It's not easy to build a high-power narrow-band AM transmitter, let along a broadband one. The issue is the long wavelength makes aerial matching difficult (at

It's not easy to build a high-power narrow-band AM transmitter, let along a broadband one. The issue is the long wavelength makes aerial matching difficult (at 1MHz the wavelength is 300 metres, i.e. speed of light/frequency). AM transmitters for national use generally run 10's to 100's of kilowatts of power [0], and longwave is even higher, e.g. UK Radio 4 is 500 kilowatts. Pretty unlikely to build a high-power one by accident :) [0] http://www.mediumwaveradio.com/uk.php http://www.mediumwaveradio.com/uk.php