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Rough Science 4 Death Valley: Kathy Sykes' diary: Communication

Updated Tuesday, 29th August 2006

Kathy Sykes's diary about the challenge for the Communication programme, from the BBC/OU series Rough Science 4

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Kathy and Jon's talking sunbeam Copyrighted  image Icon Copyright: Production team

Day One

Jonathan and I have done something like this once before in Carriacou - we made a radio transmitter and receiver that meant we could communicate across a distance of a whole 15 metres. That is an easily shoutable distance. So we needed to do better than that, really!

To communicate across space it's just not possible to use sound waves. Sound relies on air as a medium so, since space is effectively a vacuum, no sounds can be heard. We can only hear on Earth because we exist in an atmosphere with air. So light is the obvious thing to use to try carrying a message, since it can travel across a vacuum without any problem. But we still need to capture the sound of a voice somehow on the light beam.

We had a small laser pointer, but frankly light from the sun here is so intense that it makes more sense to try and capture that somehow. Jonathan gets cannibalising an old radio to get hold of the transistors. They're sensitive to light, usefully. I make a load of light reflectors. Since we're not sure what we need or what will be most effective, I make lots to try out. Really have no idea which will work best.

It's a lovely idea - light carrying the vibrations of a voice, so you can pick it up somewhere else. Just detect the changes in the light, turn it all into an electrical signal, amplify then feed it to a loudspeaker. Sounds simple - perhaps too simple.

Day Two

We go off to the mine to try out what we have - the exposed light-sensitive transistors from the radio, the laser pointer and a multitude of different reflectors. It's deliciously, amazingly cool inside the mine. A blast of cold air comes racing at you just on opening the doors. It feels too good to be true in the heat of the desert! You can't believe it will keep blowing.

It takes AGES, just ages, to work out and to film. We do find that smaller tubes make the tin foil vibrate more. That may be good - we may need to maximise the response. But maybe we just need to use bigger reflectors - casting a light beam over a distance is harder than I'd imagined. Using a wider light beam may be necessary just to be able to see the damn thing to be able to line it all up. At least we've learned something and Jonathan's detector worked.

I tried out different options outside the mine - a bit of mirror stuck on a rubber diaphragm (a bit of old car tyre) compared with a tube with tin foil stretched over it. Jonathan tweaked his diodes, I played with my reflectors, then we set it all up outside - and it all felt quite promising. It actually worked. Everyone was delighted.

The challenge now is to make it work over a distance of more than 15 metres. In fact, Kate now tells us we have to get a signal across the length of the mine. Hmmm! Thanks, Kate!

Kathy and Jon's talking sunbeam Copyrighted  image Icon Copyright: Production team

Day Three

So a day to tweak and make the thing work over a decent distance.

I've found that a small bit of mirror is much, much better than tin foil. Just like in the solar oven, the tin foil (even when polished) has small kinks in that reflect the light all over the place. The mirror is such a good reflector, it means we 'lose' less light.

It turns out that 'losing' the light is our biggest issue. The small reflectors cast such a small light beam that even over only 15 metres we just lose them... we can't see them. The bigger reflectors are better, so even though the smaller tubes produced a bigger response it didn't matter because we couldn't ever 'find' the light beam.

As usual, at the start of the day we thought we'd get it all cracked reasonably easily ... but everything got predictably manic ... and the worst thing happened. It began clouding over and a storm started to brew. Even slight cloud cover affected our device.

It all went crazy, trying to get the plaque, the pen and the device - and all of us - all ready at the same time when the sun happened to shine was nearly impossible. And it was stretching our device to the limit, which made it all the more a joy for everything to work when the sun did shine. We were crazily excited. It just feels a bit magical to have made this thing. The pen worked upside down and Ian's plaque was a beauty.





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