Simple radio transmitter question

I am interested in building a small low powered radio transmitter. Searching the Instructables website I found some Instructables that have some with oscillators:

• Build a very simple AM Transmitter
• Make Your Own Low-Power AM Radio Transmitter

Some other projects are built with timer chips and transistors:

• 555 AM Transmitter
• Easy AM Transmitter!

Would someone please explain the theory or science, and advantages or disadvantages of the components involved when building each project? Thank you very much.

Comments

[steveastrouk]

The crystal ones will be nicely stable, the 555 ones will likely drift. The crystal ones can't be tuned, the 555 ones can.....

[rickharris]

The theory of radio is fairly simple:

An oscillator produces a carrier wave at the required frequency. this carrier wave is modulated by your signal, on off for Morse code, varying amplitude for AM modulation, Changing frequency for FM modulation.

The signal is received and the modulation decoded back to audio.

Making it work is really not that simple :-) BUT given time you can build a successful low powered TX RX set up.

[rickharris]

What is your long tern goal as this effects the method you use.

A simple spark gap can be used to transmit Morse code for example, this was the first radio transmitter, a similar tuned cct and spark gap was the receiver.

If your just interested try building several you will get some good experience AND learn a lot.

NOTE - transmitting is governed by Federal laws so be warned you may upset official people.

[blkhawk]

Thank you. It is duly noted.