These automatic tuners are suitable for coax or endfed antennas. The tuners are weatherproof and suitable for outdoor use. The max. transmit power is 300, 600 or 1500W, depending on model. All tuners tune antennas over the entire shortwave range from 1.8 to 30MHz. The time to tune is max. 15 seconds, but usually as low as 5 seconds, because once found settings are stored in one of 10000 permanent memories.
The MFJ tuners works automatically, no manual tuning required. The tuning starts with a transmit power as low as 2 Watt (MFJ004BRT, other models require 5W), but 10 to 20 Watt are recommended for best results. The max. power while tuning should not exceed 20 Watt. Although the tuner is equipped with heavy duty 16A/1000V relays, they might be damaged when tuning at higher powers. The switched L network of the tuners allows up to 192 different L and 192 different C values, resulting in an impedance matching range of 12 to 800 Ω with the MFJ-994BRT, and 12 to 1600 Ω with the models MFJ-993BRT and MFJ-998RT.
These models are housed in a weatherproof outdoor box. The power supply is done over the coax feed, for that purpose a Bias-T MFJ-4117 is included in shipment. All tuners have PL sockets for the transceiver and the antenna, alternatively a wire post can be used for end-fed wires. For parallel wire fed antennas an external balun is required (not included).