The ETS-Lindgren Model 3164 Series Diagonal Dual Polarized Horns include the 3164-03 and 3164-04 antennas. The Model 3164 Series was designed primarily for wireless communications test and measurement applications. Together the Model 3164-03 and Model 3164-04 cover the frequency range of 400 MHz to 6 GHz, with the 3164-03 covering the entire frequency range, and the 3164-04 operating between 700 MHz and 6 GHz. While intended as receive antennas, the Model 3164 Series also can be used as low power radiators, with a maximum continuous power handling capability of 200 W for the 3164-03, and 10 W for the 3164-04. The Model 3164 Series are precision machined from aluminum and polycarbonate. Two orthogonally-placed input connectors permit simultaneous measurements for horizontal and vertical polarizations for linearly polarized electromagnetic waves. By using an additional 90-degree hybrid phase shifter, the antennas may be used to transmit or receive circularly polarized electromagnetic waves. Tests show that the isolation level between the two orthogonal test ports in the specified operating frequency range is better than 25 dB for the 3164-03 and 20 dB for the 3164-04. The port isolation is the limiting factor in the cross-polarization levels of the antenna. When the Model 3164 Series antennas are installed in a free-space environment such as a rectangular shielded anechoic chamber, the Equipment Under Test (EUT) must be at a test distance meeting the far field requirements to operate either antenna within the full frequency range.