High Frequency (HF) Communications Flashcards
Aviation High Frequency (HF) communications provide the pilot the ability to:
communicate with controllers or home stations from thousands of miles away
HF operates using what waves?
Sky Waves which allows worldwide communications
In general, HF comm’s transmit using:
the Single Side Band (SSB) mode of operation
Single Sideband is the preferred method of transmission because:
the narrow bandwidth works better for Sky Wave propagation
Most systems switched to which mode?
Amplitude Modulated (AM) mode
A typical HF control head includes:
a frequency selector, a squelch or RF gain control, and a mode control switch
All but the data mode is used for:
voice communication
The data mode is used for digital type information that is:
linked to equipment external of the HF radio system
(ACARS)
The data communication system is known as:
Air - Ground Data Link or Data Link
HF Comms are long distance communication systems and are not:
employed on all aircraft
The wavelength for 3 MHz is:
100 meters
The wavelength for 30 MHz is:
10 meters
If a transmitter is connected to an antenna of inappropriate length, the antenna impedance will not match the transmission line. This will cause losses because of:
Standing Waves
After changing frequencies, the pilot momentarily keys the HF transmitter. The antenna coupler uses the energy from the transmitter to measure:
the standing waves generated by the antenna length that are not appropriate for the frequency used.
The Antenna Coupler will add capacitance or inductance as needed to eliminate:
standing waves, allowing maximum power transfer between the antenna and HF system.
