Page 207 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 12: Space-based Wireless WANs

MS to be viable propagation mode especially during times of little or no propagation modes such Notes
as, as far as 6M is concerned, F2 ES, TEP or Aurora.
Figure 12.8: Diagram of Meteor Scatter

Source: http://jt6m.org/meteor-scatter.php
Meteor Scatter as shown in figure 12.8 allows propagation of up to 2500km during peak meteor
shower activity and using “random” meteors, can provide qso’s at almost any time of the day
and year. Results can be quite spectacular at times and at other times very disappointing. Signals
are usually very weak and of short duration.

So what is Meteor Scatter ?

As meteors fall into the earths atmosphere - commonly known as “shooting stars”, ionisation
occurs typically in the E layer and acts as a reflector for vhf signal . Meteors typically are small
pieces of debris left by a passing comet but can also be small pieces of matter floating around
space or even pieces of man-made space junk falling back into the atmosphere.
Cometry debris can be as small as a grain of sand and cause ionisation to occur. Small pieces
of debris usually burn up completely as they pass into the atmosphere but larger pieces can
partially ionise and the remainder falling to earth, known as “meteorites”. The meteor trails
which typically occur at altitudes between about 80 and 120 km can be effectively used to reflect
radio signals.
Meteor scatter activity can use either annual meteor showers or random meteors. Meteor
showers are experienced at specific times during the year, the number of meteors entering the
atmosphere rising significantly as the Earth’s path passes through debris in its orbit around the
Sun. Some of these have been traced back to the passage of a comet. The number of visible trails
rise significantly during some of the larger meteor showers, the Perseids shower in August is
probably the best.
Meteor showers appear to originate form a point in the sky which is termed as their radiant. The
radiant usually identified by the name of the constellation or major star in the area of the sky
from which they appear to originate, and this name is usually given to the shower itself.
Random Meteors

The majority of meteors entering the atmosphere are random meteors. These are the space debris
that is within our solar system. Unlike the meteor showers they enter in all directions and they
do not have a radiant.

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