hello
the trick is farily simple...
at the beginning of your init() function you can add a couple of instruction to change the PWM frequency (see atmega8 datasheet) then conect an IR diode between the PWM pin and a regular pin that you're going to use to transmit data. the anode of the diode is connected to the data pin and the pwm pin will be connected to the cathode.
set the pwm duty cycle to 50% (127)
this trick allows you to send data modulated at whatever frequency is produced by the pwm without having to code complex assembler loops...
massimo