7 October – Aircraft Scatter, the Hitch-Hikers Guide by Ian White, GM3SEK

| October 8, 2024

The presentation

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 north-west 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 explains 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, and 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 to 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 in far more detail than we need.

So finally 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.

About Ian

Ian was licensed in 1963, and somewhat by accident found himself on the VHF bands.

In his bedsit years in London, he operated in portable contests with various groups, and in the meantime was continuously building and improving his own equipment such as transverters, power amplifiers and antennas.

Settling in South Oxfordshire, he could begin to try some advanced VHF/UHF propagation modes, first meteor-scatter and eventually moonbounce.

The 1970s-80s were golden years for technical developments, and in order to consolidate this new knowledge, Ian and a group of friends pooled their expertise to write The VHF/UHF DX Book which is still a valuable resource today.

As a professional technical author and editor, for 17 years Ian wrote the In Practice column in RadCom, every month answering a range of technical questions from readers.

This obliged him to take an interest in a very wide range of amateur radio topics, and a side-effect was that his own list of new things to try began to grow again.

On retirement in 2005, moving to south-west Scotland offered the chance to build a good HF station, and the challenge to develop a new set of operating skills.

With DXCC Honor Roll on 40m CW plainly in sight but unreachable, he is now mostly retired from HF DX chasing, but he still enjoys DX and contest operating on 6m, 2m and 70cm “to keep the tools sharp”.

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