Unit 2. Very High Frequency Omni-directional and Radio Range Tactical Air Navigation System

Question 1

Match each VOR unit in column B with their function(s) in column A. Some column B items may be used more than once.

___ 1. Is a DC-to-DC converter.
___ 2. Produces the basic RF signals.
___ 3. Contains a DC-to-AC inverter.
___ 4. Generates the station identification.
___ 5. Provide test signals to align monitors.
___ 6. Collects fault isolation measurements.
___ 7. Is a AC-to-DC converter.
___ 8. Responsible for system fault detection.
___ 9. Provides radio transmitter high-power modulation voltage. ___10. Monitors automatic-ground check system.

Answer 1

1. (1) d. (2) c. (3) f. (4) c. (5) a. (6) b. (7) e. (8) b. (9) d. (10) b.

Question 2

Match each TACAN unit in column B to their function(s) in column A. Some column B items may be used more than once or not at all.

Column A
___ 1. Provides AC power for the fans.
___ 2. Receives and decodes aircraft interrogations. ___ 3. Provides regulated 65 VDC.
___ 4. Raises output level to 3kW peak at the antenna. ___ 5. Generates test interrogation signals.
___ 6. Directs aircraft interrogations to the receiver. ___ 7. Measures critical system parameters.
___ 8. Generates random squitter pulses.
Column B
a. Radio frequency amplifier 2A1.
b. Transponder 2A2.
c. Radio frequency monitors 2A3/2A4. d. Power supply 2A6.

Answer 2

(1) d. (2) b. (3) d. (4) a. (5) c. (6) a. (7) c. (8) b.

Question 3

3. Which VORTAC system is provided with battery backup power?

Answer 3

The VOR monitors must be wired into the local PC and the VOR key input is wired into the TACAN transponder.

Question 4

4. What changes are required when the VOR and TACAN systems are placed in the VORTAC configuration?

Answer 4

VOR system.

Question 5

208. Operating the local and remote PC

1. What operations can you perform utilizing either the local or remote PCs?

Answer 5

Collect, display, and print measured parameter data, turn on/off the transmitter ID, and alarm bypass.

Question 6

2. What are the two main windows into which the PC displays are divided?

Answer 6

System status window and the master menu window.

Question 7

3. How would you activate a submenu on the local and remote PC?

Answer 7

Clicking specific buttons on the menus.

Question 8

4. Explain the data from the monitors being displayed on the PC.

Answer 8

Data from both monitors is displayed along with the upper and lower limits of each parameter.

Question 9

209. Control indicator

1. What is the purpose of the control indicator?

Answer 9

To provide remote start and stop control and status indications for VOR and TACAN installations.

Question 10

2. What three functions does the control indicator perform?

Answer 10

(1) Converts control panel inputs into signals that can be transmitted to the VOR and TACAN sites.
(2) Monitors return signals from these sites.
(3) Provides both control signals and operating power to status indicators and audible alarm.

Question 11

3. What adjustments are ATC personnel allowed to perform on the control indicator?

Answer 11

Audio volume control and indicator brightness.

Question 12

4. What are the four basic areas of the CODEC circuitry?

Answer 12

(1) The VOR transmit/receive circuits.
(2) The TACAN transmit/receive circuits.
(3) The display/alarm sense circuits.
(4) The oscillator (alarm)/audio amplifier circuits.

Question 13

5. Which frequency is produced by placing the start/stop switch in the start position? In the stop position?

Answer 13

Start=74Hz.Stop=66Hz.

Question 14

6. What do the binary signals produced by the VOR and TACAN receive circuits on the CODEC card reflect?

Answer 14

The actual ON or OFF status of the remote transmitters.

Question 15

7. What is the purpose of BT1 and BT2 in the control-indicator power supply?

Answer 15

To assume the operating load of the control indicator in a power failure or rectifier/filter shutdown.

Question 16

210. Capabilities and limitations

1. How long can the VOR facility operate at full power on backup batteries?

Answer 16

A minimum of two hours.

Question 17

2. What’s the frequency range of the radio transmitter?

Answer 17

108 to 118 MHz, 0.001%.

Question 18

3. Describe the monitor’s fail-safe operation.

Answer 18

Any internal monitor malfunction will cause an alarm, but will not cause system shutdown.

Question 19

4. What are the identification alarm limits?

Answer 19

An alarm will occur within six seconds for continuous ID or 30 seconds for absent ID.

Question 20

211. Block diagram theory of operation

1. What two signals does the integral goniometer produce?

Answer 20

Sideband 1 and sideband 2.

Question 21

2. From what device does the VOR transmitter receive on/off control signals?

Answer 21

The control indicator located in the ATC facility.

Question 22

3. What ground check error parameters do the monitors check?

Answer 22

Octantal, quadrantal, and duantal.

Question 23

4. Why does the VOR test generator provide outputs?

Answer 23

For monitor calibration, integrity checks, and fault isolation.

Question 24

5. What three DC voltages does power supply two provide?

Answer 24

+18V , –18V , and +9V .

Question 25

212. Capabilities and limitations

1. What’s the purpose of the TACAN?

Answer 25

To provide bearing and distance information for up to 100 aircraft at a distance of up to 200 nautical miles.

Question 26

2. What’s the TACAN’s frequency range?

Answer 26

962 to 1,213 MHz.

Question 27

3. List the TACAN parameters that are continuously monitored.

Answer 27

Reply delay, pulse spacing, efficiency, output pulse rate, identification, mod gen status, north reference burst, auxiliary reference burst, and antenna scan rate.

Question 28

4. Which transponder outputs have the highest priority of transmission?

Answer 28

North and auxiliary reference burst pulse pairs.

Question 29

5. Describe the X mode north reference azimuth group.

Answer 29

12 pulse pairs (12 s between pulses of a pair) spaced 30 s apart.

Question 30

6. What four outputs does the power supply provide?

Answer 30

+65 VDC, +17.5 VDC, 17.5 VDC, and +10 VDC.

Question 31

213. Block diagram theory of operation

1. What does the RFA do with the 400W RF DRIVE?

Answer 31

Amplifies the drive signal to 3kW peak.

Question 32

2. With what triggers are azimuth reference group pulses present in the 400W RF DRIVE synchronized?

Answer 32

NORTH TRIGGER and AUX TRIGGER.

Question 33

3. Which component generates the station Morse code identity?

Answer 33

The primary monitor, normally monitor A.

Question 34

4. What component controls the overall reply delay?

Answer 34

The monitor.

Question 35

5. What determines the controlling monitor?

Answer 35

The state of the monitor A CPU MAL signal.

Question 36

6. What information do the SOLID STATE ANTENNA STATUS lines provide?

Answer 36

They tell the monitor that a solid state antenna is present, and indicate if a soft fail, hard fail, or clock fail condition exists.

Question 37

214. TACAN signal characteristics

1. What is the pulse pair spacing for X mode?

Answer 37

12μs.

Question 38

2. Which parts make up the pulsed output of the TACAN? How many pulses per second comprise each?

Answer 38

(1) North reference burst; 360 pulse/second.
(2) Auxiliary reference burst; 1440 pulse/second.
(3) Identification; 5400 pulse/second.
(4) DME interrogation; random.
(5) Squitter; (2700 - DME) X 2, 5400 maximum.

Question 39

3. What is the first likely result of a severe decrease in beacon duty cycle?

Answer 39

Holes in the output pattern and 135 Hz instability in the aircraft receiver.

Question 40

4. How does any interrogating aircraft recognize its reply from the replies to the other aircraft in the area?

Answer 40

The aircraft will be able to recognize their own replies by the pulse spacing between pair groups.

Question 41

5. What is the principal method used to minimize co-channel interference?

Answer 41

TACAN stations within 400 miles of each other are not assigned adjacent frequencies.

Question 42

6. List the functions of the antenna group.

Answer 42

Power divider, azimuth feeds, vertical columns, and the multiplexer.

Question 43

7. What is the modulation generator?

Answer 43

Makes NRB and ARB triggers, which are used to produce NRBs and ARBs in the transponder, the 15 and 135 Hz modulation, and causes the radiation pattern to appear to rotate.

Question 44

8. What is the only card in the antenna/modulation generator that requires alignment?

Answer 44

Modulation generator microprocessor card.