Rockwell Collins 718U 5M avionics HF SSB transceiver built into a professional desk-top rack

This is the Rockwell Collins 718U-5M avionics SSB radio installation (for HF bands), built into a desk-top rack as a fully operational HF radio setup. The equipment covers 2 MHz to 30 MHz in 100 Hz synthesized steps. Any frequency can be selected within that range, there are no lockouts. Frequency selection is done freely through toggle switches for each frequency digit, or by selecting one of the eight memory channels. These memories are user-programmable and non-volatile. they 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") that is built like a Swiss time piece. The tuner can match any antenna from the proverbial coat hanger to long wire antennas. But it also tunes perfectly into standard 50 ohms coaxial cable. Automatic antenna impedance matching is done by means of two motorized vacuum capacitors and one motorized inductor. Antenna 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 (single tone modulation), 14 amps average (during voice). When receiving, the installation draws about 2 to 3 amperes. The 718U-5M consists of following sub systems: -671U-4A receiver/exciter, military designation RT-1443/ARC-174(V) -548S-3a amplifier/coupler, military designation AM-7202/ARC-174(V) -514A-7 control unit, military designation C11289/ARC-174(V) -990C-3 mounting (for receiver/exciter) -990C-5 mounting (for amplifier/coupler)