Radio hams reach for shooting stars By Bob Renshaw The bright light of a meteor is a result of heat produced by the meteorite entering the atmosphere. IN the last article we looked at communicating by bouncing a radio signal off the moon. This time we will look at using another space object to reflect radio signals - meteors. So what is a meteor and how can it reflect radio signals? A meteor is the streak of bright light that can be seen from Earth when a meteorite enters the atmosphere. The actual object entering the atmosphere is called a meteorite, and it is usually a piece of an asteroid. The term meteor refers only to the image created by this entry - a bright light cascading from the sky - often referred to as a falling star. The bright light of a meteor is a result of heat produced by the meteorite entering the atmosphere. The meteor is travelling at a very high speed. The molecules of air try to get out of the way but cannot and they pile up at the front of the meteor, creating very high pressure and heating the air until it produces a plasma trail. It is this trail that reflects the radio signal. SO how can you use a meteor trail to reflect radio signals from one part of Earth to another? In the accompanying diagram, Station A transmits a signal and it travels into the ionosphere where it is reflected off the meteor trail back down to Earth where it is received by Station B. This method of communication is very similar to moon bounce but in this case the whole contact takes only a second or five at most because the meteor trail lasts only a very short time. The equipment required for this type of operation is the same as moon bounce - a large antenna connected to an amplifier that makes the incoming signal stronger. In turn, this is connected to the radio which is connected to a computer which is used to process the signal. Due to the very short duration of the signal, software is used to produce, send, receive and decode the information sent by the other station. You can often hear such "pings" when they occur, and you will see them as spikes on the green line and brighter colours in the waterfall spectrum. The second diagram shows two contacts. You can see the spikes in the green line and the orange stripe in the waterfall. If you want to know more, or have an interest in amateur radio, you can find more information at www.radioclubs.net/c.a.r.s./ or www.facebook.com/CaithnessARS