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Subel. K
6 questions
Subelement K
Aircraft
Section 71
Automatic Direction Finding Equipment (ADF) & Transponders
What is the frequency range of an aircraft’s Automatic Direction Finding (ADF) equipment?
  • Correct Answer
    190 kHz to 1750 kHz.
  • 190 MHz to 1750 MHz.
  • 108.10 MHz to 111.95 MHz.
  • 108.00 MHz to 117.95 MHz.

What is the frequency range of an aircraft’s Automatic Direction Finding (ADF) equipment?

190 kHz to 1750 kHz.

See Wikipedia's article on Automatic direction finder

For more information, please see Aeronautics Guide for the article on Aircraft Automatic Direction Finder (ADF)

Also, see YouTube video Rohde Schwarz channel, for the video called Understanding ADF and
from the Doofer911 channel video called FSX Tutorial: Automatic Direction Finder (ADF)

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What is meant by the term “night effect” when using an aircraft’s Automatic Direction Finding (ADF) equipment? Night effect refers to the fact that:
  • All Non Directional Beacon (NDB) transmitters are turned-off at dusk and turned-on at dawn.
  • Correct Answer
    Non Directional Beacon (NDB) transmissions can bounce-off the Earth’s ionosphere at night and be received at almost any direction.
  • An aircraft’s ADF transmissions will be slowed at night due to the increased density of the Earth’s atmosphere after sunset.
  • An aircraft’s ADF antennas usually collect dew moisture after sunset which decreases their effective reception distance from an NDB transmitter.

What is meant by the term “night effect” when using an aircraft’s Automatic Direction Finding (ADF) equipment? Night effect refers to the fact that:

Non Directional Beacon (NDB) transmissions can bounce-off the Earth’s ionosphere at night and be received at almost any direction.

See Wikipedia's article on Automatic direction finder

For more information, please see Aeronautics Guide for the article on Aircraft Automatic Direction Finder (ADF)

Also, see YouTube video Rohde Schwarz channel, for the video called Understanding ADF and
from the Doofer911 channel video called FSX Tutorial: Automatic Direction Finder (ADF)

REFERENCE: Pilots Handbook of Aeronautical Knowledge Chapter 15 Navigation, well-illustrated pdf document.

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What are the transmit and receive frequencies of an aircraft’s mode C transponder operating in the Air Traffic Control RADAR Beacon System (ATCRBS)?
  • Correct Answer
    Transmit at 1090 MHz, and receive at 1030 MHz
  • Transmit at 1030 kHz, and receive at 1090 kHz
  • Transmit at 1090 kHz, and receive at 1030 kHz
  • Transmit at 1030 MHz, and receive at 1090 MHz

What are the transmit and receive frequencies of an aircraft’s mode C transponder operating in the Air Traffic Control RADAR Beacon System (ATCRBS)?

Transmit at 1090 MHz, and receive at 1030 MHz

This is a tricky question. It asks about frequencies from the aircraft's point, not that of the station transponder, so the function and frequencies are reversed. Just remember the answer.

The Code of Federal Regulations, Title 14 Chapter I Subchapter C Part 43 Appendix F to Part 43 - ATC Transponder Tests and Inspections, in the paragraph 14 CFR Appendix F to Part 43(a)

Radio Reply Frequency:

(1) For all classes of ATCRBS transponders, interrogate the transponder and verify that the reply frequency is 1090 ±3 Megahertz (MHz).

From Wikipedia's article on Air traffic control radar beacon system

"The steps involved in performing an ATCRBS interrogation are as follows:

First, the ATCRBS interrogator periodically interrogates aircraft on a frequency of 1030 MHz.

When the aircraft receives the interrogation, the aircraft transponder will send a reply on 1090 MHz after a 3.0 μs delay indicating the requested information. "

For more information, please see Flight Literacy site for the article on Air Traffic Control (ATC) Services

For live radar flight information, please see Flightradar 24 site for Airplane Flight Graphical Information.

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In addition to duplicating the functions of a mode C transponder, an aircraft’s mode S transponder can also provide:
  • Primary RADAR surveillance capabilities.
  • Long range lightning detection.
  • Correct Answer
    Mid-Air collision avoidance capabilities.
  • Backup VHF voice communication abilities.

In addition to duplicating the functions of a mode C transponder, an aircraft’s mode S transponder can also provide:

Mid-Air collision avoidance capabilities.

For more information, see Sky Brary site for the article Transponder

See Cfinotebook site for the article Aircraft Transponder

Also, from site Flying, please see the article Everything You Need to Know about Mode C Transponders

Please see FAA article The Mode S Team

Also, please view the YouTube video from Terry y channel called Mode S

Please see pdf presentation from the Offutt Air Force Base called Mid-Air Collision Avoidance Guide

See the AOPA site for the article called Avoiding Midair Collisions

Also, see the FAA document P-8740-51 How to Avoid a Mid Air Collision

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What type of encoding is used in an aircraft’s mode C transponder transmission to a ground station of the Air Traffic Control RADAR Beacon System (ATCRBS)?
  • Differential phase shift keying.
  • Correct Answer
    Pulse position modulation.
  • Doppler effect compressional encryption.
  • Amplitude modulation at 95%.

What type of encoding is used in an aircraft’s mode C transponder transmission to a ground station of the Air Traffic Control RADAR Beacon System (ATCRBS)?

Pulse position modulation.

See Wikipedia's article on Pulse-position modulation

View YouTube video from WIT Solapur - Professional Learning Community channel called Pulse Position Modulation

For more information, see Sky Brary site for the article Transponder

See Cfinotebook site for the article Aircraft Transponder

Also, from site Flying, please see the article Everything You Need to Know about Mode C Transponders

For more information, please see Wikipedia's article Air traffic control radar beacon system

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Choose the only correct statement about an aircraft’s Automatic Direction Finding (ADF) equipment.
  • An aircraft’s ADF transmission exhibits primarily a line-of-sight range to the ground-based target station and will not follow the curvature of the Earth.
  • Only a single omnidirectional sense antenna is required to receive an NDB transmission and process the signal to calculate the aircraft’s bearing to the selected ground station.
  • All frequencies in the ADF’s operating range except the commercial standard broadcast stations (550 to 1660 kHz) can be utilized as a navigational Non Directional Beacon (NDB) signal.
  • Correct Answer
    An aircraft’s ADF antennas can receive transmissions that are over the Earth’s horizon (sometimes several hundred miles away) since these signals will follow the curvature of the Earth.

Choose the only correct statement about an aircraft’s Automatic Direction Finding (ADF) equipment.

An aircraft’s ADF antennas can receive transmissions that are over the Earth’s horizon (sometimes several hundred miles away) since these signals will follow the curvature of the Earth.

See Wikipedia's articles Direction finding and on Automatic direction finder

For more information, please see Aeronautics Guide for the article on Aircraft Automatic Direction Finder (ADF)

Also, see YouTube video Rohde Schwarz channel, for the video called Understanding ADF and
from the Doofer911 channel video called FSX Tutorial: Automatic Direction Finder (ADF)

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