3-7
Figure 3-6.—Rf amplifier unit.
POWER SUPPLIES.—One power supply produces operating voltages for the amplifier when
operating from a 60-hertz power source. All components of the power supply, except the power
transformers, are mounted on a chassis and panel assembly that is hinge-mounted to a metal case. The
power transformers are constructed as part of the case and there are no operating controls.
The other power supply produces operating voltages for the rf amplifier when a 400-hertz, three-
phase, 115-volt primary power source is used.
ANTENNA COUPLER GROUP.—The antenna coupler group is an automatic antenna tuning
system. However, the equipment design includes provisions for manual or semiautomatic tuning. This
makes the system adaptable for use with other radio transmitters. The manual tuning capability is useful
when a failure occurs in the automatic tuning circuitry. Tuning can also be accomplished without the use
of rf power (SILENT TUNING). This method is useful in installations where radio silence must be
maintained except for brief transmission periods.
The antenna coupler matches the impedance of a 15-, 25-, 28-, or 35-foot whip antenna to a 50-ohm
transmission line at any frequency in the 2- to 30-megahertz range. Control signals from the associated
antenna coupler control unit automatically tune the matching network in less than five seconds. During
manual and silent operation, tuning is accomplished by the operator with the controls mounted on the
antenna coupler control unit. A low power (not to exceed 250 watts) cw signal is required for tuning.
Once tuned, the coupler is capable of handling 1,000 watts peak envelope power (pep).
The coupler is enclosed in an aluminum, airtight, pressurized case. Six mounting feet enable the unit
to be attached to the mast of a ship at the base of a whip antenna. The coupler is pressurized with dry
nitrogen to aid internal heat transfer and to prevent corona and arcing. All components of the coupler are
secured to a chassis that is mounted to the case so that an air duct exists between the chassis plate and the
