In this paper the subject of inter-sensor coupling in antenna arrays and its effect on source-localization performance is addressed. A new approach for direct calculation of the port noise covariance matrix in antenna arrays is presented. The proposed approach is based on applying the theory of noisy linear networks in antenna arrays using the method of moments (MoM) impedance matrix to account for the noise mutual coupling between the array elements. The noise model considers both the external noise sources from sky, ground and interference and internal noise sources from amplifiers and loads. The theory is demonstrated in the source localization performance analysis of a vector-sensor antenna array, and of a newly presented two orthogonal loop vector wire antenna. It is shown that the noise coupling in antenna arrays may substantially alter the behavior of the array and should be taken into account in the design process and in the performance evaluation of the array.