EST - Microwave - A

The microwave path wherein the

microwave beam just barely touches the

obstruction.

a. LOS

b. Direct path

c. Grazing Path

d. Obstructed Path

C

A value of "K" where there is no refractive

effect, and the signal path is a straight

line. Under these conditions "effective

earth bulge" will be equal to "physical (or

true) earth bulge."

a. negative

b. 1

c. 4/3

d. infinity

B

Topographical maps are used for

microwave communications system design

because it gives information about elevations

thru:

a. scales

b. contour lines

c. longitudes

d. latitudes

B

A redirection by diffraction of a portion pf

the incident radiation that strikes a well-

defined obstacle such as a mountain range

or the edge of a building.

a. Huygen's principle

b. retransmission

c. knife-edge diffraction

d. redirection

C

In analog microwave systems, additional

repeaters increase the:

a. reliability

b. noise level

c. jitter

d. all of the above

B

Satisfactory performance of a digital

microwave system requires a:

a. low level of transmitted power

b. high level of ERP

c. good energy per bit per transmitted

watt ratio

d. good energy per bit per noise density

ratio

D

An advantage of digital techniques over

analog in a microwave system is:

a. less bandwidth is required

b. accumulation of noise is reduced

c. it requires less power

d. all of the above

B

A microwave system is composed of three

links, all three must function in order for

the system to work. Each has a reliability

of 90%. The total system reliability is:

a. 72.9%

b. 90%

c. 99%

d. 2.7%

A

Probably the most important parameter

considered when evaluating the performance

of a microwave communications system is

a. system gain

b. carrier-to-noise ratio

c. fade margin

d. signal-to-noise ratio

B

A fade margin of 38dB has a reliability of:

a. 99%

b. 99.9%

c. 99.99%

d. 99.999%

C

A typical microwave system uses a

transmitted power of about:

a. 2 mwatts

b. 2 watts

c. 20 watts

d. 2000 watts

B

What is the required minimum transmit

power to achieve a carrier-to-noise ratio of

24dB with a system gain of 113.35dB

operating over a 10MHz bandwidth?

a. -14.62dB

b. -14.62dBm

c. 33dB

d. 33dBm

D

A parabolic antenna has a diameter of

3 m, an efficiency of 60%, and operates at

a frequency of 4 GHz. Calculate its gain

and beamwidth respectively.

a. 29 dB, 1.75

b. 29 dB, 17.5

c. 39 dB, 1.75

d. 39 dB, 17.5

C

What is the free-space loss in dB

between two microwave parabolic

antennas 38 km apart operating at 7 GHz?

a. 81 dB

b. 121 dB

c. 141 dB

d. 205 dB

C

Calculate the fade margin of a digital microwave link operating at 5 GHz with the following specs:

transceiver power output = 33 dBm

parabolic dish antenna diameter (with n=.55) at each end = 1.675ft

distance = 25 km

Rx threshold = -87 dBm

cable and other losses = 25.3 dB

a. 49.46

b. 12.24

c. 47.74

d. 47.71

B

A link with little or no Fade Margin may

experience periodic outages due to:

a. low availability

b. irregularities in link design

c. path fading phenomena

d. temperature inversion

C

Large fade margin is not necessary for:

a. very long links

b. links with more than 10km distance

c. shorter link

d. higher performance, larger and more

expensive antennas

C

The two most significant types of signal

strength loss are:

a. path length and choice of frequency

b. free space loss and path length

c. rain and multipath attenuation

d. multi-path fading and transmission line

loss

C

Solve for the total height extended in

feet for an obstacle situated 25-mi away

for a 35-mi microwave system operating

at 8 GHz assuming if the tree growth

exists, add 40 ft for the trees and 10 ft forl

additional growth.

a. 185 ft

b. 195 ft

c. 202 ft

d. 216 ft

D

In reference to Fresnel zone radius,

which of the following requires the most

clearance of any point in the path?

a. endpoints

b. midpoint

c. 3/4 of the path distance

d. all must have a maximum clearance

B

As the length of the path increase, the

size of the Fresnel Zone:

a. decreases

b. increases

c. not affected

d. can be any of the above

B

The effect on signal in the even Fresnel

Zone is:

a. reinforcement

b. increased by two folds

c. cancellation

d. none

C

A type of diversity reception, where the

output of the transmitter is fed to two or

more antennas that are physically

separated by an appreciable number of

wavelengths.

a. frequency

b. space

c. angle

d. polarization

B

One of the most economic way to

overbuild the link in order to increase the

RSL above that of the designed RSL to

include the fade margin is to:

a. increase the operating frequency

b. increase the number of active repeaters

c. stiffen the tower

d. increase antenna aperture

D

When using space diversity, the

separation distance should be at least

wavelengths and preferably

wavelengths.

a. 50, 80

b. 60, 90

c. 70, 100

d. 80, 110

C

The general term for any kind of

radiation disturbance on radio-link

systems.

a. noise

b. interference

c. fading

d. attenuation

B

For a microwave link situated in desert

areas, which of the following is most

critical to occur?

a. ground reflection

b. multipath fading

c. ducting

d. both b and c

D

A typical heated radome in high-frequency bands has almost:

a. 0.2 dB loss

b. 2 dB loss

c. 0.5 dB loss

d. 5dB loss

B

Which of the following has an inversely

proportional effect to reliability?

a. antenna size

b. path length

c. redundancy

d. signal processing equipment

B

Microwave links where there is no

diversity or protection are classified as:

a. Unprotected

b. 1 + 1 configuration

c. 1 + 0 configuration

d. more than one of the choices

D

Which of the following statements is correct when it comes to the performance of a digital radio system, in terms of its bit error rate (BER) or probability of bit error (Pe)?

a. BER is solely controlled by the signal strength, and not by the Eb/No at the receiver

b. BER is not solely controlled by the signal strength, but rather by the Eb/No at the receiver

c. BER is not solely controlled by the signal strength and Eb/No at the receiver

d. BER is controlled by the signal strength and Eb/No at the receiver

B