A transmission device includes a coupler configured to convert a transmit signal to transmitted guided electromagnetic waves that propagate along a surface of a transmission medium without requiring an electrical return path, the coupler further configured to convert to a receive signal, received guided electromagnetic waves that propagate along the surface of the transmission medium without requiring an electrical return path. A housing is configured to provide environmental protection to the coupler. The housing includes an aperture section configured to pass the transmitted guided electromagnetic waves from the coupler through an aperture side of the housing, the aperture section further configured to pass the received guided electromagnetic waves to the coupler through the aperture side of the housing. The housing also includes a non-aperture section configured to absorb radio frequency (RF) signals in a frequency range of the transmit signal and a frequency range the receive signal.