Electronic Navigation (ENAV)
ENAV - ELECTRONIC NAVIGATION | EXAM QUESTIONS AND CORRECT
ANSWERS | VERIFIED MARITIME ELECTRONIC NAVIGATION LATEST
2026/2027
ELECTRONIC NAVIGATION (ENAV)
1. Marine radar determines the range of a target by measuring:
A. The Doppler shift of the returned signal
B. The strength of the returned echo
C. The phase difference between two antennas
D. The elapsed time between transmission of a pulse and reception of its
echo
D. The elapsed time between transmission of a pulse and reception
of its echo
Radio energy travels at a known speed, so half the round-trip time
multiplied by that speed gives the range.
2. A marine radar operating in the X-band uses a wavelength of
approximately:
A. 30 cm
B. 10 cm
C. 1 cm
D. 3 cm
D. 3 cm
X-band radars work near 9.4 GHz, which corresponds to a wavelength of
about 3 cm.
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, Electronic Navigation (ENAV)
3. Compared with an X-band radar, an S-band radar generally:
A. Detects small targets at close range more readily
B. Uses a shorter wavelength
C. Gives sharper bearing discrimination for the same antenna length
D. Performs better in heavy rain and sea clutter
D. Performs better in heavy rain and sea clutter
The longer 10 cm wavelength of S-band is attenuated and scattered less
by rain and waves.
4. Bearing discrimination on a radar is mainly determined by:
A. Pulse repetition frequency
B. Vertical beam width
C. Pulse length
D. Horizontal beam width
D. Horizontal beam width
A narrow horizontal beam separates two targets at the same range but on
slightly different bearings.
5. Range discrimination on a radar is mainly determined by:
A. Horizontal beam width
B. Pulse length
C. Antenna rotation rate
D. Vertical beam width
B. Pulse length
Two targets on the same bearing appear separate only if they are more
than half a pulse length apart.
6. The horizontal beam width of a radar antenna becomes narrower
when:
A. The PRF is increased
B. The pulse length is shortened
C. The antenna length is increased
D. The transmitter power is reduced
C. The antenna length is increased
Beam width is inversely related to antenna aperture, so a longer scanner
produces a narrower beam.
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, Electronic Navigation (ENAV)
7. Switching to a longer pulse length on a radar will generally:
A. Improve range discrimination and minimum range
B. Reduce the effect of sea clutter
C. Narrow the horizontal beam width
D. Increase detection range but reduce range discrimination
D. Increase detection range but reduce range discrimination
A longer pulse carries more energy for distant targets but blurs echoes
that are close together in range.
8. The minimum detection range of a radar is chiefly limited by:
A. Antenna height alone
B. Pulse length and the recovery time of the receiver
C. The gain setting
D. Horizontal beam width
B. Pulse length and the recovery time of the receiver
The receiver cannot process echoes that return while the pulse is still
being transmitted or the TR cell is recovering.
9. Pulse repetition frequency (PRF) primarily limits:
A. The maximum unambiguous range
B. The vertical beam width
C. The bearing accuracy
D. The radar horizon
A. The maximum unambiguous range
Each echo must return before the next pulse is sent, so a high PRF
reduces the longest range that can be displayed without ambiguity.
10. The radar horizon is typically about how much farther than the
visible horizon under standard conditions?
A. Exactly the same distance
B. About 50 percent
C. About 6 percent
D. About 25 percent
C. About 6 percent
Radar waves bend slightly more than light in a standard atmosphere,
giving a horizon roughly 6 percent beyond the geographic one.
Page 3 of 51
, Electronic Navigation (ENAV)
11. The approximate radar horizon in nautical miles for an antenna
height h in metres is given by:
A. 1.17 × √h
B. 3.5 × √h
C. 2.2 × √h
D. 0.5 × h
C. 2.2 × √h
The standard formula 2.2√h (h in metres) accounts for normal
atmospheric refraction of radar energy.
12. Super-refraction (ducting) is most likely to cause a radar to:
A. Detect targets at abnormally long ranges
B. Lose all targets beyond one mile
C. Display permanent side lobes
D. Show targets on a reciprocal bearing
A. Detect targets at abnormally long ranges
A temperature inversion bends the beam toward the surface, trapping
energy and extending detection range.
13. Sub-refraction is associated with which atmospheric condition?
A. Warm dry air over a cold sea
B. Stable fog conditions
C. A strong temperature inversion
D. Cold air lying over warmer sea with rapidly increasing humidity aloft
D. Cold air lying over warmer sea with rapidly increasing humidity
aloft
When cold air is over warm water the beam bends upward, shortening
the effective radar range.
14. The sea clutter (STC/anti-clutter sea) control works by:
A. Changing the transmitted frequency
B. Differentiating the leading edge of every echo
C. Reducing receiver gain at short ranges and gradually restoring it with
range
D. Reducing gain uniformly over the whole screen
C. Reducing receiver gain at short ranges and gradually restoring it
with range
Sensitivity Time Control suppresses the strong close-range wave returns
while leaving distant echoes unaffected.
Page 4 of 51
ENAV - ELECTRONIC NAVIGATION | EXAM QUESTIONS AND CORRECT
ANSWERS | VERIFIED MARITIME ELECTRONIC NAVIGATION LATEST
2026/2027
ELECTRONIC NAVIGATION (ENAV)
1. Marine radar determines the range of a target by measuring:
A. The Doppler shift of the returned signal
B. The strength of the returned echo
C. The phase difference between two antennas
D. The elapsed time between transmission of a pulse and reception of its
echo
D. The elapsed time between transmission of a pulse and reception
of its echo
Radio energy travels at a known speed, so half the round-trip time
multiplied by that speed gives the range.
2. A marine radar operating in the X-band uses a wavelength of
approximately:
A. 30 cm
B. 10 cm
C. 1 cm
D. 3 cm
D. 3 cm
X-band radars work near 9.4 GHz, which corresponds to a wavelength of
about 3 cm.
Page 1 of 51
, Electronic Navigation (ENAV)
3. Compared with an X-band radar, an S-band radar generally:
A. Detects small targets at close range more readily
B. Uses a shorter wavelength
C. Gives sharper bearing discrimination for the same antenna length
D. Performs better in heavy rain and sea clutter
D. Performs better in heavy rain and sea clutter
The longer 10 cm wavelength of S-band is attenuated and scattered less
by rain and waves.
4. Bearing discrimination on a radar is mainly determined by:
A. Pulse repetition frequency
B. Vertical beam width
C. Pulse length
D. Horizontal beam width
D. Horizontal beam width
A narrow horizontal beam separates two targets at the same range but on
slightly different bearings.
5. Range discrimination on a radar is mainly determined by:
A. Horizontal beam width
B. Pulse length
C. Antenna rotation rate
D. Vertical beam width
B. Pulse length
Two targets on the same bearing appear separate only if they are more
than half a pulse length apart.
6. The horizontal beam width of a radar antenna becomes narrower
when:
A. The PRF is increased
B. The pulse length is shortened
C. The antenna length is increased
D. The transmitter power is reduced
C. The antenna length is increased
Beam width is inversely related to antenna aperture, so a longer scanner
produces a narrower beam.
Page 2 of 51
, Electronic Navigation (ENAV)
7. Switching to a longer pulse length on a radar will generally:
A. Improve range discrimination and minimum range
B. Reduce the effect of sea clutter
C. Narrow the horizontal beam width
D. Increase detection range but reduce range discrimination
D. Increase detection range but reduce range discrimination
A longer pulse carries more energy for distant targets but blurs echoes
that are close together in range.
8. The minimum detection range of a radar is chiefly limited by:
A. Antenna height alone
B. Pulse length and the recovery time of the receiver
C. The gain setting
D. Horizontal beam width
B. Pulse length and the recovery time of the receiver
The receiver cannot process echoes that return while the pulse is still
being transmitted or the TR cell is recovering.
9. Pulse repetition frequency (PRF) primarily limits:
A. The maximum unambiguous range
B. The vertical beam width
C. The bearing accuracy
D. The radar horizon
A. The maximum unambiguous range
Each echo must return before the next pulse is sent, so a high PRF
reduces the longest range that can be displayed without ambiguity.
10. The radar horizon is typically about how much farther than the
visible horizon under standard conditions?
A. Exactly the same distance
B. About 50 percent
C. About 6 percent
D. About 25 percent
C. About 6 percent
Radar waves bend slightly more than light in a standard atmosphere,
giving a horizon roughly 6 percent beyond the geographic one.
Page 3 of 51
, Electronic Navigation (ENAV)
11. The approximate radar horizon in nautical miles for an antenna
height h in metres is given by:
A. 1.17 × √h
B. 3.5 × √h
C. 2.2 × √h
D. 0.5 × h
C. 2.2 × √h
The standard formula 2.2√h (h in metres) accounts for normal
atmospheric refraction of radar energy.
12. Super-refraction (ducting) is most likely to cause a radar to:
A. Detect targets at abnormally long ranges
B. Lose all targets beyond one mile
C. Display permanent side lobes
D. Show targets on a reciprocal bearing
A. Detect targets at abnormally long ranges
A temperature inversion bends the beam toward the surface, trapping
energy and extending detection range.
13. Sub-refraction is associated with which atmospheric condition?
A. Warm dry air over a cold sea
B. Stable fog conditions
C. A strong temperature inversion
D. Cold air lying over warmer sea with rapidly increasing humidity aloft
D. Cold air lying over warmer sea with rapidly increasing humidity
aloft
When cold air is over warm water the beam bends upward, shortening
the effective radar range.
14. The sea clutter (STC/anti-clutter sea) control works by:
A. Changing the transmitted frequency
B. Differentiating the leading edge of every echo
C. Reducing receiver gain at short ranges and gradually restoring it with
range
D. Reducing gain uniformly over the whole screen
C. Reducing receiver gain at short ranges and gradually restoring it
with range
Sensitivity Time Control suppresses the strong close-range wave returns
while leaving distant echoes unaffected.
Page 4 of 51
