Dan,

That has nothing to do with this Thread, "RF communications..."!!
Be sure to start a new thread, otherwise nobody will see your new question if it's disguised as a reply to a completely irrelevant topic!

With Keil, the C51 compiler converts your .c Source file(s) to .obj Object file(s);
you must pass your .obj Object file(s) to the Linker to create an absolute file;
you can pass your absolute file to the BIN2HEX utility to create a Hex file.
This is all fairly normal practice.

The Keil uVision environment gives you a GUI to "simplify" the process.