Introduction: Build a Computer Controlled Radio Transmitter
This will allow you to send morse code through radio waves to another computer. This could be used as a sort of chat program.
Step 1: Gather Supplies
You will need very few supplies:
-A crystal oscillator (will talk about which kind in the next step)
-A 9 pin serial jack (D-SUB9)
-A little bit of wire
-Something to use as an antenna
-A male to male audio jack (unless you know morse code)
Step 2: Which Oscillator?
To determine what kind of oscillator you want you will need to know what kind of radio you have.
Regular AM/FM radio - We will be using only the AM part. The numbers on the dial are frequencies in KHz. Most oscillators are marked in MHz. You will probally want something in the .3MHz(300KHz)-1.5MHz(1500KHz) range.
Shortwave radio - Go with whatever frequency your SW radio can play. My radio has 3 bands. One is a KC (KHz or AM) band and the others are MC (MHz). I use a 20MHz oscillator.
Step 3: Wire Some Stuff Up
You will need to solder a wire onto pin 4 of the serial jack. This one should be red to make it easier to work with later but not nessesary.
You will also need to solder a (black) wire to pin 5 of the serial jack.
Step 4: Wire Up the Oscillator
Take the red wire (from pin 4) and connect it to the pin directly above the black dot on the oscillator. Next, take the black wire (from pin 5) and connect it to the pin to the right of the black dot.
Step 5: Add Antenna
Now add an antenna to the pin opposite the black dot. You can use pretty much any insulated wire as an antenna, just as long as it isn't too thick. I used a 25 foot telephone wire.
Step 6: Send Some Morse Code
Download the morse code program (linked below).
Connect the serial jack into your computer.
Type some stuff in.
Click the radio menu on the top.
-You may have to choose a different COM port from the "Com Port" menu.
-If your using a SW radio you can select the CW setting by clicking the radio menu and selecting CW
Your radio is now transmitting.
Step 7: Receive Some Morse Code
There are to ways to do this.
-Learn morse code
-Use a computer: Find a radio.Tune to your freqency. Use a male to male headphone plug to connect the headphones part of the radio to the microphone jack in the computer. Download and install cwget.zip. When running it SHOULD (doesn't work well for me) start to decifer the morse code. Read the manual to figure out how.
Step 8: Congrats
Your all done.
A few tips:
-Get a good antenna. I heard about someone who did this with a 24.3MHz oscillator and a 10 meter antenna and sent his signal from California to Texas. I haven't tried testing mine outside my house yet, but it works pretty well here.
-Get a higher frequency oscillator if possible. If you have a SW radio then you can to this, otherwise stick with AM. If you use AM though be warned that your messages won't be private. Anyone can pick up an AM signal.
-Check your frequency. If your frequency is in an amatuer radio range then you will need a licence to run it. If it is in an AM range, you can only send your signal a few blocks (I think it's a mile) without a licence.
Hope you can use this to send secret messages to far away friends.