Ratel Flashcards
What does a transponder do?
Enables a ground base radar controller or a pilot with an ACAS to determine the location (and altitude) of an aircraft
What is an ACAS
Airbourne Collision Avoidance System. fitted to another AC
How does a transponder work
a signal sent from a ground based rader unit is received by the transponder (interrogates the transponder). the signal triggers the transponder to send a coded signal back to the radar unit
sound waves travel at what speed
the speed of sound
what factor influences the speed of sound
air temperature
what is the definition of frequency
the rate of recurrence of a vibration, an oscillation or a cycle (past a given point)
how is wave motion described
by its shape and frequency
how do radiowaves (electromagnetic waves) differ from sound waves
- variations in the strength of electric and magnetic fields, which do not require a medium
- radiowave distances are substantially greater
- rw travel at the speed of light
how can the characteristics of a waveband be defined
wavelength, frequency, amplitude, frequency bands
what is wavelength
length of a single wave or one completed cycle
what is frequency
number of completed waves passing a point in one second
what is amplitude
distance from the top or bottom of the wave to the mean value line of a wave
why do we use the VHF band for aeronautical comms?
- large number of freuqncies
- reception is superior
what is a disadvantage of VHF band for aeronautical comms
inability of signals to bend around obstacles. line of sight
why would you be able to get a hf signal if you were in the lee of a mountain
sky waves- the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere
what is a transceiver
a receiver and a transmitter
what are the types of modulation and whats the difference
amplitude modulation- varying the amplitude while frequency remains constant
frequency modulation- vice versa
what are the advantages of fm modulation over am
clearer signals
greater availability of channels within a given range of frequencies
all ac in nz are fitted with 2 radios. what are they
transponder, elt
what is mode
a
c
a- four figure code (predetermined for a class of ac, issued to you by control, permanent discrete code issued) c- four figure code plus altitude
transponder codes off sby on alt test
off- off
sby- transponder switched on but will not reply to interrogations
on-will reply to interrogations but will send mode A only
alt- transponder on, will reply. Mode A and C will be sent
Test- test function
transponder codes
7500
7600
7700
7500- unlawful interference/ hijacking
7600- communications failure
7700- emergency- distress
2 major disadvantages of hf
static interference and signal fading
sound waves passing through air consists of …. being compressed and expanded; they move at the speed of ….
air, speed of sound
radio waves are …. waves; they move at the speed of …
electromagnetic, light
amplitude means the distance between
- top of wave to the bottom of the wave or
- top or bottom of the wave to the mean value line
top or bottom of the wave to the mean value line
what is meant by the term attenuation
weakening or decaying
when radio waves are in the vhf band they have a longer/shorter wavelengths than in the lf band
shorter
the preferred frequency band in aviation is ….
vhf
what is mean by the term transceiver
transmitter/receiver
what is meant by the term nav/com
combined radio installation for navigation aids and communications
what is an important negative aspect of vhf transmission/reception
comparatively short range, line of sight
flying higher/lower will improve range of vhf reception
higher
range of vhf reception in nz has been improved by the installation of
repeater stations
what is meant by the term modulation
superimposing of intelligence on the carrier wave
when you press the microphone transmit button, the radio transmits the … and when you speak into the microphone you add … to it
carrier wave, modulation
what happens if you activate your transmitter when another station is transmitting
you cut out other transmitions
what is the function of the squelch control
to control the level of unwanted signals or static
list two important steps before you transmit a message
formulate the message, listen for others
compared to normal conversation what should be your rate of speech during transmitting
slightly slower, conversational
what is the predominant advantage of hf over vhf and what is the predominant disadvantage
greater range. presence of static and fading
when you see a short 50-80cm antenna, what frequency band is the radio likely to operate in
vhf
after engine start you should select …. on your transponder and select …. or ….. for in flight conditions
sby, on, alt
when you turn the transponder function switch on, the equipment transmits mode ….. information which does/does not include altitude information
mode a, does not
when you are instructed to squawk ident you should
press the transponder ident button once
