ELECTRONICS SYSTEMS AND TECHNOLOGIES
1. Water vapor causes significant attenuation of electromagnetic waves at higher frequencies. The first
absorption band due to peaks at approximately ________.
A. 22 GHz * C. 119 GHz
B. 60 GHz D. 6 Ghz
2. A 150-pound conical-shaped satellite and was the first artificial satellite used for relaying terrestrial
communications.
A. Courier C. Echo
B. Molniya D. Score *
3. __________ is the process of converting an infinite number of possibilities to a finite number of
conditions.
A. Sampling C. Quantization *
B. Conversion D. Encoding
4. A coaxial cable that is made to radiate by using a shield that does not cover the cable completely.
Typically there are slots in a spiral shield. It is useful when radio communication is required in areas such
as tunnels and underground malls.
A. Leaky Feeders * C. Slotted Coaxial Line
B. Rake-Type Coaxial Cable D. all of the above
5. A small length of wire, connected at only one end and used as a capacitance to ground.
A. Gimmick * C. Capacitive Hat
B. Loading Coil D. Coaxial Cable
6. An antenna that is characterized by very wide bandwidth, covering approximately a 10:1 frequency
range, and an omnidirectional pattern in the horizontal plane.
A. Log Periodic C. Broadside Array
B. Discone * D. Horn Antenna
7. A varactor-tuned oscillator uses an inductance of 25 microH with a varactor having a maximum
capacitance of 45 pF in the frequency-determining circuit. Calculate the range of frequencies for this
oscillator, with a tuning voltage that varies from 1V to 10V.
A. 7.67 to 9.90 MHz C. 6.24 to 10.20 MHz*
B. 1.43 to 2.15 MHz D. 5.34 to 6.72 MHz
8. A quartz watch is guaranteed accurate to 15 seconds per month. Assuming a month has 30 days,
calculate the accuracy of the crystal oscillator in the watch in parts per million.
A. 6.7 ppm C. 1.5 ppm
B. 3.6 ppm D. 5.8 ppm*
9. An AM transmitter uses high-level modulation. The power amplifier runs from a 12V source, putting out
a carrier power of 75 W, at an efficiency of 75%. What is the dc current drawn by this stage from the
power supply?
A. 100A C. 8.33A*
B. 7.88 A D. 125 A
10. The range of frequencies over which a PLL will cause the input of the VCO signals to remain
synchronized is known as the ________ range.
A. capture C. acquisition
B. lock* D. any of these
11. If the length of a short-circuited stub is less than quarter-wavelength but greater than 0, the stub
behaves as
A. inductor* C. resistor
B. capacitor D. complex
12. The coding rate for video cd with stereo channels using PCM 16 bits per sample at frequency of 20 KHz
before error correction is
A. 1.28 Mbps C. 1.41 Mbps*
B. 12.8 Mbps D. 14.1 Mbps
13. A telephone line has a bandwidth of 3.2 kHz and signal-to-noise ratio of 34 dB. A signal is transmitted
down this line using a four-level code. What is the maximum data rate neglecting Hartley’s theorem?
A. 72.6 kbps C. 36.3 kbps *
B. 12.8 kbps D. 25.6 kbps
14. The radio wavelength known as _____ falls within the ultra high frequency range.
A. centimetric C. decimetric*
B. decametric D. myriametric
15. The output phase of a binary input Logic 0 of BPSK is
A. Sin ωct C. Cos ωct
B. –Sin ωct * D. -Cos ωct
16. A reactance modulator looks like a capacitance of 35 pF in parallel with the oscillator-tuned circuit
whose inductance is 50 µH and capacitance is 40 pF. What is the center frequency of the oscillator prior
to FM?
A. 1.43 MHz C. 3.56 MHz
B. 2.6 MHz * D. 3.8 MHz
17. An FM signal has a frequency deviation of 5KHz and modulating frequency of 3 KHz. The signal-to-noise
at the input to the receiver detector is 20dB. Calculate the approximate signal-to-noise ratio in dB at the
output.
A. 50 C. 100
B. 33.9 D. 24.4*
18. How many repeaters could be eliminated from a system spanning 2000km if the repeater spacing could
be increased to 45km from 40kms?
A. 5* C. 8
B. 6 D. 4
19. Find the noise temperature of an antenna on a satellite if it looks at the earth (giving it a sky noise
temperature of 290 K) and is coupled to the reference plane by a waveguide with loss of 0.3 dB.
A. 290 °C C. 17 °C*
B. 563 °K D. 280 °K
20. What is the duty cycle of a radar pulse if the pulse width is 1 us, the pulse repetition rate is 900, and the
average power is 18 W?
A. 0.09% * C. 0.90%
B. 0.99% D. 1.00%
21. The biggest disadvantage of PCM is
A. its inability to handle analog signals
B. the high error rate which its quantizing noise introduces
C. its incompatibility with TDM
D. the large bandwidths that are required for it *
22. A microwave communications uses plane reflectors as passive repeaters. The diameter of the parabolic
antenna is 18 ft., while the effective area is 310 ft. Determine the reflector coupling factor.
A. 0.76 C. 0.92
B. 0.906 * D. 0.706
23. Medium Earth Orbit (MEO) satellite operates in the _____ frequency band.
A. 2 - 18 GHz C. 1.2 - 1.66 GHz *
B. 1.0 - 2.5 GHz D. 6 - 12 GHz
24. Two adjacent minima on a slotted line are 23 cm apart. Find the frequency, assuming a velocity factor of
95%.
A. 260 MHz C. 206 MHz
B. 620 MHz * D. 602 MHz
25. Suppose an input signal to a u-law compressor has a positive voltage and an amplitude 25% of the
maximum possible. Calculate the output voltage as a percentage of the maximum output.
A. 0.852Vo C. 0.752Vo *
B. 0.812Vo D. 0.215Vo
26. An angle of inclination that will result a rotation of line of apside equal to zero is:
A. 46.3 deg C. 34.6 deg
B. 63.4 deg * D. 43.6 deg
27. The receiving installation whose G/T was found to be 20.6 dB is used as a ground terminal to receive a
signal from a satellite at a distance of 38,000 km. The satellite has a transmitter power of 50 watts and an
antenna gain of 30 dBi. Assume losses between the satellite transmitter and its antenna are negligible.
The frequency is 12 GHz. Calculate the carrier-to-noise at the receiver, for a bandwidth of 1 MHz.
A. 30.6 dB * C. 40.1 dB
B. 38.5 dB D. 35.6 dB
28. A waveguide has a cutoff frequency for the dominant mode of 10GHz. Two signals with frequencies of
12 and 17 GHz propagate down a 50m length of the guide. Calculate the difference in arrival time for the
two.
A. 95.5 ns * C. 76.2 ns
B. 105.6 ns D. 65 ns
29. A radar transmitter has a power of 10kW and operates at a frequency of 9.5 GHz. Its signal reflects from
a target 15 km away with a radar cross section of 10.2 square meter. The gain of the antenna is 20 dBi.
Calculate the received signal power.
A. 10.1 fW * C. 3.41 fW
B. 23.1 fW D. 98 fW
30. A certain antenna has a gain of 7 dB with respect to an isotropic radiator. How much power would it
absorb from a signal with a field strength of 50 uV/m, at a frequency of 200MHz?
A. 33.23 pW C. 111.7 pW
B. 5.95 pW* D. 9.55 pW
