Long distance communication

How far can you communicate in real-time without using direct electrical means?

You make up the methods, machinery, speed criteria, climatic conditions under which you expect to work. Take a method and once you have a working version try to extend the distance using relays if necessary. I'm not really thinking of one-shot bangs and flashes, but some means of maintaining a CHANNEL of communication.


A Heliograph is simply a mirror that reflects the sun. The sender moves the reflected spot of sunlight back and forth across the receiver. The receiver sees flashes of reflected sunlight. Make these long and short and you have a morse code message. Well can you get this to work over the distance of half a mile? (Don't use binoculars with the heliograph.)

At night time, how strong does a torch need to be to shine over a mile? You'll probably find it difficult to shine accurately in a given direction, and much easier to use binoculars and the qualities of the human eye rather than specialise too much at the sending end.

OK then is a bright pinprick easier to see than a gently illuminated sheet or balloon. Can colours, directional bars, or patterns be distinguished at night?

Topics for investigation

I'm sure you'll have fun trying out ideas and making them better in various ways. If there's a lot of feedback on this then perhaps I'll set up a workshop page so designs and problems can be shared.

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