Ground is good.
Or bad, depending on your need…
This is Tower 2 of a 4 tower AM array, a 207’ self supporting AM Tower is situated in a marsh area of the NJ Meadowlands.
The station runs 50 kW day and 7.2 kW night, into a 4 tower array. All of a sudden one day, the array went out of tolerance.
A star ground was installed under this old tower to stabilize the ground reference due to fluctuating tides on the marsh property the station is located on.
The radial wires were installed years ago. Certainly prior to the last paint job which looks rather old.
Unfortunately a couple of them were threaded through the base insulator of one of the tower legs.
At some point one of the wires brushed up against the bottom of the insulator.
Over time the insulation broke down and it ultimately shorted the tower to ground, throwing the antenna array out of tolerance.
Lightning may have been involved since the wire was spot welded to the nut when I arrived.
As I arrived on the scene to help troubleshoot this problem, I measured 10 ohms on this tower with a hot impedance bridge.
Knowing the tower was grounded by something that shouldn’t be there, I located this wire and kicked it to see if it would twitch.
During this time, the station was running 12.5 kW into one of the other towers in the array. That RF energy was
being coupled into this tower which was floating at the time. The wire instantly sparked and the insulation caught fire.
A substantial amount of RF juice is being routed to ground through this tower out of thin air.
Yes, that nut on the bottom of the insulator is connected to the tower above.
It continued to arc and sizzle with modulation…
With the offending wire snipped out of the way, the station returned to normal
operation, blasting the area with 50 kW of solid state AM programming