Some aircraft and avionics equipment operates with a prime power line frequency of 400 Hz. What is the principle advantage of a higher line frequency?

The magnetic devices in a 400 Hz power supply such as transformers, chokes and filters are smaller and lighter than those used in 60 Hz power supplies.

The 400 Hz power supply uses LESS electrical current that the 60 Hz power supply, leaving more electricity on the airplane for other systems. This is because fewer electric generators are required to produce the 400 Hz current.

Please see Aerospaceweb site for the article 400 Hz Electrical Systems

Also, see FCX Systems site for the article WHY THE AVIATION INDUSTRY OPERATES ON 400 HZ POWER

From the One Monroe Aerospace site in the article Why Airplanes Use 400 Hz Power

"As the frequency of the voltage change was made slower, the size and weight of the transformers and generators increased and became more expensive.

As the frequency was made faster, more power was lost in the transmission lines, which also increased cost.The most economical frequency for the power company was around 60 cycles per second. "

AND

"A special generator was designed to create an output of 400 Hz. This allowed a motor which was the size of a watermelon to be replaced by one the size of a one-pound coffee can which could do the same work.

The saving of weight allowed increased cargo capacity and decreased fuel consumption. Power at 400 Hz for aviation was a success and became the standard of modern AC-powered aircraft."

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Aviation services use predominantly ____ microphones.

Dynamic

Please see My eLearning World for the article What is a Dynamic Microphone and How Does It Work?

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Typical airborne HF transmitters usually provide a nominal RF power output to the antenna of ____ watts, compared with ____ watts RF output from a typical VHF transmitter.

100, 20

Please see the Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 87 AVIATION SERVICES, and search using the word "watts."

Especially, please see the Subpart C - Operating Requirements and Procedures

And, Aviation Nepal site for the well-illustrated article High Frequency (HF), Very High Frequency (VHF), and Transponder usage in Aircraft

Also, please see Wikipedia's article Transmitter Power Output

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Before ground testing an aircraft RADAR, the operator should:

Ensure that the area in front of the antenna is clear of other maintenance personnel to avoid radiation hazards.

The same device powers the radar and microwave oven--magnetron. Radar does not have the door like microwave oven, so standing in front one should never be done.

For more information, please see the CDC Gov site for the pdf document Recommendations for the Report RI 9657, Testing Radar-Based Collision Warning Systems on Heavy Equipment

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What type of antenna is used in an aircraft’s Very High Frequency Omnidirectional Range (VOR) and Localizer (LOC) installations?

Horizontally polarized omnidirection reception antenna.

Same word in question and answer: omnidirectional

Please see Wikipedia's article VHF omnidirectional range

View YouTube video from the MIT Lincoln Laboratory titled Arrays of Horizontally Polarized Omnidirectional Elements | Lecture #13 | Alan Fenn

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What is the function of a commercial aircraft’s SELCAL installation? SELCAL is a type of aircraft communications __________.

System where a ground-based transmitter can call a selected aircraft or group of aircraft without the flight crew monitoring the ground-station frequency.

From wp2ahg:

SELective CALling.

From Wikipedia's article on SELCAL:

"The use of SELCAL allows an aircraft crew to be notified of incoming communications even when the aircraft's radio has been muted. Thus, crewmembers need not devote their attention to continuous radio listening."

Also, please see YouTube video from the Rohde Schwarz channel called Understanding SELCAL

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