2016-E9H: Receiving Antennas: radio direction finding antennas; Beverage Antennas; specialized receiving antennas; longwire receiving antennas
When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?
It should be one or more wavelengths long
Its overall length must not exceed 1/4 wavelength
It must be mounted more than 1 wavelength above ground
It should be configured as a four-sided loop
Which is generally true for low band (160 meter and 80 meter) receiving antennas?
Atmospheric noise is so high that gain over a dipole is not important
They must be erected at least 1/2 wavelength above the ground to attain good directivity
Low loss coax transmission line is essential for good performance
All of these choices are correct
What is an advantage of using a shielded loop antenna for direction finding?
It is electro statically balanced against ground, giving better nulls
It automatically cancels ignition noise in mobile installations
It eliminates tracking errors caused by strong out-of-band signals
It allows stations to communicate without giving away their position
What is the main drawback of a wire-loop antenna for direction finding?
It has a bidirectional pattern
It is non-rotatable
It receives equally well in all directions
It is practical for use only on VHF bands
What is the triangulation method of direction finding?
Antenna headings from several different receiving locations are used to locate the signal source
The geometric angles of sky waves from the source are used to determine its position
A fixed receiving station plots three headings to the signal source
A fixed receiving station uses three different antennas to plot the location of the signal source
Why is it advisable to use an RF attenuator on a receiver being used for direction finding?
It prevents receiver overload which could make it difficult to determine peaks or nulls
It narrows the bandwidth of the received signal to improve signal to noise ratio
It compensates for the effects of an isotropic antenna, thereby improving directivity
It reduces loss of received signals caused by antenna pattern nulls, thereby increasing sensitivity
What is the function of a sense antenna?
It modifies the pattern of a DF antenna array to provide a null in one direction
It increases the sensitivity of a DF antenna array
It allows DF antennas to receive signals at different vertical angles
It provides diversity reception that cancels multipath signals
Which of the following describes the construction of a receiving loop antenna?
One or more turns of wire wound in the shape of a large open coil
A large circularly polarized antenna
A small coil of wire tightly wound around a toroidal ferrite core
A vertical antenna coupled to a feed line through an inductive loop of wire
How can the output voltage of a multiple turn receiving loop antenna be increased?
By increasing either the number of wire turns in the loop or the area of the loop structure or both
By reducing the permeability of the loop shield
By increasing the number of wire turns in the loop and reducing the area of the loop structure
By winding adjacent turns in opposing directions
What characteristic of a cardioid pattern antenna is useful for direction finding?
A very sharp single null
A very sharp peak
Broad band response
● = Unseen
● = Weak
● = Review
● = Learned
● = Incorrect answer