Basic Radio Theory | JAA ATPL Exam Questions.

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Basic Radio Theory | JAA ATPL Exam Questions.

Postby CaptainMFT » 18 Sep 2016 05:17

Decimetric waves correspond to the frequency range:

3000 to 30000 MHz
3000 to 30000 KHz
300 to 3000 MHz
300 to 3000 KHz


Decimeter: A metric unit of length, equal to one tenth of a meter.

Decameter: A metric unit of length, equal to 10 meters.

According to ICAO Annex 10, in which frequency band(s) does a locator normally transmit?


A locator outer marker, or LOM, is a navigation aid used as part of an instrument landing system (ILS) instrument approach. LOM is a non-directional beacon (NDB) co-located with the outer marker beacon in the ILS approach, so that aircraft can navigate directly to the location using the NDB as well as be alerted when they fly over it by the beacon.

A low or medium frequency radio beacon transmits nondirectional signals whereby the pilot of an aircraft properly equipped can determine bearings and "home" on the station. These facilities normally operate in a frequency band of 190 to 535 kilohertz (kHz), according to ICAO Annex 10 the frequency range for NDBs is between 190 and 1750 kHz, and transmit a continuous carrier with either 400 or 1020 hertz (Hz) modulation. All radio beacons except the compass locators transmit a continuous three-letter identification in code except during voice transmissions.

A marker beacon is a particular type of VHF radio beacon used in aviation, usually in conjunction with an instrument landing system (ILS), to give pilots a means to determine position along an established route to a destination such as a runway. Markers operate at 75 MHz (VHF).

An aircraft travelling at 330 meters a second transmits a signal at 10 GHz to a stationary receiver. If the aircraft is flying directly towards the receiver and they are approximately at the same height the received frequency will be:

11 MHz
10,000011 GHz
9,999989 GHz
11 GHz

Doppler Shift (Hz) = Relative velocity (metres per second) / Transmitted wavelength (metres)

Wavelength = Speed of Sound / Frequency

= 3 x 10^8 / 10 GHz or

= 300,000,000 / 10,000,000,000

= 0.03 meters

Dopler Shift = 330/0.03 = 11,000 Hz

Received frequecy = 10 GHz + 11,000 HZ = 10,000011000 Hz or 10.000011 GHz

Which of the following statements is correct in respect of a RF signal:

the plane of polarisation is dictated by the oscillator unit in the transmitter
the electrical component of the signal is parallel to the aerial
the magnetic component of the signal is parallel to the aerial
both the electrical and magnetic components are parallel to the aerial

A half wave dipole aerial suitable for transmitting an RF signal at 18 MHz should have an effective length of:

16,67 metres
166,67 metres
83,33 metres
8,33 metres

RF signal at 18 MHz has a wavelength = Speed of sound / frequency

= 3 x 10^8 / 18 MHz

= 16.66 meters

Half wave dipole = 16.66 / 2 = 8.33 meters

Which of the following statements is true?

A broad bandwidth gives a narrow beam width
A narrow bandwidth improves beam width
A transmission's bandwidth is affected by the design of the aerial
Bandwidth must be reduced in order to reduce noise

Diffraction of a RF signal is a displacement of its propagation path due to:

reflection from the surface
passing over or through mediums of different conductivity
passing over obstacles with dimensions close to the wavelength
passing through ionised regions of the upper atmosphere

One major consideration that determines if radio waves are blocked involves the concept of diffraction. This depends on the wavelength of the radiation and the size of the obstacle in which it is attempting to penetrate. Low frequencies have a easier time passing over large objects such as hills, while higher frequencies work better with small obstacles such as rooftops. This can be very useful in making a radio wave blocked using the knife-edge diffraction method. If a wave does not have a line of sight over an object, a sharp edge can be created, which causes the radio wave to be blocked and redirected to where the broadcast should go.

Refraction of an electro-magnetic radiation is:

The bending of its propagation path as it passes through or over areas of different electrical conductivity
The loss of power as it passes through or over areas of different electrical conductivity
Is bending resultant from reflection from objects
Is loss of power through reflection from objects

With regards to radio waves, which statement is true?

They are reflected by metallic objects with a size compatible to the wavelength
The longer the wavelength the greater the surface attenuation
They travel at 186,000 nm a second in a vacuum
High frequencies need large aerials

You are at an altitude of 9,000 feet. At a range of 200 nm from a VHF communications transmitter, and you are receiving a good signal.

You should expect this since the transmitter is at a height of 2.000 feet
You should have been receiving the signal from a range of 240 nm
You are probably receiving a sky wave signal
You are probably receiving a duct propagation signal

To establish and maintain effective HF communications the frequency used at a given range: "should be decreased at night". 

sun down frequency down

Refer to figure.In the following diagram, the phase difference between the two signals is: 180°


To determine phase difference find where your wave rises through the neutral position and read the phase of the reference wave (solid one in this fig) at that point.

Ground direction finding at aerodromes utilizes what frequencies?

"VHF at civil aerodromes and UHF at military aerodromes". 

The emission characteristics A3E describe:

VHF communications
HF communications

Q codes

QDR - Magnetic Bearing From
QDM - Magnetic Bearing To
QTE - True Bearing From
QUJ - True Bearing To

The gain of an aerial is a measure of its ability to:

Focus power
Transmit intelligence
Overcome transmitter line resistance
Compensate for attenuation

What is the lowest frequency where freedom from static interference can be guaranteed?

3 MHz
30 MHz
300 MHz
3 GHz

Start of VHF

The VHF frequency band has a wavelength limit of:

100 m to 10 m
1 m to 100 cms
10 m to 1 m
100 cms to 10 cms

The wavelength of a radio signal is 200 metres. What is the frequency?

1.5 KHz
1.5 GHz
1.5 MHz
15 MHz

Frequency = Speed of Sound / Wavelength

= 3 x 10^8 / 200

= 1,500,000 or 1.5 MHz

The approximate ground waves of LF and MF are (by day) ___ and ___ respectively, with ___ suffering more from atmospheric attenuation.

1500nm; 1000nm; MF
1000nm; 500nm; LF
1000nm; 300nm; MF
500nm; 100nm; LF

The distance a surface wave can travel is limited by surface attenuation (which decreases at lower frequencies and over the sea). Surface waves are around:

100 NM long in the HF band.
500 NM long in the MF band.
1000 NM long in the LF band.
4000+ NM long in the VLF bands.

Surface waves and space waves occur together and the combination is called a ground wave. 

As the frequency of a transmitter is increased, the range of the ground wave will:

Decrease only at night
Increase only over the sea

A radio beacon has an operational range of 10 NM. By what factor should the transmitter power be increased in order to achieve an operational range of 20 NM?


If an NDB with a transmitter power of 25 KW which has a range of 50 nm is adjusted to give a power output of 100 KW the new range of the NDB will be approximately: "100 nm". 

An RMI indicates aircraft heading. To convert the RMI bearings of NDBs and VORs to true bearings the correct combination for the application of magnetic variation is: NDB: aircraft position, VOR: beacon position.

The speed of a radio wave in nm/sec is:


A radio wave with a horizontal magnetic component would be best received by a ___ aerial.


The question is about a horizontal magnetic component which means the electrical component is vertical.

Good luck,

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