COMTEK Stack 3 Yagi array switching systems allow an operator to select any single or any combination of three HF Yagi beam antennas. As compared to a single Yagi or a hard wired Yagi phasing system, these relay switching systems provide a greater range of signal arrival and transmission angles. They electronically combine the three equal-length 50 ohm feedlines from identical Yagi beam antennas without the use of special components or internal frequency dependent parts. These systems may be used to match and switch a 3-monoband Yagi stacked array for any HF band, 40, 30, 20, 17, 15, 12, and 10 meters. The consoles operate on 115 Vac. Three 1/4 wavelength cables, one made from 50 ohm and two made from 75 ohm coax, are connected to the Stack 3 relay unit to accomplish the impedance matching. These frequency-specific cables are sold separately. Instructions for building these cable assemblies are included in the manual. Comtek Stack 3 Yagi array switching systems feature a double-sided printed circuit board, Amphenol SO-239s, MOV protection for all six control cable lines, and they incorporate gold plated DPDT relays.