A-007-07: Ground and elevation effects, vertical radiation (take off) angle
A-007-07-01:
For a 3-element Yagi antenna with horizontally mounted elements, how does the main lobe takeoff angle vary with height above flat ground?
It decreases with increasing height
It increases with increasing height
It does not vary with height
It depends on E-region height, not antenna height
A-007-07-02:
Most simple horizontally polarized antennas do not exhibit any directivity unless they are:
a half wavelength or more above the ground
an eighth of a wavelength above the ground
a quarter wavelength above the ground
three-eighths of a wavelength above the ground
A-007-07-03:
The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:
several centimeters to as much as 2 meters below ground, depending upon soil conditions
as much as 6 cm below ground depending upon soil conditions
as much as a meter above ground
at ground level exactly
A-007-07-04:
Why is a ground-mounted vertical quarter-wave antenna in reasonably open surroundings better for long distance contacts than a half-wave dipole at a quarter wavelength above ground?
The vertical radiation angle is lower
The radiation resistance is lower
It has an omnidirectional characteristic
It uses vertical polarization
A-007-07-05:
When a half-wave dipole antenna is installed one-half wavelength above ground, the:
vertical or upward radiation is cancelled
radiation pattern changes to produce side lobes at 15 and 50 degrees
side lobe radiation is cancelled
radiation pattern is unaffected
A-007-07-06:
How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?
If the antenna is less than one-half wavelength high, reflected radio waves from the ground significantly distort the pattern
Antenna height has no effect on the pattern
If the antenna is less than one-half wavelength high, radiation off the ends of the wire is eliminated
If the antenna is too high, the pattern becomes unpredictable
A-007-07-07:
For long distance propagation, the vertical radiation angle of the energy from the antenna should be:
less than 30 degrees
more than 45 degrees but less than 90 degrees
90 degrees
more than 30 degrees but less than 45 degrees
A-007-07-08:
Greater distance can be covered with multiple-hop transmissions by decreasing the:
vertical radiation angle of the antenna
power applied to the antenna
main height of the antenna
length of the antenna
A-007-07-09:
The impedance at the centre of a dipole antenna more than 3 wavelengths above ground would be nearest to:
75 ohms
25 ohms
300 ohms
600 ohms
A-007-07-10:
What is the main reason why so many VHF base and mobile antennas are 5/8 of a wavelength?
Most of the energy is radiated at a low angle
The angle of radiation is high giving excellent local coverage
It's easy to match the antenna to the transmitter
It's a convenient length on VHF
A-007-07-11:
The most important consideration when deciding upon an antenna for contacting stations at great distances (DX) is:
vertical angle of radiation
sunspot activity
impedance
bandwidth
|
Color key:
|
|
● = Unseen
|
|
● = Weak
|
|
● = Review
|
|
● = Learned
|
|
● = Incorrect answer
|
