HF Antenna Types and Locations
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HF Antenna Types and Locations

This quiz covers various types of HF antennas and their locations on an aircraft, including long wire, stinger, integrated, and towel bar antennas. It also discusses HF communication dos and don'ts.

Created by
@HolyBambooFlute

Questions and Answers

Where is the Long Wire antenna typically located?

Top of the fuselage

What is the purpose of SELCAL?

To alert the flight crew of a specific radio call

Which of the following frequencies is a TX restricted frequency?

2.5 MHz

What is the transmission sequence of the SELCAL encoder?

<p>2 groups of 2 tones each</p> Signup and view all the answers

What is the duty cycle of the HF transmitter?

<p>1 minute on, 4 minutes off</p> Signup and view all the answers

What is the purpose of the Towel Bar antenna?

<p>To provide HF communication</p> Signup and view all the answers

What is the frequency spectrum of the VHF Comm system?

<p>118.00 – 135.975 MHz</p> Signup and view all the answers

What is the primary purpose of SELCAL operation?

<p>To select and call aircraft</p> Signup and view all the answers

How do radio waves propagate from point A to point B?

<p>Through the air using electromagnetic waves</p> Signup and view all the answers

What is the characteristic of a half-duplex system?

<p>Signal can be transmitted in both directions but not simultaneously</p> Signup and view all the answers

What type of antenna configuration is typically used for VHF Comm?

<p>Omni-directional antenna</p> Signup and view all the answers

What is the frequency spectrum of the HF Comm system?

<p>2.00 – 29.995 MHz</p> Signup and view all the answers

What is the primary purpose of a ground plane in an aircraft antenna?

<p>To increase the gain of the antenna</p> Signup and view all the answers

Why is painting antennas with aircraft paint not recommended?

<p>It can de-tune the antenna</p> Signup and view all the answers

What is the frequency range of the VHF-Com system?

<p>118.00 - 135.975 MHz</p> Signup and view all the answers

What is the function of the 'com test' control?

<p>To deactivate the receiver squelch circuit</p> Signup and view all the answers

What is the purpose of the receiver squelch circuit?

<p>To quiet receiver background noise</p> Signup and view all the answers

According to Industry Canada regulations, what type of calls or messages have priority over all others?

<p>Distress calls or messages</p> Signup and view all the answers

Study Notes

Aircraft Communication Systems

  • VHF Comm system frequency spectrum: 118.00 – 135.975 MHz

Propagation Considerations

  • VHF Comm: radio waves propagate in a line of sight, limiting range and coverage
  • HF Comm: radio waves can propagate over long distances, using ionosphere and earth's surface to bounce signals

Antenna Configurations

  • VHF Comm: typically uses a quarter-wave vertical antenna on top of the aircraft's fuselage
  • HF Comm: uses various antenna types, including long wire, stinger, integrated, and 'towel bar' antennas, located on top of the fuselage, tail cone, or belly of the aircraft

Simple Block Diagrams

  • VHF Comm system: consists of remote style VHF system, flight deck on/off and volume control, avionics bay, frequency selection, test/squelch, and flight deck VHF comm band
  • HF Comm system: consists of HF components, including on/off and volume control, frequency selection, test/squelch, and HF antenna

HF Comm DO NOTs

  • Do not change channels or transmit during refueling
  • Do not interrupt any communication
  • Do not transmit with a disconnected antenna
  • Do not transmit on TX restricted frequencies (2.5, 5, 10, 15, 20, 25 MHz)
  • Do not ignore TX duty cycle (1 minute on, 4 minutes off)
  • Do not change channels or transmit with personnel near the antenna or ATU

SELCAL (Selective Calling)

  • Purpose: allows flight crew to be alerted by a chime and/or light when there is a radio call intended for that specific aircraft
  • Works with HF and/or VHF radios on an aircraft
  • Aircraft equipped with SELCAL have a 4-letter code, using letters A-S, excluding I, N, and O
  • SELCAL encoder sends 2 groups of 2 tones each as its 'call', each tone corresponding to one of the letters

Antenna Inspection

  • Bonding to aircraft skin: 0.003 ohms
  • Mounting hole and surface sealing: ensure proper sealing to prevent water ingress
  • Leading edge protection: inspect for cracks, erosion, and condition of paint
  • Painting antennas with aircraft paint is not recommended, as it can de-tune the antenna

Regulations

  • Industry Canada regulations: all radio transmitters installed in operating aircraft must be licensed
  • FCC regulations: distress calls or messages have priority over all others

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