RF Energy Propagation and Wave Fronts

Questions and Answers

What degree does the signal detected by receiver R1 lead the reference signal?

90°

180°

270° (correct)

360°

How does the signal detected by receiver R2 differ from that of receiver R1?

It is a lower frequency signal.

It leads the reference signal by 270°.

It lacks variability.

It leads the reference signal by 180°. (correct)

What is assumed about the distance from the antenna array to the aircraft receivers?

It is equal to the diameter of the array.

It is significantly smaller than the diameter of the array.

It is significantly larger than the diameter of the array. (correct)

It varies depending on the aircraft type.

What is the rotational direction of antenna A with respect to antenna M?

Counterclockwise Signup and view all the answers

What is the primary type of signal that the DVOR station initially radiates from the northernmost point of the array?

Upper sideband signal Signup and view all the answers

What does the vector representation in Figure 2-5 illustrate?

The FM and AM phase relationship at various points Signup and view all the answers

Which receivers are specifically illustrated in the context of a DVOR station?

Receivers A, B, C, and D Signup and view all the answers

What phase relationship is observed as the antenna array commutes?

Variable phase relationship Signup and view all the answers

What is the relationship between distance and time for RF signals as they propagate?

Distance can be equated to time since signals propagate through space. Signup and view all the answers

Which antenna produces a lower Doppler shifted frequency compared to the fundamental frequency?

Western antenna Signup and view all the answers

What effect does the counterclockwise rotation of sideband radiating elements have on signal frequency?

It produces varying frequency shifts based on antenna position. Signup and view all the answers

How is frequency defined in the context of signal propagation?

Frequency is the reciprocal of time. Signup and view all the answers

What happens to the frequency produced by the eastern antenna?

It is increased by 480 Hz. Signup and view all the answers

What measurement is utilized to determine the separation of wave fronts from antennas?

Distance measurement over time Signup and view all the answers

Which antennas produce no frequency shift according to the given information?

Northern and southern antennas Signup and view all the answers

What is the significance of the measurement distance d1 and d2 in the context?

d1 is greater than d2. Signup and view all the answers

What is the phase relationship between the detected FM signal and the reference AM signal for aircraft receiver D?

The FM signal leads the reference by one-quarter cycle. Signup and view all the answers

At what bearing does aircraft receiver C detect the variable FM signal leading the reference by 180°?

180° Signup and view all the answers

Which combination of antennas results in no Doppler shift being present?

North and South antennas. Signup and view all the answers

How much time separates the emissions of RF energy from antennas #12 and #13 during the counterclockwise rotation?

1/1440 of a second. Signup and view all the answers

What is the angular relationship between the detected FM signal of receiver B and its reference signal?

It leads by three-fourths cycle. Signup and view all the answers

What type of signal does aircraft receiver A detect that is identical across all receivers?

A 30 Hz reference AM signal. Signup and view all the answers

What phenomenon is described as being most pronounced when the West and East antennas are radiating?

Doppler shift. Signup and view all the answers

What does the variable FM subcarrier detected in aircraft receiver A serve to represent?

A 30 Hz FM variable signal. Signup and view all the answers

Study Notes

RF Energy and Antenna Operation

Antenna #37 starts radiating RF energy 1/1440 of a second after antenna #12 and #13.
The separation of wave fronts from these antennas is defined as distance d2, with d1 observed to be greater than d2.
Signal propagation relates distance separation to time; frequency (f) is the reciprocal of time (1/t).

Doppler Shift Mechanism

The western antenna produces a Doppler-shifted frequency of 9480 Hz (9960 Hz - 480 Hz).
The eastern antenna shifts frequency to 10440 Hz (9960 Hz + 480 Hz).
Northern and southern antennas do not produce frequency shifts.

Aircraft Receiver Detection

Aircraft receiver A detects a 30 Hz FM subcarrier and outputs a 30 Hz reference signal identical to other receivers (B, C, D).
Aircraft receiver D, at a 90° bearing, leads the reference signal by 90°; C leads by 180° at a 180° bearing; B leads by 270° at a 270° bearing.
Aircraft receiver A at 0° has signals in phase.

Azimuth-Dependent FM Generation

The azimuth-dependent FM generation is reliant on the configuration of antennas around the DVOR station.
Antenna A rotates counterclockwise around a reference antenna M, impacting the variable signal detection by receivers R1 and R2.

Array Commutation and Phase Relationships

After a quarter cycle of commutation, the antenna returns to its northern position, repeating the cycle.
The distances from antennas A (sideband) and M (reference) to aircraft receivers are assumed substantially larger than the array's diameter.
At the start of antenna operation, the upper sideband signal is emitted, but the lower sideband is similar in characteristics.

Visual Illustrations

Figures referenced illustrate the instantaneous direction of RF sources, received signals, and vector representations of phase relationships at various positions in relation to the DVOR station.

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Description

This quiz explores the concepts of RF energy propagation and the behavior of wave fronts produced by antennas. It focuses on the relationship between signal separation distances and frequencies, highlighting how antenna timing impacts wavefront measurements.