Amateur Extra E9H: Receiving and direction-finding antennas
These are the 11 official questions in group E9H of the 2024–2028 Amateur Extra question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- E9H01Question 1
When constructing a Beverage antenna, which of the following factors should be included in the design to achieve good performance at the desired frequency?
- AIts overall length must not exceed 1/4 wavelength
- BIt must be mounted more than 1 wavelength above ground
- CIt should be configured as a four-sided loop
- DIt should be at least one wavelength long Correct
Why: A Beverage should be at least one wavelength long.
- E9H02Question 2
Which is generally true for 160- and 80-meter receiving antennas?
- AAtmospheric noise is so high that directivity is much more important than losses Correct
- BThey must be erected at least 1/2 wavelength above the ground to attain good directivity
- CLow loss coax transmission line is essential for good performance
- DAll these choices are correct
Why: On 160 and 80 m, atmospheric noise makes directivity matter more than losses.
- E9H03Question 3
What is receiving directivity factor (RDF)?
- AForward gain compared to the gain in the reverse direction
- BRelative directivity compared to isotropic
- CRelative directivity compared to a dipole
- DPeak antenna gain compared to average gain over the hemisphere around and above the antenna Correct
Why: RDF compares peak gain with average gain over the hemisphere.
- E9H04Question 4
What is the purpose of placing an electrostatic shield around a small-loop direction-finding antenna?
- AIt adds capacitive loading, increasing the bandwidth of the antenna
- BIt eliminates unbalanced capacitive coupling to the antenna’s surroundings, improving the depth of its nulls Correct
- CIt eliminates tracking errors caused by strong out-of-band signals
- DIt increases signal strength by providing a better match to the feed line
Why: The shield removes unbalanced capacitive coupling, deepening the nulls.
- E9H05Question 5
What challenge is presented by a small wire-loop antenna for direction finding?
- AIt has a bidirectional null pattern Correct
- BIt does not have a clearly defined null
- CIt is practical for use only on VHF and higher bands
- DAll these choices are correct
Why: A small loop has two nulls, so direction is ambiguous.
- E9H06Question 6
What indicates the correct value of terminating resistance for a Beverage antenna?
- AMaximum feed point DC resistance at the center of the desired frequency range
- BMinimum low-angle front-to-back ratio at the design frequency
- CMaximum DC current in the terminating resistor
- DMinimum variation in SWR over the desired frequency range Correct
Why: The right termination gives the least SWR variation across the band.
- E9H07Question 7
What is the function of a Beverage antenna’s termination resistor?
- AIncrease the front-to-side ratio
- BAbsorb signals from the reverse direction Correct
- CDecrease SWR bandwidth
- DEliminate harmonic reception
Why: The termination resistor absorbs signals from the reverse direction.
- E9H08Question 8
What is the function of a sense antenna?
- AIt modifies the pattern of a DF antenna to provide a null in only one direction Correct
- BIt increases the sensitivity of a DF antenna array
- CIt allows DF antennas to receive signals at different vertical angles
- DIt provides diversity reception that cancels multipath signals
Why: A sense antenna leaves a null in only one direction.
- E9H09Question 9
What type of radiation pattern is created by a single-turn, terminated loop such as a pennant antenna?
- ACardioid Correct
- BBidirectional
- COmnidirectional
- DHyperbolic
Why: A terminated single-turn loop like a pennant has a cardioid pattern.
- E9H10Question 10
How can the output voltage of a multiple-turn receiving loop antenna be increased?
- ABy reducing the permeability of the loop shield
- BBy utilizing high impedance wire for the coupling loop
- CBy increasing the number of turns and/or the area enclosed by the loop Correct
- DAll these choices are correct
Why: More turns or more loop area raise the output voltage.
- E9H11Question 11
What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?
- AA very sharp peak
- BA single null Correct
- CBroadband response
- DHigh radiation angle
Why: A cardioid's single null makes direction finding unambiguous.