Abstract: An electromagnetic response from a region in an earth formation is determined by lowering an electromagnetic measurement tool into a borehole in the earth formation. The tool comprises a transmitter antenna, a receiver antenna, and an electrically conductive support structure. The transmitter antenna is energized, resulting in receiver signal in the receiver antenna. A raw response signal, comprising the receiver signal, is measured at the receiver antenna. The raw response signal is adjusted using a reference signal obtained by measuring the response signal of the tool in a test environment having a resistivity that is higher than that of the region in the earth formation. This method can be employed during the drilling of the borehole which may be part of a method of producing a mineral hydrocarbon fluid.