Antennas 1/2 (C6 Past board: Excel)

ECE Board Exam April 2000

In the study of antenna for radio communications, what very good reason can you conclude why hertz antenna is not recommended in frequencies higher than 2.5 MHz?

Physical dimension is too large

ECE Board Exam November 2000

Which of the following terms id referred to a numerical ratio which relates performance of one antenna to that of another real or theoretical antenna?

Antenna gain

ECE Board Exam April 2000

Which of the following antenna feedline can easily be buried underground for a distance without adverse effects?

Coaxial cable

ECE Board Exam November 1999

In high frequency radio transmission, the lower the radio frequency the ________ of the antenna.

Longer the length

ECE Board Exam April 1999

Determine from the following an advantage of using a trap antenna

Can be used for multiband operation

ECE Board Exam November 1998

Type of antenna which is normally used for satellite tracking services.

Helical

ECE Board Exam April 1998

An increase in the effective power radiated by an antenna in a certain desired direction at the expenses of power radiated in other directions.

Antenna gain

ECE Board Exam April 1998

Two wires that are bent 90 degrees apart

Dipole

ECE Board Exam April 1997

The polarization of a discone antenna is __________

Vertical

ECE Board Exam November 1996

A dipole antenna requires to be fed with 20 kW of power to produce a given signal strength to a particular distant point. If the addition of a reflector makes the same field strength available with an input power of 11 kW. What is the gain in dB obtained by the use of the reflector? (Gain referred to this particular dipole).

ECE Board Exam March 1996

An antenna that is circularly polarized is the

Helical

ECE Board Exam April 2001

In a half-wave antenna, where are are the current nodes?

At the ends

ECE Board Exam November 2000

Electric circuit designed specially to radiate the energy applied to it in the form of electromagnetic waves, normally used to transmit and receive radio waves.

Antenna

ECE Board Exam April 2000

What is the reason why 5/8 whip vertical antenna is of advantage that quarter wave vertical whip antenna?

More gain

ECE Board Exam November 1999

Which of the following antenna where its beamwidth is determined by the dimensions of its horn, lens or reflector?

Aperture antenna

ECE Board Exam 1999

What is the purpose of loading coil in an antenna system?

To produce a resonant system a specific frequency

ECE Board Exam November 1998

What is meant by the term radiation resistance of an antenna?

 An equivalent resistance that would dissipate the same amount of power as that radiated from an antenna

ECE Board Exam April 1998

Where does the maximum current and minimum voltage values on a resonant Hertz dipole exist?

Center of the antenna

ECE Board Exam November 1997

Radiation pattern of a discone.

Omnidirectional

ECE Board Exam April 1997

Which is properly terminated antenna?

Rhombic

ECE Board Exam November 1996

Top loading is used in an antenna in order to increase its _________.

Effective height

ECE Board Exam March 1996

EIRP stands for ________________

Effective isotropic radiated power

ECE Board Exam April 2001

This is the frequency range at which the antenna is expected to perform well as compared to other ranges.

Antenna bandwidth

ECE Board Exam November 2000

The horizontal radiation pattern of an antenna can be described similar to ____________

Number of eight

ECE Board Exam April 2000

What do you call the dissipated power affecting the antenna efficiency caused by arcing effect in high powered transmitters?

Corona discharge

ECE Board Exam November 1999

What measure will you adopt on the antenna system of a VHF or UHF mobile transceivers that has very low height antenna?

Provide loading coil

ECE Board Exam April 1999

What is the reason why Hertz antenna is not normally used to a radio station or receiver or transmitter antenna that has frequency above 2 MHz?

The antenna will be physically very large

ECE Board Exam April 1999

What is the folded dipole antenna?

A dipole whose ends are connected by another one-half wavelength piece of wire

ECE Board Exam April 1998

What is meant by the term antenna efficiency?

Efficiency = radiation resistance / total resistance x 100%

ECE Board Exam November 1998

Determine the effective radiated power of 20 kW TV broadcast transmitter whose antenna has a field gain of 2.

ECE Board Exam November 1997

Unity gain antenna.

Isotropic

ECE Board Exam April 2001

In order to fully utilize the ________, a quarter-wave vertical antenna should require an excellent ground system.

Mirror image principle

ECE Board Exam November 2000

One of the following is a type of radio antenna used in transmission and reception of microwave signals.

Horn antenna

ECE Board Exam April 2000

An inductor that is inserted in an antenna element or transmission line for the purpose of producing a resonant system at specific frequency.

Loading coil

ECE Board Exam November 1999

In order to have an effective radio antenna, the design of its radiator must have a minimum length equivalent to ___________.

Wavelength/4

ECE Board Exam The antenna property of interchangeability for transmitting and receiving electromagnetic energy under the same radio frequency is referred to as ___________.

Reciprocity

ECE Board Exam November 1998

What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?

Antenna efficiency

ECE Board Exam April 1997

__________ is a device that detects both vertically and horizontally polarized signal simultaneously.

Orthomode transducer

ECE Board Exam November 1996

Which is the non-resonant antenna?

Rhombic antenna

-------------------- resonant antenna-------------------

Broadside antenna

Folded dipole

End fire array

ECE Board Exam March 1996

An antenna which is not resonant at a particular frequency and so can be used over a wide band of frequencies is called

Aperiodic

ECE Board Exam April 2001

What is the usual electrical length of a driven element in a HF beam antenna?

1/2 wavelength

ECE Board Exam November 2000

What is an antenna element that is not directly connected to the feed line, but which affects the radiation pattern and feed-point impedance of the antenna?

Parasitic element

ECE Board Exam April 2000

What is the purpose of the two yagi beam antenna on a VHF TV receiver?

For receiving low and high band stations

ECE Board Exam November 1999

What is a parasitic element of an antenna?

An element that receives its excitation from mutual coupling rather than from a transmission line

ECE Board Exam April 1999

One of the following refers to the usage of a small loop antenna in radio communications

For direction finding purposes

ECE Board Exam April 1998

How can the antenna efficiency of an HF grounded vertical antenna be made comparable to that of a half-wave antenna?

By installing a good ground radial system

ECE Board Exam November 1998

Determine the dB gain of a receing antenna which delivers a microvolt signal to a transmission line over that of an antenna that delivers a 2 microvolt signal under identical circumstances.

ECE Board Exam November 1997

A region in front of a paraboloid antenna

Transmission zone

Fraunhofer

Fresnel

ECE Board Exam April 1997

How much does the radiated power of an antenna increases if its current increased by 3.3 times?

ECE Board Exam November 1996

A horizontal antenna is

Horizontally polarized

ECE Board Exam March 1996

The capture area of an antenna is directly proportional to the

Gain of the antenna

ECE Board Exam April 2001

What property of an antenna which is a reason for its efficiency in receiving and transmitting the intended electromagnetic energy and is physically identical to its physical configuration?

Polarization

ECE Board Exam April 1998

Known as the technique for adding a series inductor at or near the center of an antenna element in order to cancel the capacitive reactance of an antenna.

Loading coil

ECE Board Exam November 1997

A helical antenna is used for satellite tracking because of ___________

Circular polarization

ECE Board Exam April 1997

What is the estimated medium wind loading in the Philippines for antenna tower design?

200 kph

ECE Board Exam March 1996

The standard reference antenna for the directive gain is __________

Isotropic antenna

ECE Board Exam April 2001

One of the following is referred to as a way of increasing the electrical length of an antenna.

By adding an inductor in series

ECE Board Exam November 2000

A type of antenna that has physical length equivalent to one half-wavelength of the radio frequency being used

Hertz

ECE Board Exam April 2000

Ratio of radiation resistance to the total resistance on an antenna system.

Antenna efficiency

ECE Board Exam November 1999

Due to the presence of parallel LC networks in the trap antenna, one of the following is a disadvantage of using this kind of antenna.

Radiate harmonics

ECE Board Exam April 1999

How can the approximate beamwidth of a rotatable beam antenna be determined?

Note the two points where the signal strength of the antenna is down 3 dB from the maximum signal point and compute the angular difference.

ECE Board Exam April 1998

What is meant by the term antenna bandwidth?

The frequency range over which the antenna can be expected to perform well

ECE Board Exam November 1997

What makes an antenna physically long but electrically short?

Adding C in series

ECE Board Exam March 1996

A type of an undergrounded antenna is a/an _____ antenna

Hertz

ECE Board Exam April 2001

What is the term for an antenna element which is supplied power from a transmitter through a transmission line?

Driven element

ECE Board Exam November 2000

In the propagation of radio signals through an aerial, at what angle does magnetic field are positioned with reference to the direction of the propagation

90

ECE Board Exam April 2000

What happens to the resonant frequency of a vertical antenna when it is made to lengthen?

Decreases

ECE Board Exam November 1999

How do you compare the length of the reflector element of a parasitic beam antenna with that of its driven element?

Reflector element is 5% longer

ECE Board Exam April 1999

What do you call the LC networks inserted in an antenna element to provide multiband operation?

Traps

ECE Board Exam April 1998

Where does the voltage node of a half-wave antenna exist?

At feed point

ECE Board Exam November 1997

Radiation characteristics of a dipole.

Bidirectional

ECE Board Exam April 1997

The minimum number of turns a helix antenna must have.

3

ECE Board Exam March 1996/November 1999

What is meant by antenna gain?

The numeric ratio relating the radiated signal strength of an antenna to that of another antenna.

ECE Board Exam 2001

Which of the following type of radio communication antenna does not deliver an omni-directional radiation pattern?

Yagi

ECE Board Exam November 2000

In radio communication, the term trap antenna is referred to, in one of the following statements:

Antenna which can be used on more than one band due to the use of parallel LC networks.

ECE Board Exam April 2000

Which of the following is the normal electrical length of a driven element of an HF beam antenna?

1/2  wavelength

ECE Board Exam November 1999

What is the purpose of a certain antenna component composed of a parallel LC networks inserted in the antenna called traps?

Provide a multiband operation

ECE Board Exam April 1999

In radio communications technology, the basic functions of an antenna is to __________

Generate and collect electromagnetic energy

ECE Board Exam April 19983

This is a flexible vertical rod antenna commonly used on mobiles.

Whip

ECE Board Exam November 1997

Determine the gain of a 6 ft. parabolic dish operating at 1800 MHz.

ECE Board Exam April 1997

When testing transmitter to prevent interfering with other stations, which type of antenna must be used?

Dummy antenna

ECE Board Exam March 1996

It consists of a number of dipoles of equal size, equally spaced along a straight line with all dipoles fed in the same phase from the source.

Broadside array

ECE Board Exam November 2000

Radio wave concentration in the direction of the signal emitted by a directional antenna

Major lobe radiation

ECE Board Exam April 2000

Determine the approximate length of a simple whip quarter wave antenna at UHF frequency of 450.25 MHz.

ECE Board Exam November 1999

Refers to the numerical ratio relating to the radiated signal strength of an antenna to that of another antenna.

Antenna gain

ECE Board Exam April 1998

What is dummy antenna?

A non-radiating load for a transmitter used for testing

ECE Board Exam November 1997

A convenient method of determining antenna impedance.

Smith chart

ECE Board Exam April 1997

A device that radiates electromagnetic energy and or intercepts electromagnetic radiation.

Antenna

ECE Board Exam March 1996

A type of array antenna which consists of one half-wave driven dipole, one reflector and one director.

Yagi-Uda

ECE Board Exam November 2000

Referred as an effect of parasitic elements in an antenna system

Increase its directivity

ECE Board Exam November 1999

Which of the following is taken as the standard reference antenna for directive gain?

Isotropic

ECE Board Exam April 2000

What is the length of a simple quarter wave antenna using a VHF frequency of 150.55 MHz?