It is no surprise that GPS/GNSS [Global Positioning System/ Global Navigation Satellite System] is remarkably important in modern society, with applications ranging from mobile phones to missile guidance systems. Particularly in the military, these signals can often dictate the difference between life and death. Therefore, modernization of GPS equipment and techniques has been a natural process following years of technological advancements in RF technology. One of the main achievements in this field was the development of M-codes, which provide a more reliable, secure, and flexible GPS source for military receivers. M-codes can improve GPS applications in the military – let’s look at the role software-defined radios (SDRs) play in this industry.