K54283 K54284
HF Communications System Component Location 5E6
23-11-02 Figure 1 (Sheet 1) Feb 20/87
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5E6 HF Communication Systems Component Location
Feb 20/87 Figure 1 (Sheet 2) 23-11-02
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
3. HF Transceiver
A. The transceiver is located in the electronic equipment rack E-2. Electrical connection is made to the rear panel and antenna connection is made to the receiver adapter mounting base front panel.
B. A blower motor provides forced air cooling for the transceiver components.
C. The transceiver panel contains:
(1)
LRU FAIL indicator - an LED that comes on when there are transceiver faults.
(2)
KEY INTERLOCK indicator - A LED that is activated when there are antenna coupler faults.
(3)
CONTROL INPUT FAIL indicator - An LED that is activated when there are control faults.
(4)
SQL/LAMP TEST pushbutton - Squelch disable and lamp test.
(5)
PHONE jack - A plug-in for a 600-ohm headset to monitor test audio.
(6)
MIC jack - A plug-in for a carbon microphone to enable voice modulation tests at the transceiver.
5E6
23-11-02 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 20/87
4. Antenna Coupler
A. The antenna coupler is located at approximately station 1016 just below the HF antenna vertical fin leading edge. The coupler has miniaturized transistor circuits contained in a rack-mounted pressurized case. Electrical connection is provided through two multipin connectors located on the front of the unit. The RF connection is through a coaxial plug designated RF INPUT located on the front panel. The antenna connection is at the rear of the unit.
B. The pressurized case has two sections divided by an RF shield which provides thermal protection as well as RF isolation. The forward compartment contains tuning control modules, a dual servo-amplifier, and the power supplies. Integrated circuit construction is used in the servo-amplifier and tuning control modules. The rear section of the coupler (the RF compartment) contains the tuning element, a discriminator module, and an isolation amplifier. The tuning elements consist of two variable vacuum capacitors and a variable inductor, associated motors, gear trains, switches, and RF relays.
C. Protection circuits in the coupler function to open the transceiver key interlock and remove RF power from the servo-amplifier circuits when any one of the following occurs: The coupler fails to home within 15 seconds. The coupler fails to tune within 15 seconds. An arc is detected in the coupler.
5. Antenna
A. The HF communication system transmits and receives through a flush-mounted shunt-type antenna. The antenna is located in the vertical fin leading edge. The antenna dielectric portion is constructed of fiberglass. The antenna is the metal leading edge of the vertical fin.
B. The antenna conductor, which is located at a low impedance point in the circuit, acts as a type of inductive coupling so that the airframe operates as an antenna.
6. Operation (Fig. 2)
A. Internal transmitter excitation and receiver injection frequencies are generated by a dual-loop phase-locked digital synthesizer. The transmitter output is nominally 400 watts peak envelope power (pep) with a maximum average power of 125 watts. The transceiver has a dual-conversion receiver that produces 200-mW received voice audio and 0.5-volt SELCAL audio outputs, and a 200-mW sidetone audio output. Operating voltages are produced by internal power supplies that operate from a 3-phase, 115-volt, 400-Hz primary source.
5E6
Feb 20/87 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 23-11-02 Page 5
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