Aircraft scatter is about bouncing our VHF/UHF radio signals off high-flying aircraft – ‘hitching a ride’ with someone else’s plane to extend our everyday working range out to 700-800km. This sounds rather technical, but aircraft scatter is actually very easy; here in NW Europe there are so many planes in the sky that aircraft scatter just happens, even when we’re not aware of it. For example, if you are one of the hundreds who get involved in the monthly UK Activity Contests on 2m, 70cm and 23cm, you will already be using aircraft scatter routinely and it will be responsible for some of your best QSOs.

So how does aircraft scatter actually work – and if it’s so useful, why haven’t we heard more about it?

Ian’s talk will explain how signals are reflected from aircraft, and which parts of the aircraft are likely to be the most helpful. Much of this has been known since the early days of radar, more than 80 years ago; but for communication we also need something else. We need lots of planes in the sky, flying routes that will scatter our signals forward to useful destinations. The enormous growth of aircraft traffic that accidentally transformed aircraft scatter into an everyday propagation mode has only taken place in the past 30-40 years.

Signal paths come and go as aircraft move across the sky, so the next big step is to take more deliberate advantage of the paths that are available. Notice that beaming along the major air traffic corridors will also link us into areas of high population where we are more likely to find QSOs. Thanks to plane-spotters and their online ‘virtual radars’, detailed air traffic information is now available in near-real time – in fact far more detail than we need. So finally for this evening we’ll take a brief look at software like AirScout, that specifically supports our amateur radio hitch-hiking activities and allows us to plan scheduled contacts… but that’s a topic for another time.

=========================