Back in the 28.8kbps, 640 X 480 internet days an experimenter in Greece put up a nice web page about his junk box AM transmitter.
I stumbled upon it back then and found it really interesting, then it went 404 as all web pages from back then did when which-ever dial-up ISP folded.
Thanks to the Internet Archive, I was able to relocate this lost gem and offer it to you now. A teaser follows, the entire work is linked below:
Simple low power AM transmitter
Since many people are looking for low power radio transmitter plans, I’ve decided to post the plan of the most simple radio transmitter I know.
It is a little AM transmitter, a wireless microphone really, for the Medium Wave band (but it can be used for low power broadcast on the Short Wave band too).
What is attractive in this circuit is its simplicity.You can’t expect much from such a little project, but, it’s a good and especially easy start broadcasting.
It won't cost more than 5-10 USD, the components are everywhere readily available (or, they can be cannibalized from any old AM portable radio).
It can be constructed and tested in less than 2 hours. The transmitting power is subject to the transistor type one will use and the voltage of power supply, but it’s somewhere around 50mW, as far as I can tell.
I found that my construction works best on the 800-1200 kHz range, but with changes to the inductor or the variable capacitor it can transmit to the whole range of the AM dial.
Christos Z. Konstas
See the entire web page here: Simple low power AM transmitter