[Corvettaholic]

OK, I had just had a fantastic idea, which is only useful for the coolness factor. Lets take one of my local radio stations KUPD, which is trasmitted at 97.9 Mhz. Lets take an AM radio station of 800 Khz. Still can hear both just fine, lets disregard quality for a moment. The important thing here, is that even with such a range of frequency, these stations can still broadcast through things like walls with varying degrees of success. My idea is to broadcast using a REALLY high frequency. Time to leave the radio spectrum, scoot past the microwave spectrum, and its time for infrared! Which I was informed IS heat. So I'm wondering, if someone used a heat lamp for an antenna, as opposed to a long piece of wire, could you pulse infrared radiation? Sure a heat lamp won't work well because it probably can't pulse like that, at least not at a perceptible level. My reasoning is that radio waves aren't exactly perceptible either, until received, translated, and amplified. So why not make a simple crystal radio thats tuned for the infrared spectrum? I know it won't broadcast through anything, but thats not the point.

You're thoughts on this guys?

[Scratch-]

Just buy an infrared LED (light emitting diode) from radio shack for about $1.50. A lot of things use infrared like your remote control for TV/stereo/VCR and wireless connections for PDAs and laptops for example. The only problem is that the higher the frequency the less it goes around objects, so you need a line of sight. But the upside about higher frequency is that you can pulse things faster without the wave breaking up, meaning faster data transfer (fiber optics are better than radio).

[Mitch]

I don't think this is a very practical idea, good luck with it. As, Scratch said IR will only work through a line of sight and probably not very far.

[Corvettaholic]

I'm too concerned with practicality on this one. The only thing I want to do is send a message about 10 feet away in a direct line of sight, and i'll be happy. I know IR is used for a ton of things, but I'm looking at using something that puts out a lot more energy than a LED, such as a fire or a heatlamp, lightbulb even. If I pulse power to a lightbulb, will that give me a usable IR transmission? Something like pulsing voltage to an antenna for a simple crystal radio?

[Scratch-]

Just use 40 LEDs, it will transmit a lot better than something that’s not made to carry a signal. A single LED will reach 10 feet if the circuitry is configured properly.

[Corvettaholic]

Well I'm not worried about how good of a transmitter it is, I WANT to use something that wasn't meant to carry a signal. If this works, next project is to send a signal by having a flappy-thing make waves in a pool of water.

[Donaldson Tan]

might as well use the lamp to transmit information via morse code.

some sort of light sensor can record the the morse code light signal and a computer program can read the morse code from the light signals

think any hobby electronic shop will sell the light sensor. just need to wire it to the computer and write some C++ program to read the data input and display the interpretation on the VDU.

I m thinking along the line of using ultrasonic frequency for communication. after-all, our ears cant listen beyond 20khz, but think the soundcan travel quite far. Perhaps some sort of ultrasonic broadcast and listener device

[Corvettaholic]

Doesn't sound travel a lot better underwater? I like the idea of an ultrasonic transmitter. Maybe I could set up something in Tempe Town Lake? Its this little man-made lake in the middle of the freaking desert, not too deep, so it'd be perfect for underwater transmission experiments!

[jdurg]

Sound does travel better underwater due to the fact that the molecules of water are a LOT closer together than the molecules are in air.  As a result, the sound is transmitted much better.  Any dense gas or material will transfer sound a lot better, and a lot louder, than normal air will.  An example of this is a CO₂ filled ballon.  If you've ever popped a balloon that was filled with carbon dioxide, you'll know just how much louder the "pop" is.  If you're not careful, it can cause serious damage to your ears.  Also, if you've seen enough movies, you'll notice how when people are underwater the bad guys will just randomly throw grenades into the water.  That's because the exploding grenade will be sooooooooooooooooo much louder than it would be in the air.  This can cause disorientation and damage to the person they're trying to "get."  

[Corvettaholic]

So just to be clever, I COULD run a water filled hose from a big speaker in the house, to a big thingy outside and blast a lot of sound? I know using a simple speaker cable and outside speaker would be a whole lot smarter... but I could do it the other way? This sounds a lot more fun that using heat as a signal.

[jdurg]

The sound level won't be any different outside since the speaker will be outputting the sound into the air.  The only way you'd notice a difference would be if you went and submerged yourself underwater as well as the speaker.  

[Corvettaholic]

Well then, into the water I go! Come to think of it, I do remember as a kid when I sat on the bottom of the pool and big people jumped in, it made a really loud sound! Suppose I don't actually need to play with this idea too much.