Technical data

ASTi Telestra 4 Training Manual (Ver. 1, Rev. F)

• Frequency Hopping – a method of rapidly switching frequencies while a receiver and

transmitter communicate. The receiver and transmitter have to jump between the same

frequencies, at the same speed, and at the same time.

• Crypto Parameters – radios that scramble the signals before they are transmitted so

that only receivers who know the special key will have the ability to decode them, pro-

ducing a secure voice transmission across any frequency.

• Half Duplex and Full Duplex – Half-duplex mode is when the radio is able to transmit and

receive signals but cannot do both at the same time. Full-duplex allows radios to transmit

and receive signals at the same time. Typically, full duplex is only used for intercom sys-

tems and never for real radios.

• Propagation – the movement of the radio waves as they transmit.

• Ranging – is an effect that occurs as a result of the distance between two radios. The

greater the distance between the radios, the weaker the signal due to the dissipating

power of the signal as it traverses a large area.

• Occulting – the loss of radio signal due to the curvature of the earth’s horizon.

• Ionosphere Effects – the loss of signal due to the changes in the earth’s atmosphere

such as time of day or different seasons. The ionosphere effects only occur with High

Frequency (HF) radios.

• Line of Sight (LOS) – when radio waves traveling in a straight line are dispersed due to

obstacles or obstructions.

• Fresnel Diffraction – loss of signal due to the reflection off obstacles in the path of the

radio waves from transmitter to receiver.

• Terrain Effects – the loss of signal due to land obstruction such as a mountain.