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Meteor Scatter Propagation & Frequencies

Meteor Scatter Propagation & Frequencies

The way in which meteor scatter radio propagation can be used depends upon the characteristics.

Meteor burst communications is dependent on frequency, and there are a variety of issues that affect the frequencies that are used - not all depend upon the characteristics of the meteor trails and their effects on the signals.

Meteor scatter frequencies

In common with other types of radio signal propagation, meteor scatter is frequency dependent. Reflected power levels as well as the burst duration are both affected by the frequency used. The levels of power returned reduce significantly with increasing frequency, as does the effective duration of the trail. As a result the maximum limit for meteor scatter operation is generally around 150 MHz, although some very dense trails have been known to affect frequencies as high as 500 MHz.

For the commercial systems that use the under dense trails the maximum frequency is somewhat lower, and the communications are often limited to a maximum frequency of about 50 MHz. Typically most operation takes place between about 40 and 50 MHz, although operation on lower frequencies would be possible. Below 30 MHz interference levels rise as a result of the increased number of signals resulting from ionospheric propagation.

Meteor scatter & Doppler shift

When using meteor scatter or meteor burst communications it is found that the signals that are received are subject to a Doppler shift. This arises because the point where the signal is reflected changes as the meteor moves forwards and new ionisation is created, and the trail behind it diffuses. This can give a shift in frequency of as much as 2 kHz on the higher frequency bands although it is correspondingly lower for the lower frequency bands.

Signal paths for meteor scatter

Meteor scatter or meteor burst communication is able to support communication up to distances of around 2000 km. There is also a minimum distance that exists. This arises because the meteor trails are only able to reflect signals over small angle. Shorter distances required the signals to leave the transmitter antenna at a higher angle and therefore a much higher angle of reflection is needed. This factor limits the minimum range to about 500 km. The optimum distance is around 1000 km.

Meteor scatter / burst overview

Meteor scatter or meteor burst communications is an interesting form of radio communications that can be used for medium data rate signals at the low end of the VHF spectrum. It is used occasionally for commercial data applications where real time communications are not required. A link is set up that looks for signal propagation via a meteor trail and when one is available the data is transmitted using this. The link remains dormant until the next one is detected. These links use the under dense trails. For ham radio applications most operation takes place during the periods of meteor showers. When signals can be heard, high speed Morse is normally used to transmit the required information.

Watch the video: Meteor scatter magic MSK144 on VHF (November 2020).