR = (1 + |Γ|)/(1 − |Γ|); a VSWR of 2:1 corresponds to about 11% reflected power.

Noise figure and receiver bandwidth determine noise floor: noise power P_n = kTB, so doubling bandwidth increases noise power by 3 dB.

VHF aeronautical communications (118–137 MHz) propagate mainly by line of sight; usable range is approximately 1.23 × √h for a single antenna height h in feet, or radio horizon = 4.12 √h_metres km.

Ground-to-air VHF range is the sum of the aircraft and ground radio horizons; at 10,000 ft aircraft altitude and a 100 ft ground antenna, range is roughly 140 nautical miles.

HF (3–30 MHz) supports long-range communications via skywave refraction in the ionosphere; daytime D-layer absorption is high, favouring higher HF frequencies by day and lower by night.

The ionospheric F2 layer provides the greatest skywave skip distances; the critical frequency is the highest frequency reflected vertically from a layer.

A half-wave dipole has a feed-point impedance near 73 ohms and gain of about 2.15 dBi; a quarter-wave vertical over a ground plane has about 36 ohms and 5.15 dBi when the ground plane is ideal.

Antenna gain and directivity are related; a directional antenna concentrates power, increasing effective radiated power in the favoured direction without increasing transmitter power.

Coaxial cable loss increases with frequency and length; use low-loss cable and short runs on VHF to preserve transmitter power and receiver sensitivity.

Polarisation: VHF aeronautical communications use vertical polarisation; mismatched polarisation between transmit and receive antennas introduces additional loss.

Standing waves on a feedline indicate impedance mismatch; reflected power reduces radiated power and can damage the transmitter if excessive.

VHF air-ground channels use 25 kHz or 8.33 kHz channel spacing; 8.33 kHz spacing is mandatory in designated European airspace above specified flight levels.

The 8.33 kHz channel designator is not the actual frequency; the designator is derived from the channel frequency, and the actual carrier is offset by 1.25 kHz or 2.5 kHz from the designator.

Aeronautical fixed service links use HF, VHF, UHF, or satellite bearers to carry AFTN, ATS, and meteorological data between ground stations.

Transmitter keying must not cause interference on adjacent channels; check the channel is clear before transmitting and release the key promptly after the message.

Squelch circuits mute receiver audio when no carrier is present; excessive squelch may block weak signals, so set squelch just above the noise floor.

Emergency frequencies: VHF 121.5 MHz and UHF 243.0 MHz are guarded for distress; HF 2182 kHz and 4125/6215 kHz are used for maritime and aeronautical distress.

Equipment tests must use a dummy load or approved test frequency to avoid radiation; never test on an operational channel without coordination.

Antenna selection and transmitter power should be the minimum necessary for reliable communication to reduce interference and conserve spectrum.

Standard call sign format: aircraft identification followed by the ground station name; the ground station responds with the aircraft call sign.

Read-back is mandatory for runway clearance, hold-short instructions, altitude assignments, and any safety-critical instruction; the controller must verify the read-back.

The word 'ROGER' means the message was received; 'WILCO' means received and will comply; 'AFFIRM' means yes; 'NEGATIVE' means no.

Phonetic alphabet: Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu.

Numbers are transmitted digit by digit, except whole hundreds and thousands which may be spoken as 'one hundred' or 'two thousand'; altitudes use 'feet' unless otherwise specified.

Frequency transfer: the controller states the next frequency; the pilot reads it back and confirms when established on the new frequency.

The word 'I SAY AGAIN' requests repetition; 'SAY AGAIN' is used to request repetition of all or part of a message.

Time is transmitted in UTC as four digits, e.g., 'one two three zero' for 12:30 UTC; date groups use six digits, day-month-year.

When two stations transmit simultaneously, the controller may say 'STANDBY' or 'BLOCKED'; the pilot should wait and retransmit when the channel is clear.

AFTN messages have a priority indicator: SS (flight safety), DD (urgent), FF (flight regularity), GG (general), and KK (administrative); SS messages receive the highest handling priority.

AFTN message format begins with the priority indicator, destination address, originator address, and date-time group, followed by the message text and ending signal.

The date-time group is six digits: day of month, hour, and minute in UTC, e.g., 121530 for the 12th at 15:30 UTC.

AFTN addresses are eight-letter location indicators; the first four letters identify the station, the next three the department, and the last letter the service.

A message is not considered delivered until acknowledged; AFTN uses positive acknowledgement and retransmission for undelivered messages.

Message correction: use 'COR' before the corrected text; cancellation uses 'CANCEL' with the original message reference.

The originator is responsible for message content; the operator must not alter the text except to correct transmission errors, which must be identified.

AFTN messages must be checked for completeness of address, priority, and date-time group before transmission; incomplete messages are returned to originator.

NOTAM is a notice distributed by means of telecommunication containing information concerning the establishment, condition, or change of any aeronautical facility, service, procedure, or hazard.

NOTAM classes: NOTAMN (new), NOTAMR (replace), NOTAMC (cancel); each carries a serial number, location indicator, and effective period.

A NOTAM is issued for information of immediate operational significance; it must be concise and use ICAO abbreviations where standard.

METAR is a routine aviation weather report issued at fixed intervals; SPECI is a special report issued when significant weather changes occur.

TAF is a terminal aerodrome forecast; it covers a specified period and includes wind, visibility, weather, clouds, and expected changes.

Weather reports use ICAO abbreviations: wind direction and speed in degrees and knots, visibility in metres, cloud height in hundreds of feet, temperature in degrees Celsius.

SIGMET is a warning of hazardous weather such as thunderstorms, turbulence, icing, or volcanic ash; it is issued for the safety of aircraft operations.

A NOTAM must be checked before flight; pilots and operators are responsible for reviewing current NOTAMs relevant to the route and aerodrome.

Distress signal is MAYDAY (spoken three times); urgency signal is PAN PAN (spoken three times); safety signal is SECURITE (spoken three times).

Distress call format: MAYDAY, MAYDAY, MAYDAY, station addressed, call sign, position, nature of distress, assistance required, intentions.

The distress frequency for VHF is 121.5 MHz; for HF, 2182 kHz and 4125/6215 kHz; UHF 243.0 MHz is also guarded.

The distress message has absolute priority over all other communications; all stations must cease transmissions that may interfere.

Urgency communications concern the safety of an aircraft or person but do not require immediate assistance; they use PAN PAN and have priority over routine traffic.

Safety communications contain important navigational or meteorological warnings; they use SECURITE and are broadcast on appropriate frequencies.

Silence periods: on HF, silence periods of three minutes are observed at 15 and 45 minutes past each hour on 2182 kHz and 500 kHz (where applicable) for distress watch.

When a distress message is heard, the station must acknowledge if it can assist, or remain silent if another station has acknowledged and is handling the distress.

The distress alert via satellite or digital means must be followed by a distress message on radiotelephony if possible.

A station log must record the date, time in UTC, frequency, call signs, and a summary of communications, including distress and urgency traffic.

Watchkeeping: aeronautical stations maintain a continuous listening watch on the distress frequency 121.5 MHz and on assigned operational channels during published hours.

Interference reporting: record the frequency, time, nature of interference, and any identifying details; report to the appropriate authority.

The station operator must not transmit on a frequency unless authorised and must identify with the station call sign at the beginning and end of communications.

Logs must be retained for a period specified by the licensing authority, typically at least one year, and made available for inspection.

When interference is encountered, the operator should first check own equipment, then coordinate with affected stations, and if unresolved, notify the regulator.

Emergency power and backup communications must be tested periodically and maintained in operable condition.

The operator must maintain a current list of frequencies, call signs, and operational contacts for the station and adjacent facilities.