Motorola GM360 Specifications download pdf (Page 31)

Radio wave propagation illustrated

The following illustrations show the characteristics of ground-wave and sky-wave

propagation during day

and night time. In each

illustration the height of

the ionosphere above the

ground is shown. For

radio transmissions to

travel greater distances,

multiple hops (deflections

by radio signal from the

ionosphere to earth) are

repeated.

In both illustrations

Station A communicates

with Stations B, C and D.

Propagation from Station

A to B is by ground-wave.

The diagrams illustrate

that the time of day and

the height of the ionosphere above the ground do not affect the ground wave.

Day

The sun is higher, the best frequency to use is higher A to B –

Possible optimum working frequency is 3MHz. A to C – Possible

optimum working frequency is between 7 – 9MHz. A to D –

Possible optimum working frequency is between 13 – 16MHz

Propagation from Station A to C and D, however, is by sky-wave and as the diagrams

illustrate the sky wave is

significantly affected by

the time of day and the

height of the ionosphere

above the ground.

Below

Night

The sun is lower, the best frequency to use is lower A to B –

Possible optimum working frequency is 3MHz. A to C – Possible

optimum working frequency is between 5 to 7MHz. A to D –

Possible optimum working frequency is between 9 to 12MHz

each diagram

there are recommended

working frequencies

listed. These will vary

according to time of

year and other factors

such as the type of

antenna used. They are

intended only as a guide

and are subject to

change.

Radio Operators Training Manual Version 27/11/2007 29

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Motorola GM360 Specifications Page 31

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