The very first electronics circuit I ever built, an audio amplifier, turned out to be sensitive to the local AM radio station, WJOB, 1230 Khz. When I took it to

The very first electronics circuit I ever built, an audio amplifier, turned out to be sensitive to the local AM radio station, WJOB, 1230 Khz. When I took it to school to show my teacher... the building shielded the signal, and it didn't work. 8( Only later did I learn why it happened, and how to prevent it.