Abstract A new configuration of sample and r.f.-coil for spin-echo NMR is presented. The main features are a homogeneous r.f. field over the whole surface of the sample and the possibility of calibration of the r.f.- amplitude in the presence of the magnetic material. In connection with Fourier-transformation of the echo-signals this allows for better accuracy in measurements of the NMR-enhancement factor, especially in broad spectra. The method is illustrated by an experiment with amorphous CoP, a ferromagnetic metal with a very broad spectrum.