Rockwell Collins 718U-5M avionics HF SSB transceiver (AN/ARC-174)

This is the Rockwell Collins 718U-5M avionics radio installation (for HF bands), in fully operational setup. The radio covers 2 MHz to 30 MHz in 100 Hz synthesized steps. Frequency selection is done through toggle switches for each frequency digit. The radio allows for 9 user programmable non-volatile memory channels, which also store modulation mode. Programming can be done from the front control without restrictions. The radio has a built-in automatic antenna tuner (Collins calls it a "coupler") which tunes anything from the proverbial coat hanger to long wire antennas. Tuning is done by means of two motorized vacuum capacitors and one motorized inductor. Tuning time is about one second on average, 2 seconds maximum. Re-tuning is done once the operator changes the selected frequency. The radio has two audio inputs, one for a carbon microphone (or carbon simulating like the Telex 66T), and the other a 600 ohm balanced input for digital modems. Audio output impedance is 600 ohms with enough power to drive a 600 ohm communication speaker. Required supply voltage is 28V DC at 22 amps peak (two tone modulation), 14 amps average (speech). During receive the installation draws about 3 amperes. The 718U-5M consists of following sub systems: -671U-4A receiver/exciter -548S-3 amplifier/coupler -514A-7 control unit, military designation C11289/ARC-174 -990C-3D mounting (for receiver/exciter) -990C-2 mounting (for amplifier/coupler)