The use of relays to improve the performance of wireless systems finds some limitations, which in the case of Amplify and Forward repeaters come from the need to decouple the incoming signal from its outgoing amplified version. In this paper we analyze the performance of Amplify and Forward relays for a partial overlap between the input and output frequency contents. By considering the relay as a Linearly Periodic Time Varying System we compute its transmission capacity, which depends strongly on the undesired coupling from the amplified output signal into the input antenna. As a byproduct, a fair comparison between half-duplex and full-duplex operation is obtained, complementing some initial results which can be found in the literature.