An apparatus for an antenna assembly, which can be used for a mobile application such as on an aircraft, can include a housing defining an interior. A first antenna, such as a WAAS GPS antenna, can mount within the interior to operate at a first frequency. A second antenna, such as an L-band monopole antenna, can mount within the interior of the housing. A trap coupled to the second antenna can be tuned to the first frequency to prevent signal loss caused by the second antenna.