Meteor Scatter 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. A brief description of Meteor scatter follows.

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 defined thus :

Meteor showers

These 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.

Meteor Trails

Meteors enter the earth's atmosphere at speeds between 10 and 80 Kilometres per second and burn up due to friction at altitudes between 80 and 120km, dependent on their size, speed and angle of entry. As the meteors burn up their atoms vaporise leaving a trial of positive and negative electrons. The trial formed is typically only a few metres wide but can be over 20km long.

Meteor trial can be divided in to 2 types depending on the density of the electrons. These are known as over dense and under dense.

Over dense trials produce relatively strong signal reflections. With a high electron density signals do not totally enter these trails and are reflected. The duration can be several seconds and are the result of larger sized meteors.

Under dense trails are formed by very small meteors, typically the size of a grain of sand. With a lower electron density these act in different way to over dense trails. A signal penetrates the trail and is scattered rather than being reflected. Only a small amount of signal is returned to earth, the signal typically rising in strength for a few hundred milliseconds and then decays but can last for a few seconds.

Signals are subject to Doppler shift but are less affected at lower vhf frequencies, 4M and 6M, but can be as much as 2kHz on high frequencies.