Comparison of G/T between dual-reflector and primary-focus antennas

The paper presents results on comparisons of antenna gain and the sum of antenna temperature (G/T) for primary focus operations using either the single or two-mode feeds. It is noted that the Cassegrain operation of moderate-sized antennas at low frequencies often poses difficulties because of the large feed-horn required. Primary-focus operation using a two-hybrid-mode feed horn is shown to give a G/T ratio close to that provided by classical Cassegrain operation with a single-hybrid-mode feed.