This spreadsheet puts Shannons Therom, Free Space Path Loss and thremal noise formula together to work out the theoretical maximum channel capacity (bits per scond) that can be squeezed through a communication channel given Frequency, Distance, Channel bandwith and transmit power. You can also enter total (transmit + receive) antenna gain.
This is the highest theoretical data rate you can get given the parameters - the actaul rate will be lower than this and will depend on coding efficency and channel noise (e.g. sky noise, front end and amplifier noise).
Enter data in the green cells - result in the yellow.
Play with the spreadsheet and see what difference the parameters make.
Remember - ya canna change the laws of physics.