If you're looking for a very easy and affordable, learn-while-you-build project to get into low power radio, this might be a fun little romp. John does a very nice job in his project write up titled:
A comprehensive story containing technical elements & personal opinions
by John Fuhring
John shares with us his insights into 'The Four Noble Truths of AM radio as it exists today' then takes us through a nice discussion of 'Buy or build your AM transmitter?'
After that it's into the 'Technical section' where we learn about how this transmitter works and get right into building and operation. Based on the Hartely oscillator design made popular by Charles Wenzel and simplified by Mr. Fuhring for easy construction, this little analog sweetheart is similar to one of my first efforts way back in the early 90s.
Mine was built from a schematic found in the Ernie Wilson / James Cunningham effort (sorry, it's a huge 4.3 MB PDF, might take a while to load, don't bother unless you are browsing at 5 mbps and up) and, as a testimony to my poor construction techniques, seemed to work best at 790 KHz even though I was using a 1 MHz crystal in my oscillator section.
The unit in this plan is a VCO but this approach has been proven quite stable thanks to the buffered output and those meaty toroidals. This looks like a great hands on AM transmitter project with oodles of theory, a nice plan to work from and a reasonable expectation of success.
Complete, informative and loads of fun, when combined with a good ground, a properly matched antenna and good modulation, this approach can provide much low power broadcasting entertainment!
There is a very ineresting 'Easter egg' on John's site about what really delayed rescue when the Titanic went down - check it out!
For a look at some additional approaches to building a simple AM transmitter, be sure to visit