Mcqs in Wave propagation

Mcqs in Wave propagation

A 'skip zone' is:
1. the distance between the antenna and where the refracted wave first returns to earth
2. the distance between the far end of the ground wave and where the refracted wave first returns to earth
3. the distance between any two refracted waves
4. a zone caused by lost sky waves
The medium which reflects high frequency radio waves back to the earth's surface is called the:
1. biosphere
2. stratosphere
3. ionosphere
4. troposphere
The highest frequency that will be reflected back to the earth at any given time is known as the:
1. UHF
2. MUF
3. OWF
4. LUF
All communications frequencies throughout the spectrum are affected in varying degrees by the:
1. atmospheric conditions
2. ionosphere
3. aurora borealis
4. sun
Solar cycles have an average length of:
1. 1 year
2. 3 years
3. 6 years
4. 11 years
The 'skywave' is another name for the:
1. ionospheric wave
2. tropospheric wave
3. ground wave
4. inverted wave
The polarisation of an electromagnetic wave is defined by the direction of:
1. the H field
2. propagation
3. the E field
4. the receiving antenna
That portion of HF radiation which is directly affected by the surface of the earth is called:
1. ionospheric wave
2. local field wave
3. ground wave
4. inverted wave
Radio wave energy on frequencies below 4 MHz during daylight hours is almost completely absorbed by this ionospheric layer:
1. C
2. D
3. E
4. F
Because of high absorption levels at frequencies below 4 MHz during daylight hours, only high angle signals are normally reflected back by this layer:
1. C
2. D
3. E
4. F
Scattered patches of high ionisation developed seasonally at the height of one of the layers is called:
1. sporadic-E
2. patchy
3. random reflectors
4. trans-equatorial ionisation
For long distance propagation, the radiation angle of energy from the antenna should be:
1. less than 30 degrees
2. more than 30 degrees but less than forty-five
3. more than 45 degrees but less than ninety
4. 90 degrees
The path radio waves normally follow from a transmitting antenna to a receiving antenna at VHF and higher frequencies is a:
1. circular path going north or south from the transmitter
2. great circle path
3. straight line
4. bent path via the ionosphere
A radio wave may follow two or more different paths during propagation and produce slowly-changing phase differences between signals at the receiver resulting in a phenomenon called:
1. absorption
2. baffling
3. fading
4. skip
The distance from the far end of the ground wave to the nearest point where the sky wave returns to the earth is called the:
1. skip distance
2. radiation distance
3. skip angle
4. skip zone
High Frequency long-distance propagation is most dependent on:
1. ionospheric reflection
2. tropospheric reflection
3. ground reflection
4. inverted reflection
The layer of the ionosphere mainly responsible for long distance communication is:
1. C
2. D
3. E
4. F
The ionisation level of the ionosphere reaches its minimum:
1. just after sunset
2. just before sunrise
3. at noon
4. at midnight
One of the ionospheric layers splits into two parts during the day called:
1. A & B
2. D1 & D2
3. E1 & E2
4. F1 & F2
Signal fadeouts resulting from an 'ionospheric storm' or 'sudden ionospheric disturbance' are usually attributed to:
1. heating of the ionised layers
2. over-use of the signal path
3. insufficient transmitted power
4. solar flare activity
The 80 metre band is useful for working:
1. in the summer at midday during high sunspot activity
2. long distance during daylight hours when absorption is not significant
3. all points on the earth's surface
4. up to several thousand kilometres in darkness but atmospheric and man-made noises tend to be high
The skip distance of radio signals is determined by the:
1. type of transmitting antenna used
2. power fed to the final amplifier of the transmitter
3. only the angle of radiation from the antenna
4. both the height of the ionosphere and the angle of radiation from the antenna
Three recognised layers of the ionosphere that affect radio propagation are:
1. A, E, F
2. B, D, E
3. C, E, F
4. D, E, F
Propagation on 80 metres during the summer daylight hours is limited to relatively short distances because of
1. high absorption in the D layer
2. the disappearance of the E layer
3. poor refraction by the F layer
4. pollution in the T layer
The distance from the transmitter to the nearest point where the sky wave returns to the earth is called the:
1. angle of radiation
2. maximum usable frequency
3. skip distance
4. skip zone
A variation in received signal strength caused by slowly changing differences in path lengths is called:
1. absorption
2. fading
3. fluctuation
4. path loss
VHF and UHF bands are frequently used for satellite communication because:
1. waves at these frequencies travel to and from the satellite relatively unaffected by the ionosphere
2. the Doppler frequency change caused by satellite motion is much less than at HF
3. satellites move too fast for HF waves to follow
4. the Doppler effect would cause HF waves to be shifted into the VHF and UHF bands.
The 'critical frequency' is defined as the:
1. highest frequency to which your transmitter can be tuned
2. lowest frequency which is reflected back to earth at vertical incidence
3. minimum usable frequency
4. highest frequency which will be reflected back to earth at vertical incidence
The speed of a radio wave:
1. varies indirectly to the frequency
2. is the same as the speed of light
3. is infinite in space
4. is always less than half the speed of light
The MUF for a given radio path is the:
1. mean of the maximum and minimum usable frequencies
2. maximum usable frequency
3. minimum usable frequency
4. mandatory usable frequency
The position of the E layer in the ionosphere is:
1. above the F layer
2. below the F layer
3. below the D layer
4. sporadic
A distant amplitude-modulated station is heard quite loudly but the modulation is at times severely distorted. A similar local station is not affected. The probable cause of this is:
1. transmitter malfunction
2. selective fading
3. a sudden ionospheric disturbance
4. front end overload
Skip distance is a term associated with signals through the ionosphere. Skip effects are due to:
1. reflection and refraction from the ionosphere
2. selective fading of local signals
3. high gain antennas being used
4. local cloud cover
The type of atmospheric layers which will best return signals to earth are:
1. oxidised layers
2. heavy cloud layers
3. ionised layers
4. sun spot layers
The ionosphere:
1. is a magnetised belt around the earth
2. consists of magnetised particles around the earth
3. is formed from layers of ionised gases around the earth
4. is a spherical belt of solar radiation around the earth
The skip distance of a sky wave will be greatest when the:
1. ionosphere is most densely ionised
2. signal given out is strongest
3. angle of radiation is smallest
4. polarisation is vertical
If the height of the reflecting layer of the ionosphere increases, the skip distance of a high frequency transmission:
1. stays the same
2. decreases
3. varies regularly
4. becomes greater
If the frequency of a transmitted signal is so high that we no longer receive a reflection from the ionosphere, the signal frequency is above the:
1. speed of light
2. sun spot frequency
3. skip distance
4. maximum usable frequency
A 'line of sight' transmission between two stations uses mainly the:
1. ionosphere
2. troposphere
3. sky wave
4. ground wave
The distance travelled by ground waves in air:
1. is the same for all frequencies
2. is less at higher frequencies
3. is more at higher frequencies
4. depends on the maximum usable frequency
The radio wave from the transmitter to the ionosphere and back to earth is correctly known as the:
1. sky wave
2. skip wave
3. surface wave
4. F layer
Reception of high frequency radio waves beyond 4000 km normally occurs by the:
1. ground wave
2. skip wave
3. surface wave
4. sky wave
A 28 MHz radio signal is more likely to be heard over great distances:
1. if the transmitter power is reduced
2. during daylight hours
3. only during the night
4. at full moon
The number of high frequency bands open to long distance communication at any time depends on:
1. the highest frequency at which ionospheric reflection can occur
2. the number of frequencies the receiver can tune
3. the power being radiated by the transmitting station
4. the height of the transmitting antenna
Regular changes in the ionosphere occur approximately every 11:
1. days
2. months
3. years
4. centuries
When a HF transmitted radio signal reaches a receiver, small changes in the ionosphere can cause:
1. consistently stronger signals
2. a change in the ground wave signal
3. variations in signal strength
4. consistently weaker signals
The usual effect of ionospheric storms is to:
1. increase the maximum usable frequency
2. cause a fade-out of sky-wave signals
3. produce extreme weather changes
4. prevent communications by ground wave
Changes in received signal strength when sky wave propagation is used are called:
1. ground wave losses
2. modulation losses
3. fading
4. sunspots
Although high frequency signals may be received from a distant station by a sky wave at a certain time, it may not be possible to hear them an hour later. This may be due to:
1. changes in the ionosphere
2. shading of the earth by clouds
3. changes in atmospheric temperature
4. absorption of the ground wave signal
VHF or UHF signals transmitted towards a tall building are often received at a more distant point in another direction because:
1. these waves are easily bent by the ionosphere
2. these waves are easily reflected by objects in their path
3. you can never tell in which direction a wave is travelling
4. tall buildings have elevators