02 Communication Methods Flashcards
The VHF Spectrum?
The radio frequency spectrum is part of the electromagnetic spectrum. The VHF spectrum spans all the frequencies from 30 to 300 MHz
The air band range?
The air band is the range of VHF frequencies spanning 108-137 MHz.
Location of the HF band?
The HF frequency band sits below VHF. The UHF frequency band sits above the VHF band in the radio spectrum.
The minimum seperation between frequencies in the air band?
The minimum separation between useable frequencies in the air band is 8.33 kHz.
This used to be 25kHz
If you don’t have 8.33 radio, you should say ‘negative 8.33’
Uses of VHF?
VHF radio, VDF, VOR, Marker Becon and ILS
The four factors which reduce the effective range and quality of VHF radio transmissions ar
- Line of sight requirement.
- Curvature of the Earth.
- Atmospheric electromagnetic interference.
- Power of the transmitter.
Frequency bands?
Frequency ranges increase by a factor of 10.
How to remember EM spectrum?
Very
Lovely
Maidens
Have
Very
Useful
Sewing
Bands
Air-ground communication?
Two-way communication.
Air-to-ground communication?
One-way communication
Equation for Wavelength?
c = λF
c = 3 x 10^8
Blind transmission?
A transmission where two-way communication cannot be established but where it is believed that the called station can receive.
Broadcast?
A transmission not addressed to a specific station or stations.
Duplex?
Communication which can take place in both directions simultaneously
Ground-to-air communication.
One-way communication
Interpilot air-to-air communication?
Two-way communication between aircraft.
Non-network communications?
Radiotelephony communications outside the normal lines of a radiotelephony network?
Radiotelephony network?
Radiotelephony network. A group of radiotelephony aeronautical stations
Readback?
A procedure whereby the receiving station repeats a received message.
Simplex?
Communication takes place in one direction at a time.
Air/Ground Radio?
Not run by qualified personel.
Telecommunication?
Any transmission, emission, or reception of signs, signals, writing, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems.”
Modulation used for VHF?
AM modulated
Identifying AC modualtion issues?
Carrier wave + voice = full RT heard
Carrier wave + no info = static noise heard.
If you just hear a click, or static, this means just the carrier is being transmited, no modulation is occuring.
What frequencies are more likly to be effected by static and noise?
The lower the frequency the more likly to be effected by static and noise.
How is radio range effected?
Transmit power
R~sqrt(Power)
Doubling the range needs 4 times the power
Super refraction?
Inversions can create a ducting to allow the passesage of energy.
VHF range increases substantially beyond the LOS
Attenuation?
The loss of energy.
What increases attenuation?
- Higher frequencies / shorter wavelength
- Increased air density / decreased temperature.
Therefore least attenuation occurs between aircraft at higher frequencies.
Phase differnece?
A phase differnece can cause fading of a signal.
Max Theoretical Range Equation?
Max Theoretical Range (nm) = 1.23 (sqrt(Tx)+sqrt(Rx))
Tx = the elevation of the transmitter (feet AMSL)
Rx = the elevation of the reciever (feet AMSL)
