What type of antenna pattern is radiated from

• a ground station phased-array directional antenna
  
• when transmitting the PPM pulses
  
• in a Mode S interrogation signal
  
• of an aircraft’s Traffic alert and
  
• Collision Avoidance System (TCAS) installation?

1030 MHz directional pattern.

From n6ju:

"Directional" is in the question, so you know the answer is either A or D because they contain 'directional'.

1030 MHz is for interrogating other TCAS installations.

1090 MHz is for replying to those interrogations.

('Ask' is first - lower number freq;
'Reply' comes after - higher number freq.)

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What type of antenna is used in an aircraft’s Instrument Landing System (ILS) marker beacon installation?

A balanced loop reception antenna.

From n6ju:

In an ILS installation, the aircraft is receiving, not transmitting, so that eliminates the two answers with "radiates" in them.

Of the remaining two choices offered, a loop is more commonly used for direction finding by looking for a null;

ILS just needs to hear the beacon... a folded dipole will work fine for that.

For more information, please see the Aerocorner site for the well-illustrated article on The Different Types of Aircraft Antennas And Their Function

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What is the frequency range of an aircraft’s Very High Frequency (VHF) communications?

118.000 MHz to 136.975 MHz (worldwide up to 151.975 MHz).

From n6ju:

VHF is 30 MHz to 300Mhz, so the two answers with frequencies above 300 Mhz can be eliminated.

Airband starts at 108MHz, which is why some people guess the answer starting with 108Mhz.

However, the low end of the band is for the NAV-aids pilot static test (main page) devices not voice communication. See this page for detailed information, Pitot Static Test Equipment and RVSM Air Data Accessories Kits

Please see the Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 87
Subpart E - Frequencies, especially the paragraph
§ 87.173 Frequencies.

Please see the table of frequencies for allocations, 47 CFR 87.173(b)

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Aircraft Emergency Locator Transmitters (ELT) operate on what frequencies?

121.5, 243 and 406 MHz.

From n6ju:

121.5 is the aircraft emergency frequency.
406 is what both marine EPIRBs and ELTs use for long distance location signaling.

So ELTs use both, 406 for detection by the satellites, and 121.5 for homing by search and rescue teams when they get close enough.

CFR 47 Part 87 subpart E lists both 121.5 Mhz and 406 Mhz as "Emergency and distress", and

243 Mhz as "Emergency and distress" frequency for use of survival craft and emergency locator transmitters.

Please see the Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 87
Subpart E - Frequencies, especially the paragraph
§ 87.173 Frequencies.

Please see the table of frequencies for allocations, 47 CFR 87.173(b)

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What is the frequency range of an aircraft’s radio altimeter?

4250 MHz to 4350 MHz.

From n6ju:

Radio altimeters work by bouncing a signal off the ground below, so VHF and UHF wouldn't be reliable.

Please see the Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 87
Subpart E - Frequencies, especially the paragraph
§ 87.173 Frequencies., as it lists "4200-4400 MHz" as "Radio altimeters" in the table of frequencies.

Please see the table of frequencies for allocations, 47 CFR 87.173(b)

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What type of antenna is attached to an
aircraft’s Mode C transponder installation and used to receive 1030 MHz interrogation signals from the Air Traffic Control Radar Beacon System (ATCRBS)?

An L-band monopole blade-type omnidirectional antenna.

From n6ju:
A transponder has to listen omnidirectionally for the incoming signals it must respond to. So anything directional is inappropriate. That eliminates the phased array (directional), and the rotatable loop.

The frequency of 1030 Mhz is in L-band, and folded dipoles are more common for HF or lower frequencies, where a half-wave dipole length would be large if it were not folded... that is of course not a problem at over 1GHz.

And dipoles are not omnidirectional.

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