This is a picture taken from an old "Popular Electronics" Magazine featuring the schematics of the old Knight Kit Wireless AM Broadcaster circuit. I am currently in the process of obtaining all the parts to build one of my own. If you have any old 50C5's or 12AX7's laying around, feel free to send them my way! email@example.com
This is a new "twist" on the Phono Oscillator AM Transmitter that is available in kit form for about $40 from Antique Electronic Supply. The version below includes an audio preamp stage which is pretty much essential in order to get a good modulation ratio. You can probably scrape the parts together cheaper than if you were to buy this kit.
Here is the imfamous 6888 AM Broadcast transmitter which is enshrined at www.antiqueradios.com . They say it has better range and audio quality than the Li'l 7 transmitter or the AES kit. I will have to build one of these just to see how good this one really is. The guys on antiqueradios.com seem to love it.
Below is an aftermarket version schematic of the old Knight Kit AM Broadcaster, just in case you too would like to make one.
Here is another schematic of the previously mentioned 6888 transmitter. Mind the pin-out configuration on the crystal oscillator!
Another phono oscillator. Probably just as good as the Knight Kit, but uses cheaper parts. This is a plus for experimenters like me!