When I was in the army I used to get called SandAmerican Inventor a lot because I am half Iranian (but not the I'm-going-to-blow-you-the-fuck-up kind, I promise). It was kind of racist, but I also thought it was pretty funny and so it stuck. So for radio communications we all had a preferred callsign. And since occasionally high ranking officers and NCOs would listen in on radio chatter; "SandAmerican Inventor" obviously wouldn't fly. So "Sandman" was coined as the radio-friendly version.
You add the word "actual" to the end of your callsign if you are frequently sharing your radio with a squad or team member, that way if you yourself speak on the radio you refer to yourself as '[callsign] actual', and if someone else in your team or squad uses the radio they refer to themselves as just '[callsign]'.
I don't claim to be a macho cool military special forces guy, either. I just did a quick six years and got out. Did it for the experience, the discipline and met some cool people along the way. That's it.
I loved the callsign when I was in though. I use it as my handle for almost every non-RPG game now.