Beemaster, that's a 10,000 watt station, the same power as the one I worked at and the first one I messed with the towers on. At night, they probably drop it to 1,000 watts as WMOX was required to do. A 1KW station is a baby one. At WMOX, the transmitter was between 50 and 100 yards from one of 4 towers, in a concrete block building. There was enough rf that 2 of the computers had to be shielded or they would randomly do strange things or lock up.
Screw threads ... yeah, it doesn't seem right, but nature is strange sometimes ... threads make contact with the ball, then you slowly push the tip towards the other ball. The arc happens just before the tip contacts. As long as you have fairly clean surfaces and you hold the threads firmly to the ball, it'll act just like in the video... maybe a spark or two but that's it. If you actually touch the screw tip to the second ball, it'll weld and probably then burn the threads enough to arc and maybe weld. ... sorta like a welder .. you hardly ever see a spark at the ground clamp teeth unless you stick the rod and have a bad connection at the clamp .. or the clamp slips off while you're working a stuck rod loose.
WMOX is a talk station now... When I was there, they still played music and only did a morning and afternoon local talk show... then Rush Limbaugh started up.
... the big daddy AM stations in the US are 50KW