A method for upgrading a dual-band antenna assembly to a tri-band antenna assembly is provided. The dual-band antenna system includes a main reflector, a strut assembly coupled to the main reflector defining an antenna feed receiving area spaced from the main reflector, and a subreflector carried by the strut assembly and also spaced from the main reflector. The subreflector includes a frequency selective surface (FSS) material that is reflective for both a first frequency band and a second frequency band and transmissive for a third frequency band. First and second antenna feeds are arranged in a coaxial relationship adjacent the main reflector and directed toward the subreflector. The first and second antenna feeds are for first and second frequency bands, respectively. The method includes positioning a third antenna feed at the antenna feed receiving area and directed towards the subreflector and the main reflector. The third antenna feed is for the third frequency band.