# Analog Communications Questions and Answers – Reactance Modulator

This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Reactance Modulator”.

1. Which is the dominant mode for a rectangular waveguide?
a) TE 01
b) TM 01
c) TE 10
d) TM 10

Explanation: Rectangular waveguides are the earliest form of transmission lines. It supports TM and TE mode, which stands for Transverse Magnetic waves and Transverse Electric waves respectively, but it does not support TEM, Transverse Electromagnetic waves, mode. A rectangular waveguide can’t propagate below some certain frequency. The dominant mode for it is TE 10 mode.

2. EIRP stands for _________
b) Effective Isotropic Reflected Power
c) Effective Isotropic Refracted Power
d) Effective Isotropic Regulated Power

Explanation: ERIP stands for Effective Isotropic Radiated Power. It is basically the output power when a signal is concentrated into a smaller area with the help of the antenna.

3. Characteristic impedance of a cable depends only on the resistance per foot of the wire used.
a) True
b) False

Explanation: Characteristic Impedance is the ratio of voltage amplitude to current amplitude of a propagating electromagnetic wave. The characteristic impedance of a cable depends on the inductance per foot and the capacitance per foot.

4. When calculating the maximum number of users, limiting factor in FDM is ___________
a) bandwidth of each signal
b) type of each signal
c) amplitude of each signal
d) length of the channel

Explanation: When calculating the maximum users in frequency division multiplexing, the bandwidth of each transmitting signal must be observed very carefully and thus it is also the limiting factor in FDM.

5. CDMA stands for Carrier Division Multiple Access.
a) True
b) False

Explanation: CDMA stands for Code Division Multiple Access. It refers to any protocol that is used in second generation and third generation wireless communication.
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6. QPSK symbol contains ________
a) a byte
b) 4 bits
c) a dibit
d) 8 bits

Explanation: QPSK stands for Quadrature Phase Shift Keying which is a digital signal modulation scheme. In QPSK, only two bits are transmitted per symbol. It represents 00, 01, 10, 11

7. What is the full form of ATM?
a) Asynchronous Transfer Mode
b) Asynchronous Transmission Mode
c) Automatic Transmission Mode
d) Automatic Transfer Mode

Explanation: ATM stands for Asynchronous Transfer Mode. It uses asynchronous time division multiplexing and encodes data into small but fixes size packets.

8. Who invented the Ethernet?
a) IBM
b) Xerox
c) Intel
d) Cisco

Explanation: Ethernet is a computer technology mostly used in LANs. LAN connects devices sharing a common network or linked by the same server. Ethernet was invented by Xerox.

9. MAN stands for ________
a) Metropolitan Access Network
b) Metropolitan Area Network
c) Multiple Area Network
d) Multiple Access Network

Explanation: MAN stands for Metropolitan Area Network. It interconnects computers that are under a fixed geographic area larger than that covered by LAN but smaller than the area covered by WAN.

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