The present invention relates to a portable directional antenna which is equipped with a camera which is integrated into the housing of the directional antenna. In addition to the conventional documentation of the position-finding information, this integrated, installed camera makes it possible, by means of the directional antenna function, to also optically document the surroundings of the interference source with a variable level of detail, for example by way long-range or short-range capture. By way of the optical additional information thus obtained, the present invention provides a simple, but nonetheless very effective, enhanced documentation option for interference sources and the surroundings thereof. Thus, during the search for radio-frequency interferences, no separate camera for capturing image information has to be brought along, and this increases the comfort for a user. The present invention further relates to a portable measurement arrangement and to a method for measuring an electromagnetic si
