Well, pulse, usually to hear a transmission, there must first be a radio set to receive the transmission. Unless I'm mistaken (and I may very well be; forge world is friggin huge!) there isn't a radio in an abandoned base or crashed ship that would pick up a transmission. Unless, of course, there are forgeable radio sets that pick up the signal; or if your spartan's comm unit can actually receive the transmission. In that case, I would try spawning a radio (or just standing; I can't remember if there is a forgeable radio) at the highest point on the map. Now that I think of it, most of the human vehicles would most likely have a radio.
Congratulations, you got me to thinking.
