HF radio frequency range?
What is HF Max Useable Frequency?
Optimum frequency for best clarity (first returning sky wave) is reduced so that the receiver does not move in and out of dead space as ionospheric conditions fluctuate
When do HF MUFs vary most and why? How to remember?
Day and night because the ionosphere is less dense at night so less likely to retract as much Lower frequencies used at night to compensate Sun’s up, frequency’s up
What is civil VHF comms frequency range?
118-137 MHz Negligible interference from static tied with minimal atmospheric attenuation
What isn’t EHF suitable for radio comms?
Atmospheric attenuation significantly reduces range above UHF
What is fading?
Space waves and ground reflected waves move in and out of phase with each other to alternately reinforce and cancel each other out
How does ground direction finding (VDF) work?
Receiver aerial (Adcock) is a series of dipoles arranges in a circle. Each receives a slightly different phase of the signal and phase difference indicates where the signal is coming from
QTE = How to remember?
True bearing from station (true emanation)
QDR = How to remember?
Magnetic bearing from station Direction Radial
QDM = How to remember?
Magnetic bearing to station Direction magnetic (direction to because a radial is direction from)
True bearing to station
VDF bearing accuracy Class A= Class B = Class C= Class D =
2 degrees 5 degrees 10 degrees > 10 degrees
What is a VDF letdown? Is procedure chart available?
Pilot provided with QDM on each call so headings can be set for airfield overhead. Once overhead the published outbound track is flown followed by a turn inbound to land Yes
What is QGH? Is procedure chart available?
Ground homing - all work done by controller who passes headings to steer and descent instructions to pilot Procedures not published and no chart required