This needs no power supply. It is operated only by the voice power.
http://www.intio.or.jp/jf10zl/PLTX.htm
1MHz CW signal is oscillated by feedback oscillator. And this signal is modulated by audio oscillator. Radio frequency is changed by 1500pF. Audio frequency is changed by 0.022uF
http://www.intio.or.jp/jf10zl/a2tx.htm
This circuit is deliberately limited in power output but will provide amplitude modulation (AM) of voice over the medium wave band.
http://www.zen22142.zen.co.uk/Circuits/rf/amtx.htm
74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration
http://ourworld.compuserve.com/homepages/Bill_Bowden/page6.htm#amtrans.gif
W0HIO has this neat old 40m AM rack that is ready to be restored. Lots of interesting pictures.
http://www.qsl.net/ab0cw/30srack_tx.htm