About 15 years ago when I was still a member of the Anne Arundel radio club where I got my novict ticket, a friend of mine found an old 4Mhz sspark gap transmitter and wanted to try it out on field day. So when he immediately keyed it up heblew the 7500 volt transformer putting the small of Davidsonville in the dark for 3 hours. 73- pat kk3f