A Welding Torch in Your ATU
Sometimes we forget that the RF running around in your ATU can be a really good welder!
Someone forgot to fully insert the J-Plug bar in this ATU input – perhaps after making an impedance measurement. The high resistance contact led to arcing, melting, and finally removal of enough metal to stop the arc! Meanwhile, enough power flowed that the transmitter VSWR overload didn’t see a thing.
This antenna tuning unit had 50,000 watts on it, but even 1,000 watts can make a mess under the right circumstances.Regular inspection of all RF systems is important. Coil clips, J-plugs, and other contacts should be checked for fit, discoloration and temperature (power off, please!). Take a walk around the antenna array more often. It will surprise you what you see!