Slashdot Mirror

The Xtal Set Society: http://www.midnightscience.com/

I learned electronics starting as a young kid when i obtained one of those "150-in-1" (or 100-in-one or 200-in-1) kits with an assortment of components on a board with spring connectors, to which you run wires according to directions in the manual. The one i had (probably Radio Shack) had cartoon characters of electron characters that explained the theory behind the circuitry you were wiring up. No need to solder, no need to dig through parts bins, but great for learning the theory behind a variety of circuit types (alarms, radios, high voltage generators, etc.).

There are tons of these type kits out there - as well as kits to build individual devices (also great learning experiences, and you wind up with a useful piece of equipment) - check the links at http://www.lutins.org/lists/electronics.html If you *are* thinking of building a single-device kit, i highly recommend the Midnight Science Ultra-RX1, an ultrasonic listening device available from http://www.midnightscience.com/ultra-kits.html. The kit is built in three sections, with instructions on how to do some troubleshooting-type testing after each section. When you're done, you'll have a device that allows you to listen in on ultrasonic emanations (bugs, bats, etc.) - mine works *way* better than i ever expected!

This was originally going to be a quick reply to someone talking about CB, but I haven't seen HD addressed nor the advantages of analog decoding/receiving, so here goes...

The problem with CB is that CB isn't installed in everyone's car and walkman. This is like fighting Microsoft by dumping into the ocean every copy of Microsoft Office -- for Macintosh.

Having the FCC reserve a swath of AM bandwidth for citizen broadcasts is a much better idea. Lots of open space during the day, inexpensive and very simple to construct transmitters, and you can listen to the broadcasts using radios that don't require power. And, surprisingly, 95% of drivers can listen with the radios they've already got installed in their cars. That's democracy-building (or whatever kind of society you're trying to construct).

That's also what concerns me with 'High Definition' (HD), aka digital, radio. Will we displace analog broadcast? Will we be able to continue building radios that work for free -- rather, will those radios have a signal they can decode in 70 years, or will we be digitally bound? Don't DRM my AM, please. This is a simple technology found in 95% of cars and I'd daresay 99.99% of homes (and anyone with a dime store and $5) that can pick up broadcasts from hundreds of miles away. For the sake of shoving bucks to radio manufacturers, giving a little extra income for the gov't, and a few new stations, we're willing to throw that network away. Bad news. Let them eat UHF.

How do you stop the currently fatalistic drive to HD, when every group with lobbying power (incl. the gov't) is in on the take? This is a hard sell for your typical voter, as the replies of what's generally an above-averagely tech savvy group like /. to this thread show we're not exactly well-informed about the tech behind radio. Is there really an advantage to not just consumer but citizen in moving to digital setups? I'm not sure there is.

There are a ton of crystal-radio projects here:

http://www.midnightscience.com/

I remember listening to alot of static. I couldn't get many frequencies in my area.

You do not need batteries to make a radio reciever. You should try building a crystal radio sometime. You can receive AM radio without battery or external power. The whole thing is powered by the antenna.

I have never actually heard about a SC ruling like that, but that's how it SHOULD be. If someone is generating an EM field, and it passes through my property or person, I should be able to do whatever the hell I want with it. If the signal provider doesn't like it, they are free to add more and more complex protection to the data in the signal. Or, they can pay for a bigass Faraday cage that I can put around my place.

It's already illegal to monitor certain radio frequencies... cell phones and cordless phones for example. Building a receiver from a handful of basic components can make you a felon. It's crazy. Crazy. Service providers should protect their data with technology, not new laws.

Side note: even though I am a ham and I am fairly clued in on electronics, I find it AMAZING on some level that crystal radios work. There is enough juice flowing through you RIGHT NOW to DRIVE AN EARPHONE with NO POWER SUPPLY in the circuit. Doing the math is one thing... building a passive circuit that produces sound is something else. Wacky.

Actually you don't need a magnent (really ferrite bar). An oatmeal cylindar box and wire will do.
Here are some links to some crystal radio pages:

http://www.freeweb.pdq.net/headst rong/foxhole.HTM The razorblade radio plans
http://www.midnightscience.com/
http://www.freeweb.pdq.net/headst rong/crystal.htm
http://www.thebest.net/wuggy/
http://home.earthlink.net/~drduggee/xt al.htm