The receiver could be switched to either the belly antenna, or the DF loop. The choice of antenna was independant of frequency choice. She said she was receiving 7500 through the loop, but then adjusted the receiver to listen on 3105 or 6210. She might have switched antenna's at the same time, and not associated the loss of reception with the antenna change. Keep in mind that this would only affect her ability to hear the Itasca, not her ability to transmit. The silence after she said she was changing to 6210 is unexplained.