E9H Receiving antennas: radio direction finding (RDF) techniques; Beverage antennas; single- and multiple-turn loops
- E9H01 (D)
When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency? #card
- A. Its overall length must not exceed 1/4 wavelength
- B. It must be mounted more than 1 wavelength above ground
- C. It should be configured as a four-sided loop
- D. It should be at least one wavelength long
- E9H02 (A)
Which is generally true for 160- and 80-meter receiving antennas? #card
- A. Atmospheric noise is so high that directivity is much more important than losses
- B. They must be erected at least 1/2 wavelength above the ground to attain good directivity
- C. Low loss coax transmission line is essential for good performance
- D. All these choices are correct
- E9H03 (D)
What is receiving directivity factor (RDF)? #card
- A. Forward gain compared to the gain in the reverse direction
- B. Relative directivity compared to isotropic
- C. Relative directivity compared to a dipole
- D. Peak antenna gain compared to average gain over the hemisphere around and above the antenna
- E9H04 (B)
What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna? #card
- A. It adds capacitive loading, increasing the bandwidth of the antenna
- B. It eliminates unbalanced capacitive coupling to the antenna’s surroundings, improving the depth of its nulls
- C. It eliminates tracking errors caused by strong out-of-band signals
- D. It increases signal strength by providing a better match to the feed line
- E9H05 (A)
What challenge is presented by a small wire-loop antenna for direction finding? #card
- A. It has a bidirectional null pattern
- B. It does not have a clearly defined null
- C. It is practical for use only on VHF and higher bands
- D. All these choices are correct
- E9H06 (D)
What indicates the correct value of terminating resistance for a Beverage antenna? #card
- A. Maximum feed point DC resistance at the center of the desired frequency range
- B. Minimum low-angle front-to-back ratio at the design frequency
- C. Maximum DC current in the terminating resistor
- D. Minimum variation in SWR over the desired frequency range
- E9H07 (B)
What is the function of a Beverage antenna’s termination resistor? #card
- A. Increase the front-to-side ratio
- B. Absorb signals from the reverse direction
- C. Decrease SWR bandwidth
- D. Eliminate harmonic reception
- E9H08 (A)
What is the function of a sense antenna? #card
- A. It modifies the pattern of a DF antenna to provide a null in only one direction
- B. It increases the sensitivity of a DF antenna array
- C. It allows DF antennas to receive signals at different vertical angles
- D. It provides diversity reception that cancels multipath signals
- E9H09 (A)
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna? #card
- A. Cardioid
- B. Bidirectional
- C. Omnidirectional
- D. Hyperbolic
- E9H10 (C)
How can the output voltage of a multiple-turn receiving loop antenna be increased? #card
- A. By reducing the permeability of the loop shield
- B. By utilizing high impedance wire for the coupling loop
- C. By increasing the number of turns and/or the area enclosed by the loop
- D. All these choices are correct
- E9H11 (B)
What feature of a cardioid pattern antenna makes it useful for direction-finding antennas? #card
- A. A very sharp peak
- B. A single null
- C. Broadband response
- D. High radiation angle
