Codan training course material which we use at our head quarters while training people how to use Codan Radio Equipment
Module Outline
Aim:
- To develop an understaning of how HF radio waves propogate and the effect it has on radio transmission
Objectives:
- Define three types of HF propagation
- Describe the different layers of the Ionosphere
- Describe 3 major Ionespheric conditions which effect propagation
Properties of Radio Waves:
- Waves travel in straight lines
- Waves will be “attenuated” or weakened if they pass through anything that conducts electricity
- The amount of attenuation (and therefore range) depends on frequency and what the wave must pass through
- Increasing power does not increase range in proportion
Radio Propagation:
- Propagation is the word used to describe the way in which radio waves travel from a source to a destination
There are three fundamental modes of propagation:
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- Direct Wave
- The radio wave travels from source to destination without interference
- Point to point as in space
- from ground to a relatively close aircraft
- Direct Wave
Range is short at ground level because the radio wave travels in a straight line and the earth is curved. VHF propagates in a similar manner.
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- Ground Wave
- When a direct wave runs parallel to the ground it will follow the ground contours
- It will be absorbed, depending on the moisture in the ground
- Ground Wave
A ground wave may be considered as bending around the curvature of the earth, but having quite a short range.
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- Sky Wave
- When a direct wave passes through the ionosphere it may be weaked by absorption and refracted (bent)
- Sky Wave
In some circumstances the bending is sharp enough to send the wave back down to earth far away from its source. In this case it is called a “sky wave”.
I dislike reading lengthy content, only as i’ve got some dislexia, but i really enjoyed this one