Radiation susceptibility test circuit
People have come to me, requesting assistance in modifying their PCBs, often with failure in the 400-600MHz region. My response was "See that long PCB trace running from the MCU to the sensorIC? Its a quarter-wave at 400MHz, over Er=4 PCB material, unloaded at one end, loaded at the other (quarter-wave transformer---bad news, high voltages generated). Install a 10Kohm near the sensorIC."

The sensor IC was getting upset, via its SPI output pins.

With 10Kohms installed, to dampen RF energy and to mostly prevent RFI entrance to the sensor IC, the project moved ahead.

I suggest you specifically test at frequencies where the top/bottom traces will store-energy, as quarter-wave or halfwave striplines.

I also like the nasty-sparky NormallyClosed power-relay test idea.