3D1X3 Self Test Questions Vol. 3 Unit 1

Front 1

State the types of traffic an AN/TRC–170 radio terminal set might handle.

Back 1

Dedicated traffic such as analog and digital channels, point-to-point circuits, facsimile circuits, and teletype
circuits.

Front 2

st the equipment included in an AN/TRC–170 tropospheric scatter terminal.

Back 2

Antennas, transmitting and receiving equipment, digital multiplexing equipment, voice and data orderwire
facilities, built-in test equipment, and communications security equipment.

Front 3

List the data rates processed by the tropospheric scatter modem.

Back 3

Mission traffic at 128 through 4,096 Kbps in the 512 data rate family, and 72 through 4,608 Kbps in the
576 data rate family.

Front 4

Describe the upconversion process of the transmit amplifier.

Back 4

The IF signal is upconverted in the transmit amplifier converter by mixing it with a local oscillator input
from the synthesizers. The difference frequency is selected as the final transmit frequency of 4.4 to 5.0
GHz.

Front 5

Explain the difference in the transmission power requirements between tropospheric scatter and
line-of-sight.

Back 5

The HPA is necessary for transmission in the tropospheric scatter mode (1 kW, 60 dBm). It is also possible
to transmit in LOS mode by not using the klystron. The output is 29 dBm (800 mW).

Front 6

What is the minimum spacing used to separate receive antennas in space diversity, and what is the
most common amount of antenna separation used?

Back 6

Minimum of 50 wavelengths; common receive antenna spacing is 100 or more wavelengths.

Front 7

What principle of propagation does frequency diversity use to its advantage?

Back 7

Frequency diversity uses the principle that two different microwave frequencies fade independently of each
other even though they travel the same propagation path.

Front 8

What is the ideal frequency separation in frequency diversity?

Back 8

A separation of 5 percent is ideal.

Front 9

Define polarization diversity.

Back 9

In polarization diversity, the same frequency radiates simultaneously in two different planes: horizontal and
vertical.

Front 10

Explain quadruple diversity.

Back 10

Quadruple diversity is a technique that employs a combination of two or more of the diversity types: a
combination of frequency and space diversity or space and polarization diversity—or a system that uses
four reception paths.

Front 11

Explain the purpose of the digital data group modem.

Back 11

It interfaces up to four groups of conditioned diphase signals, or up to four groups of dipulse signals, or a
mixture of the two.

Front 12

Describe the main purpose of the digital data group modem.

Back 12

Primarily, it changes cable-side conditioned diphase or dipulse signals to balanced NRZ signals, and vice
versa.

Front 13

Describe the purpose of the low-speed cable driver modem.

Back 13

Changes the cable-side conditioned diphase signal to NRZ for use by the AN/TRC–170 and supplies power
to cable low-speed pulse restorers if required.

Front 14

What data rates are used by the low-speed cable driver modem?

Back 14

It accepts data at 72 to 2,048 Kbps on the equipment side; 2,304 Kbps on the cable side.

Front 15

What is the range of the low-speed cable driver modem with and without pulse restorers?

Back 15

Up to 40 miles with pulse restorers and 1 mile without pulse restorers.

Front 16

Describe the capabilities of the trunk group multiplexer.

Back 16

It multiplexes up to four groups of the 512 Kbps data rate families or four groups of 576 Kbps data rate
families into one supergroup. It will not process group data rates from both families simultaneously. It
demultiplexes a supergroup into separate groups at their original data rates. It can control a KG–81 trunk
encryption device on both the group and supergroup side.

Front 17

Describe the purpose of the KG–81 trunk encryption device.

Back 17

Full-duplex encryption and/or decryption of group or supergroup mission traffic.

Front 18

Describe the purpose of the KG–84 dedicated loop encryption device and the KG–84A general
purpose encryption equipment.

Back 18

Encrypts and/or decrypts telemetry data, processed through the alarm monitor.

Front 19

Describe the purpose of the KY–58 VINSON.

Back 19

Encrypts and/or decrypts digital voice orderwire traffic originating and terminating at the voice orderwire
control unit

Front 20

What is the purpose of the baseband patch panel?

Back 20

Connects the digital group multiplex equipment with the tropospheric scatter modem.

Front 21

Describe the three divided fields of the baseband patch panel.

Back 21

1) The upper jack field provides timing and data connections for the trunk group multiplexer,
tropospheric scatter modem, and trunk encryption device 1. The right side provides patching for black
station clock. Also provided are convenience patch groups A, B, and C, that are internally hard-wired
to jacks in the center jack field.
(2) The center jack field provides connections to the equipment side of the loop group multiplexers,
group modem groups, and the low-speed cable driver modem. The black side of the trunk encryption
device 2 is also available. The dejitterizer input and/or output jacks provide for patching a group
timingsignal directly into the tropospheric scatter modem. Inputs to trunk group multiplexer groups 3
and 4are available. Convenience patch groups A, B, and C pass data and timing signals to the upper
jackfield.
(3) The lower jack field provides data orderwire connections for through patching or patching to and/or
from the dedicated loop encryption device patch panel by way of the level converter jacks. Also
provided are connections for the digital voice orderwire and resync commands to the group and super
group trunk encryption devices.

Front 22

Describe the purpose of the dedicated loop encryption device patch panel.

Back 22

Provides for patching the local telemetry signals to the radio and/or cable side of the AN/TRC–170 and for
monitoring baseband and dedicated loop encryption device patch panel activity

Front 23

Describe the data rates of the tropospheric scatter modem.

Back 23

128 through 4,096 Kbps in the 512 data rate family and 72 through 4,608 Kbps in the 576 Kbps data rate
family.

Front 24

List the types of inputs to the tropospheric scatter modem.

Back 24

Mission data, digital voice orderwire, and up to four data orderwires.

Front 25

What is the purpose of the loop back circuit in the IF patch panel?

Back 25

Provides a calibrated means of applying the tropospheric scatter modem modulator IF output to
tropospheric scatter modem demodulator inputs.

Front 26

Why are the IF patch panels between the AN/TRC–170 V2 and V3 terminals not
interchangeable?

Back 26

The IF test panels are configured differently for each terminal.

Front 27

Describe the outputs of the electrical frequency synthesizer.

Back 27

Stable outputs in the 4.47 to 5.07 GHz range.

Front 28

List the major subassemblies of the RF HPA and state their purpose.

Back 28

(1) The microwave subassembly consists of a klystron amplifier, tuning, and built-in test equipment
circuitry. The klystron is a continuous-wave, HPA that is air-cooled and mechanically tunable. It is
bypassed, and the high voltage power supply is not used when operating in the LOS mode.
(2) The high voltage power supply provides beam and filament voltages for the klystron.
(3) The diplexer enables the transmitter and a receiver to operate from a common antenna port. The
diplexers are used in the V2 model only.

Front 29

Describe the purpose of the downconverters.

Back 29

They preselect, amplify, and postselect the received microwave signal. The LNA and mixer combine the
4.4 to 5.0 GHz receive signal with a 4.47 to 5.07 GHz signal from the synthesizer to produce the 70 MHz
IF.

Front 30

How does the alarm monitor determine overall system performance?

Back 30

Equipment status information and performance data from all major components are reported to the alarm
monitor by the built-in test equipment circuits in each major subassembly. The data is sampled, processed,
and evaluated. From this, overall system performance is determined.

Front 31

List the orderwires and orderwire control units and describe each.

Back 31

(1) The data orderwire consists of a 20-character telemetry status message that can be combined with a
12-telemetry status message from other stations to form a 2 Kbps composite bit stream that is
transmitted to the communication nodal control element.
(2) The voice orderwire control unit connects a VINSON secure voice instrument with the 16 Kbps
digital voice orderwire. This is a first-come, first-served party line system. The unit’s electronic
bridge provides a through connection between the group modems and low-speed cable driver modem
or tropospheric scatter modem.
(3) The remote orderwire control unit accesses the digital voice orderwire through the voice orderwire
control unit. It does not provide secure voice transmission to the voice orderwire control unit.
(4) The analog voice orderwire (the maintenance orderwire) provides unencrypted, full-duplex voice
connection with analog voice orderwire channels of the group modem and low-speed cable driver
modem. It does not connect to the radio side of the AN/TRC–170 terminal.

Front 32

What else does the power entry panel provide power to besides the equipment in the van?

Back 32

The environmental control unit, an external convenience outlet, antenna feedhorn deicers, as well to as an
external main breaker that controls the entire panel.

Front 33

Describe how a surge protection circuit is used and whether it is required for an AN/TRC–170
terminal.

Back 33

It is placed across each phase and the neutral line. It is not required for the van to operate, but without it
there is no prime power surge protection.

Front 34

List the functions of the power distribution unit.

Back 34

It provides a central location to control equipment using primary power for fast power-up and power-down.
It also powers the utility and convenience outlets and ceiling lighting. The front panel meters indicate
current, voltage, and frequency.

Front 35

Describe the purpose of the AC-AC converters.

Back 35

They change the incoming AC signal to a 255 Vpp, 400 Hz quasi-square wave in order to operate the
cooling fans in the shelter. AC-AC converter 1 runs all the blowers in the van, except those in RF HPA#2,
these are run by AC-AC converter 2.

Front 36

List the components and describe the function of the lightning protection assembly.

Back 36

It consists of two, four-section telescoping masts approximately 30 feet tall (assembled), a sky wire 135 feet
long, six anchors, two ground rods, and two mast base plates. The masts are installed 65 feet apart and
slightly behind the two antennas. The sky wire is suspended between the two masts and is grounded on both
ends. The lightning protection assembly acts as a large lightning rod by being the highest point at your
station.

Front 37

Describe the RF output power and frequency band of the TSSR.

Back 37

14.4 to 15.25 GHz with RF output power of about 300 mW.

Front 38

What are the two TSSR antenna lengths, and what are their maximum ranges?

Back 38

1 foot and 2 feet; 10 and 25 miles respectively.

Front 39

List the TSSR conditioned diphase waveform voltage and data rate.

Back 39

3 Vpp conditioned diphase waveform ranging from 72 to 4,608 Kbps.

Front 40

What is the maximum distance the TSSR’s RF and baseband assembly can be physically
separated from each other, using the supplied cable?

Back 40

150 feet.

Front 41

What is the gain of the TSSR’s 1-foot antenna?

Back 41

31 dB.

Front 42

What is the gain of the TSSR’s 2-foot antenna?

Back 42

37 dB.

Front 43

What is the purpose of the input attenuator in the TSSR’s transmit baseband assembly?

Back 43

Compensates for input signal amplitude variations caused by external equipment or varying cable lengths.

Front 44

What is the transmitter deviation in the TSSR’s transmit baseband assembly?

Back 44

±4 MHz.

Front 45

What is the frequency of the transmitter subcarrier (orderwire) in the TSSR’s transmit baseband
assembly?

Back 45

8.5 MHz.

Front 46

Describe the function of the TSSR’s diplexer.

Back 46

It allows the use of a single piece of coaxial cable to pass the transmitter baseband signal from the baseband
assembly to the RF assembly. Also transmitted on the same cable is the receiver 70 MHz IF signal from the
RF assembly to the baseband assembly.

Front 47

In the TSSR’s RF assembly, what is the frequency of the voltage-controlled oscillator, and how is
its accuracy maintained?

Back 47

7 GHz; by a phase-locked loop.

Front 48

What is the purpose of the circulator in the TSSR’s RF assembly?

Back 48

Permits the transmitter and receiver to be connected to the same antenna.

Front 49

In the TSSR’s RF assembly, at what frequency is the tunable filter set?

Back 49

Receive frequency.

Front 50

How is noise generated by the transmitter prevented from interfering with the receiver, in the
TSSR’s RF assembly?

Back 50

The combination of tunable filter and three-port circulator is used to form a notch filter. The notch filter is
tuned to the receiver’s frequency to reduce any noise generated by the transmitter that could interfere with
the receiver.

Front 51

Describe the frequency conversion process in the TSSR’s receive section.

Back 51

The 14.4 to 15.25 GHz RF is mixed with the local oscillator frequency to produce a 70 MHz IF. The local
oscillator frequency is always on the low side of the signal; that is, the local oscillator frequency equals the
signal frequency minus 70 MHz.

Front 52

What is the bandpass frequency range of the 70 MHz IF in the TSSR’s control and distribution
unit?

Back 52

20 MHz.

Front 53

Which unit compensates for changes in the interconnecting cable length in the TSSR’s receive
baseband assembly?

Back 53

Automatic gain control amplifier.

Front 54

In the TSSR’s receive baseband assembly, what type of waveform and data rate is used when
operating in the fiber optic mode?

Back 54

NRZ digital signals at a 6.144 Mbps rate.

Front 55

What type of orderwire capability does the TSSR provide?

Back 55

Full-duplex voice communication.