Bruce,and Michael, You can use any Pic micro with a pwm output to generate modulated serial data. I have been doing it for about 2 years since I started using 16F88's for remote controls. All you need are 2 diodes with there anodes connected 1 to the tx output and 1 to the pwm output and the cathodes driving a pnp transistor for the IR drive... Try it...

Dave Purola,
N8NTA