FCC Technician Class Exam Study Guide - 2014-2018/Subelement T4 Group A
Station setup: connecting microphones; reducing unwanted emissions; power source; connecting a computer; RF grounding; connecting digital equipment; connecting an SWR meter
The Question PoolEdit
- Which of the following is true concerning the microphone connectors on amateur transceivers?
- A. All transceivers use the same microphone connector type
- B. Some connectors include push-to-talk and voltages for powering the microphone
- C. All transceivers using the same connector type are wired identically
- D. Un-keyed connectors allow any microphone to be connected
For over 100 years of radio 'standards', a number of different connectors and technologies have been used. Some microphones are of the phantom power type in that they require a voltage present to operate optimally. Some microphone connectors even have the key switch built in, but the actual switching is done inside the radio using a higher quality circuit to minimize signal bounce. The correct answer is B.
- How might a computer be used as part of an amateur radio station?
- A. For logging contacts and contact information
- B. For sending and/or receiving CW
- C. For generating and decoding digital signals
- D. All of these choices are correct
Computers, tablets and smartphones are frequently used in amateur radio stations. Free downloadable apps exist to decode digital signals simply by holding the microphone to your radio's speaker. Many encode CW and a few actually decode it (poorly). Finally, of course, you can also look up your contact in an online database to see where you are talking to! The correct answer is D.
- Which is a good reason to use a regulated power supply for communications equipment?
- A. It prevents voltage fluctuations from reaching sensitive circuits
- B. A regulated power supply has FCC approval
- C. A fuse or circuit breaker regulates the power
- D. Power consumption is independent of load
The FCC is unconcerned with power supplies (unless they generate an RF noise). Fuses or Circuit Breakers protect against over-current situations in which a power supply has failed in a way that is has begun drawing too much power. A regulated power supply adjusts the amount of current flow needed to maintain a nominal voltage. That is, if you key your transmitter, your power supply will likely consume ten to 50 times as much current, but should still provide close to the nominal 12 volts expected for proper radio operation. The regulation circuit in working order will never allow a higher voltage to reach the radio. The correct answer is A.
- Where must a filter be installed to reduce harmonic emissions from your station?
- A. Between the transmitter and the antenna
- B. Between the receiver and the transmitter
- C. At the station power supply
- D. At the microphone
When you transmit, the strongest signal is on your fundamental harmonic, but there are other weaker harmonics that must be filtered before they radiate from the antenna. A receiver radiates trivial amounts of RF energy and is of no harm in transmitting from it's antenna. Similar is true for power supplies or microphones. The output of the transmitter must be made compliant before it leaves your shack. The correct answer is A.
- Where should an in-line SWR meter be connected to monitor the standing wave ratio of the station antenna system?
- A. In series with the feed line, between the transmitter and antenna
- B. In series with the station's ground
- C. In parallel with the push-to-talk line and the antenna
- D. In series with the power supply cable, as close as possible to the radio
When attaching equipment that tests the paired performance of your transmitter, the feedline and antenna, it must be attached somewhere between these devices. The correct answer is A
- Which of the following would be connected between a transceiver and computer in a packet radio station?
- A. Transmatch
- B. Mixer
- C. Terminal node controller
- D. Antenna
The good terminal node controller can automatically enable the transmitter to encode and deliver your digital message. A great terminal node controller decodes the reply to a reasonable quality. The correct answer is C.
How is a computer's sound card used when conducting digital communications using a computer?
- A. The sound card communicates between the computer CPU and the video display
- B. The sound card records the audio frequency for video display
- C. The sound card provides audio to the microphone input and converts received audio to digital form
- D. All of these choices are correct
Digital modes are very similar to the computer modems of yesteryear, they transform digital data into an acoustic signal of similar bandwidth as human voice. This allows the data to be transmitted over a channel designed for voice operations. Computer sound cards are ideal tools for generating or capturing digital signals in amateur radio. The correct answer is C.
- Which type of conductor is best to use for RF grounding?
- A. Round stranded wire
- B. Round copper-clad steel wire
- C. Twisted-pair cable
- D. Flat strap
The correct answer is D.
- Which of the following could you use to cure distorted audio caused by RF current flowing on the shield of a microphone cable?
- A. Band-pass filter
- B. Low-pass filter
- C. Preamplifier
- D. Ferrite choke
The correct answer is D.
- What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver's receive audio?
- A. The ignition system
- B. The alternator
- C. The electric fuel pump
- D. Anti-lock braking system controllers
The ignition system does make a certain amount of noise that can be mitigated, but the alternator is considered the most substantial source of the noise. The correct answer is B. Don't even think of selecting fuel pump of brakes, as these should never cause an issue.
- Where should the negative return connection of a mobile transceiver's power cable be connected?
- A. At the battery or engine block ground strap
- B. At the antenna mount
- C. To any metal part of the vehicle
- D. Through the transceiver's mounting bracket
The negative wire, by international standard, is attached to the negative terminal of the battery. As vehicles are increasingly using non-metallic assemblies on vehicles, there is no guarantee that a metal part of the car is attached to electrical ground. The correct answer is A.
- What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter?
- A. Your microphone is picking up noise from an open window
- B. You have the volume on your receiver set too high
- C. You need to adjust your squelch control
- D. Noise on the vehicle's electrical system is being transmitted along with your speech audio
That is the sound of your car's spark ignition system and alternator. If you drive a diesel, well, good for you; this isn't as serious of a problem. You can mitigate such noise by shielding your spark plug wires with metal sheathing and grounding it to your car's frame. (Such sheathing is readily available by cutting open VGA cable on old CRT monitors) The correct answer is D.