The AM radio test not only confirms the 121.5 transmission, but is also a valid test for the integrity of the common antenna. I'm not suggesting that this be done on purpose of course, but if the unit was accidentally triggered for an extended short period, sometime other than the allowed "5 min. after the hour" test period, you should soon receive a phone call and can admit to an accidental triggering event. It happens, and I understand that they are usually very nice & understanding about it. That would be a valid "test" of the transmission to the satellites.