Your third-floor station has a ground wire running 10 metres down to a ground rod. You get an RF burn when you touch your HF transceiver while transmitting. What is the likely cause?

When working with High Frequency (HF) radio waves, a ground wire acts like an electrical circuit component rather than a simple drain. A 10-meter wire happens to be a significant fraction of a wavelength on several HF bands (such as a quarter-wavelength on the 40-meter band). When this happens, the wire acts like an antenna and presents high RF impedance. Instead of safely draining RF energy to the ground rod, it causes RF voltage to build up on the chassis of your transceiver, resulting in an RF burn when touched. Other options are incorrect because wire gauge and wall outlet grounds deal primarily with AC power safety, not RF voltages. Simply making an overly long wire thicker won't change its resonant properties.