Simple. The first 5 minutes out of each hour, the satellite goes "deaf".twolf816 said:and how would the satellites know you are testing and "disregard signals during this time period"?
how in the world if you turn it on for 2 sec is someone gonna know where it came from?
Those satellites are very precise. It can pinpoint your location in a matter of seconds, so don't dick around!
121.5 is, as stated, a guard frequency. You hear all the time, an ATC trying to reach an aircraft on it that isn't answering on their usual channel. The best way to describe it is as an Emergency/Calling/Distress frequency. Just the same as 156.800.