Technicians Exam-Station Equipment

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Technicians Exam-Station Equipment
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Amateur Radio Technicians Exam - T7 Question Set - Station Equipment
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  1. T7A01 What is the function of a product detector?
    A. Detect phase modulated signals
    B. Demodulate FM signals
    C. Detect CW and SSB signals
    D. Combine speech and RF signals
    • C. Detect CW and SSB signals
    • Detectors for CW and SSB need to reproduce the signal’s frequencies, not just their amplitude. To recover these signals, a product detector detects CW and SSB signals by combining a signal at the frequency of the modulated signal’s RF carrier with the modulated signal itself. The product detector works very much like a mixer except that one of its output products is the original modulating signal, thus the name product detector. [Ham Radio License Manual, page 3-17]
  2. T7A02 What type of receiver is shown in Figure T6?

    A. Direct conversion
    B. Super-regenerative
    C. Single-conversion superheterodyne
    D. Dual-conversion superheterodyne
    • C. Single-conversion superheterodyne
    • The superheterodyne receiver shown in the figure is the standard in Amateur Radio today. The key characteristic of the “superhet” is the use of mixers to shift incoming signals of any frequency to a single fixed frequency, called the intermediate frequency (IF). Unwanted signals can then rejected by narrow filters. An IF amplifier then amplifies the signal so that it can be demodulated and the information recovered. The IF may be either the sum or difference of the frequencies of the oscillator and the modulated RF signal. After amplification and filtering at the IF, the signal is then demodulated. In the figure, a product detector follows the IF amplifier, recovering a CW or SSB signal (see question T7A01). In a superhet, the oscillator used by the product detector is called a beat frequency oscillator (BFO) because it can be adjusted to produce different tones or frequencies, called “beats” originally, in the output signal. Because this receiver has only one mixer and IF it is a single-conversion superheterodyne. [Ham Radio License Manual, page 3-18] *T7A01 - Detectors for CW and SSB need to reproduce the signal’s frequencies, not just their amplitude. To recover these signals, a product detector detects CW and SSB signals by combining a signal at the frequency of the modulated signal’s RF carrier with the modulated signal itself. The product detector works very much like a mixer except that one of its output products is the original modulating signal, thus the name product detector. [Ham Radio License Manual, page 3-18]
  3. T7A03 What is the function of a mixer in a superheterodyne receiver?
    A. To reject signals outside of the desired passband
    B. To combine signals from several stations together
    C. To shift the incoming signal to an intermediate frequency
    D. To connect the receiver with an auxiliary device, such as a TNC
    • C. To shift the incoming signal to an intermediate frequency
    • The superheterodyne receiver shown in the figure is the standard in Amateur Radio today. The key characteristic of the “superhet” is the use of mixers to shift incoming signals of any frequency to a single fixed frequency, called the intermediate frequency (IF). Unwanted signals can then rejected by narrow filters. An IF amplifier then amplifies the signal so that it can be demodulated and the information recovered. The IF may be either the sum or difference of the frequencies of the oscillator and the modulated RF signal. After amplification and filtering at the IF, the signal is then demodulated. In the figure, a product detector follows the IF amplifier, recovering a CW or SSB signal (see question T7A01). In a superhet, the oscillator used by the product detector is called a beat frequency oscillator (BFO) because it can be adjusted to produce different tones or frequencies, called “beats” originally, in the output signal. Because this receiver has only one mixer and IF it is a single-conversion superheterodyne. [Ham Radio License Manual, page 3-18] *T7A01 - Detectors for CW and SSB need to reproduce the signal’s frequencies, not just their amplitude. To recover these signals, a product detector detects CW and SSB signals by combining a signal at the frequency of the modulated signal’s RF carrier with the modulated signal itself. The product detector works very much like a mixer except that one of its output products is the original modulating signal, thus the name product detector. [Ham Radio License Manual, page 3-18]
  4. T7A04 What circuit is pictured in Figure T7, if block 1 is a frequency discriminator?

    A. A double-conversion receiver
    B. A regenerative receiver
    C. A superheterodyne receiver
    D. An FM receiver
    • D. An FM receiver (Block 1 is a discriminator)
    • Figure T7-2 (exam diagram T7) shows how a superheterodyne receiver is built to receive an FM voice signal. The input signal passes through the mixer-oscillator-IF amplifier sequence across the top of the diagram. Instead of immediately demodulating the FM signal, however, it is applied to a limiter. A limiter is a high-gain amplifier that removes all amplitude variations from the signal, leaving only the frequency variations that represent the modulation of the signal. The output of the limiter can then be applied to a discriminator to recover the voice signal that is then amplified and heard on a speaker. [Ham Radio License Manual, page 3-19]
  5. T7A05 What is the function of block 1 if figure T4 is a simple CW transmitter?
    A. Reactance modulator
    B. Product detector
    C. Low-pass filter
    D. Oscillator
    • D. Oscillator
    • Figure T7-3 (exam diagram T4) shows the block diagram of a basic CW transmitter. The oscillator at left produces a low-power signal at one frequency. Oscillators are used in both receivers and transmitters to determine the operating frequency. In a transmitter, the output signal from an oscillator is modulated and amplified before actually being applied to an antenna. The output signal from the oscillator is not strong enough for reliable communication over long distances. The next stage of the transmitter, reading left to right, is an amplifier circuit called a driver that makes the signal stronger. The driver stage allows the oscillator to operate continuously at low power so that its frequency remains stable. The output of the driver is then applied to a power amplifier whose output is strong enough to provide a useful signal for communication with other stations. In order to turn the output signal on and off as Morse code, the driver and power amplifier stages are keyed (switched on and off) by a telegraph key. The oscillator can then run continuously and that also helps keep its signal frequency stable. [Ham Radio License Manual, page 3-15]
  6. T7A06 What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal?
    A. High-pass filter
    B. Low-pass filter
    C. Transverter
    D. Phase converter
    • C. Transverter
    • The superheterodyne technique of shifting signal frequencies can also be applied at the equipment level to convert an entire transceiver to operate on a band other than it was designed for. Instead of a mixer, a piece of equipment called a transverter is used. Low-power transmitter output signals on one band are shifted to the new output frequency where they are amplified for transmission. A receiving converter (basically a mixer) shifts incoming signals to the desired band where they are received as regular signals by the transceiver. Transverters are used by many hams to allow one main transceiver to be used on one or more new bands. For example, with few transceivers available for CW and SSB operation on 222 MHz, a transverter is used to convert 222 MHz signals to and from the 28 MHz band available on all HF gear. [Ham Radio License Manual, page 3-19]
  7. T7A07 If figure T5 represents a transceiver in which block 1 is the transmitter portion and block 3 is the receiver portion, what is the function of block 2?
    A. A balanced modulator
    B. A transmit-receive switch
    C. A power amplifier
    D. A high-pass filter
    • B. A transmit-receive switch
    • The three basic elements of a ham radio station, big or small, are the transmitter, receiver, and antenna as shown in Figure T7-4 (exam diagram T5). A transmitter (abbreviated XMTR) generates a signal that carries speech, Morse code or data information. A receiver (abbreviated RCVR) recovers the speech, Morse code or data information from a signal. An antenna turns the radio signals from a transmitter into energy that travels through space as a radio wave. An antenna also captures radio waves and turns them into signals for a receiver to work with. A feed line connects the antenna to the transmitter or receiver. Feed lines are also called transmission lines, just like power lines, because they are used to transfer energy — radio signals in this case. Most amateur equipment combines the transmitter and receiver into a single piece of equipment called a transceiver (abbreviated XCVR). This is what hams mean when they refer to something as a radio. A transceiver shares a single antenna between the transmitter and receiver circuits by using a transmit-receive (TR) switch. [Ham Radio License Manual, page 2-11]
  8. T7A08 Which of the following circuits combines a speech signal and an RF carrier?
    A. Beat frequency oscillator
    B. Discriminator
    C. Modulator
    D. Noise blanker
    • C. Modulator
    • The process of combining data or voice signals with an RF signal is modulation. A circuit that performs the modulation function is therefore called a modulator. The function of the modulator is to add the data or voice signal to an RF signal or carrier. The result is an RF signal that can be communicated by radio. A modulator can be as simple as an on-off switch (a telegraph key, for example) or it can be very complex in the case of a high-speed data transmission. [Ham Radio License Manual, page 3-16]
  9. T7A09 Which of the following devices is most useful for VHF weak-signal communication?
    A. A quarter-wave vertical antenna
    B. A multi-mode VHF transceiver
    C. An omni-directional antenna
    D. A mobile VHF FM transceiver
    • B. A multi-mode VHF transceiver
    • Most VHF “weak-signal” contacts are made using SSB or CW because those modes give better performance over long distances. This style of operating also uses horizontally-polarized directional antennas (beams). Since FM is not used, you’ll need a multi-mode transceiver to use SSB or CW for VHF/UHF DXing. [Ham Radio License Manual, page 6-30]
  10. T7A10 What device increases the low-power output from a handheld transceiver?
    A. A voltage divider
    B. A RF power amplifier
    C. An impedance network
    D. A voltage regulator
    • B. A RF power amplifier
    • Amplifiers are used to increase the strength of audio or radio signals. Amplifiers used to increase the power of transmitted RF signals are called power amplifiers or linear amplifiers. Amplifiers used to increase the strength of a received signal are called preamplifiers or just preamps. [Ham Radio License Manual, page 5-7]
  11. T7A11 Which of the following circuits demodulates FM signals?
    A. Limiter
    B. Discriminator

    C. Product detector
    D. Phase inverter
    • B. Discriminator
    • Figure T7-2 (exam diagram T7) shows how a superheterodyne receiver is built to receive an FM voice signal. The input signal passes through the mixer-oscillator-IF amplifier sequence across the top of the diagram. Instead of immediately demodulating the FM signal, however, it is applied to a limiter. A limiter is a high-gain amplifier that removes all amplitude variations from the signal, leaving only the frequency variations that represent the modulation of the signal. The output of the limiter can then be applied to a discriminator to recover the voice signal that is then amplified and heard on a speaker. [Ham Radio License Manual, page 3-19]
  12. T7A12 Which term describes the ability of a receiver to discriminate between multiple signals?
    A. Tuning rate
    B. Sensitivity
    C. Selectivity
    D. Noise floor
    • C. Selectivity
    • Receivers are compared on the basis of two primary characteristics; sensitivity and selectivity. A receiver’s sensitivity determines its ability to detect weak signals. Higher sensitivity means a receiver can detect weaker signals. Sensitivity is specified as a minimum detectable signal level, usually in microvolts. Selectivity is the ability of a receiver to retrieve the information from just the desired signal in the presence of unwanted signals. High selectivity means that a receiver can operate properly even in the presence of strong signals on nearby frequencies. Receivers use filters to reject the unwanted signals. [Ham Radio License Manual, page 3-19]
  13. T7A12 Where is an RF preamplifier installed?
    A. Between the antenna and receiver
    B. At the output of the transmitter’s power amplifier
    C. Between a transmitter and antenna tuner
    D. At the receiver’s audio output
    • A. Between the antenna and receiver
    • If a receiver is not sensitive enough (see question T7A12), a preamplifier or preamp can be connected between the antenna and receiver. [Ham Radio License Manual, page 3-19] *T7A12 - Receivers are compared on the basis of two primary characteristics; sensitivity and selectivity. A receiver’s sensitivity determines its ability to detect weak signals. Higher sensitivity means a receiver can detect weaker signals. Sensitivity is specified as a minimum detectable signal level, usually in microvolts. Selectivity is the ability of a receiver to retrieve the information from just the desired signal in the presence of unwanted signals. High selectivity means that a receiver can operate properly even in the presence of strong signals on nearby frequencies. Receivers use filters to reject the unwanted signals. [Ham Radio License Manual, page 3-19]
  14. T7B01 What can you do if you are told your FM handheld or mobile transceiver is over deviating?
    A. Talk louder into the microphone
    B. Let the transceiver cool off
    C. Change to a higher power level
    D. Talk farther away from the microphone
    • D. Talk farther away from the microphone
    • Excessive modulation for all types of speech results in distortion of transmitted speech and unwanted or spurious transmitter outputs on adjacent frequencies where they cause interference. Those unwanted transmitter outputs have lots of names, but the most common is splatter. Generating those outputs is called splattering, as in, “You’re splattering 10 kHz away!” An overmodulated FM signal has excessive deviation and is said to be over-deviating. Over-deviation is usually caused by speaking too loudly into the microphone and may cause interference on adjacent channels. An FM transmitter can also be internally misadjusted to over-deviate at normal speech levels. To reduce over-deviation, speak more softly or move the microphone farther from your mouth. [Ham Radio License Manual, page 5-4]
  15. T7B02 What is meant by fundamental overload in reference to a receiver?
    A. Too much voltage from the power supply
    B. Too much current from the power supply
    C. Interference caused by very strong signals
    D. Interference caused by turning the volume up too high
    • C. Interference caused by very strong signals
    • Very strong signals may overwhelm a receiver’s ability to reject them. Receiver overload is a common type of interference to TV and FM-broadcast receivers. It happens most often to consumer electronic equipment near an amateur station or other transmitter. Symptoms of overload include severe interference on all channels of a TV or FM receiver or an amateur may hear noise across an entire band when the strong signal is present. If adding attenuation (either by turning on a receiver’s attenuator or removing an antenna) causes the interference to disappear, it’s probably caused by overload. When the RF signal (at the fundamental frequency) enters the receiver, it overloads one or more circuits. The receiver front end (first circuit stages after the antenna) is most commonly affected. [Ham Radio License Manual, page 5-20]
  16. T7B03 Which of the following may be a cause of radio frequency interference?
    A. Fundamental overload
    B. Harmonics
    C. Spurious emissions
    D. All of these choices are correct
    • D. All of these choices are correct
    • All three of the choices cause interference by disrupting receiver performance (A) or by creating unwanted signals that directly interfere with desired signals (B and C). As more and more electronic devices and electrical appliances are put in use every day, interference between them and radios, called radio frequency interference (RFI), becomes more commonplace. RFI can occur in either “direction” — to or from the Amateur Radio equipment. Interference becomes more severe with higher power or closer spacing to the signal source. The ARRL’s Technical Information Service Web page provides information on all kinds of RFI and the means to correct it. [Ham Radio License Manual, page 5-18]
  17. T7B04 What is the most likely cause of interference to a non-cordless telephone from a nearby transmitter?
    A. Harmonics from the transmitter
    B. The telephone is inadvertently acting as a radio receiver
    C. Poor station grounding
    D. Improper transmitter adjustment
    • B. The telephone is inadvertently acting as a radio receiver
    • The major cause of telephone interference comes from telephones that were not equipped with interference protection when they were manufactured. (Reference: FCC CIB Telephone Interference Bulletin) Radio frequency energy from your amateur transmitter may be strong enough to cause the telephone to act as a receiver through direct detection, the most common form of interference to telephones. As with receiver overload, there is nothing you can do at the transmitter to cure the interference. Interference protection measures must be taken at, or in, the telephone in question. [Ham Radio License Manual, page 5-20]
  18. T7B05 What is a logical first step when attempting to cure a radio frequency interference problem in a nearby telephone?
    A. Install a low-pass filter at the transmitter
    B. Install a high-pass filter at the transmitter
    C. Install an RF filter at the telephone
    D. Improve station grounding
    • C. Install an RF filter at the telephone
    • If a telephone is responding to a strong nearby RF signal, the first step should be to prevent the RF from getting into the telephone in the first place. Since RF is probably entering the telephone through the wiring that connects it to the telephone network, an RF filter should be used. Low-pass filters connected at the telephone’s modular jack are the best way to reduce RFI from direct detection. These filters are available at electronics stores. Cordless phones may also suffer from fundamental overload as described in question T7B04. [Ham Radio License Manual, page 5-20] *T7B04 - The major cause of telephone interference comes from telephones that were not equipped with interference protection when they were manufactured. (Reference: FCC CIB Telephone Interference Bulletin) Radio frequency energy from your amateur transmitter may be strong enough to cause the telephone to act as a receiver through direct detection, the most common form of interference to telephones. As with receiver overload, there is nothing you can do at the transmitter to cure the interference. Interference protection measures must be taken at, or in, the telephone in question. [Ham Radio License Manual, page 5-20]
  19. T7B06 What should you do first if someone tells you that your station’s transmissions are interfering with their radio or TV reception?
    A. Make sure that your station is functioning properly and that it does not cause interference to your own television
    B. Immediately turn off your transmitter and contact the nearest FCC office for assistance
    C. Tell them that your license gives you the right to transmit and nothing can be done to reduce the interference
    D. Continue operating normally because your equipment cannot possibly cause any interference
    • A. Make sure that your station is functioning properly and that it does not cause interference to your own television
    • You should first make sure that your equipment is operating properly and not creating spurious signals on the TV channels. Check for interference to your own TV. If you see it, stop operating and cure the problem before you go back on the air. [Ham Radio License Manual, page 5-21]
  20. T7B07 Which of the following may be useful in correcting a radio frequency interference problem?
    A. Snap-on ferrite chokes
    B. Low-pass and high-pass filters
    C. Band-reject and band-pass filters
    D. All of these choices are correct
    • D. All of these choices are correct
    • Knowing how to use the different kinds of filters and RF blocking materials such as ferrite cores is an important part of the amateur’s repertoire. If you are having an interference problem, members of your club may be able to help you. The ARRL also maintains an RF Interference resource Web page as part of the Technical Information Service area on the ARRL Web site. [Ham Radio License Manual, page 5-18]
  21. T7B08 What should you do if a “Part 15” device in your neighbor’s home is causing harmful interference to your amateur station?
    A. Work with your neighbor to identify the offending device
    B. Politely inform your neighbor about the rules that require him to stop using the device if it causes interference
    C. Check your station and make sure it meets the standards of good amateur practice
    D. All of these choices are correct
    • D. All of these choices are correct
    • Part 15 refers to the section of the FCC Rules that permits unlicensed devices to use radio frequencies as part of their function. This includes cordless phones, baby monitors, audio and video relay devices, and wireless computer data links. These devices are allowed to use the radio spectrum, but are not permitted to cause interference to stations in licensed services, such as Amateur Radio. This is one of the benefits of being a licensed station — protection against interference. Users of Part 15 devices are required to accept interference to the devices from stations in a licensed service, such as Amateur Radio or a broadcast station. These rules must be printed either directly on the device or in the owner’s manual supplied with the device. While this means that the responsibility for stopping the interference may lie with your neighbor, you should still make sure the interference is not occurring because of some problem in your station. If you are sure your station is operating properly, you may need to politely educate your neighbor about the interference and help identify the offending device. [Ham Radio License Manual, page 5-22]
  22. T7B09 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
    • D. Noise on the vehicle’s electrical system is being transmitted along with your speech audio
    • Vehicle power wiring often carries a significant amount of noise that can affect your radio’s operation. Alternator whine is caused by noise on the dc power system inside your own vehicle. You might hear it with the received audio but more likely it will be heard by others as a high-pitched whine on your transmitted audio that varies with your engine speed. It can be removed by a dc power filter at your radio. [Ham Radio License Manual, page 5-15]
  23. T7B10 What might be the problem if you receive a report that your audio signal through the repeater is distorted or unintelligible?
    A. Your transmitter may be slightly off frequency
    B. Your batteries may be running low
    C. You could be in a bad location
    D. All of these choices are correct
    • D. All of these choices are correct
    • A station that is slightly off-frequency will be strong, but distorted. This sometimes happens when a radio control key gets bumped, changing frequency by a small amount. If accidentally pressing a control key on your radio is a frequent problem (smaller radios are particularly prone to it), try using the LOCK feature of your radio to disable unintended key presses. You could also be causing excessive deviation by speaking too loudly into the microphone. Either lower your voice or hold the microphone farther away from your mouth. Weak or low batteries can also cause distorted audio by causing the transmitter’s modulator circuitry to function improperly. [Ham Radio License Manual, page 6-12]
  24. T7B11 What is a symptom of RF feedback in a transmitter or transceiver?
    A. Excessive SWR at the antenna connection
    B. The transmitter will not stay on the desired frequency
    C. Reports of garbled, distorted, or unintelligible transmissions
    D. Frequent blowing of power supply fuses
    • C. Reports of garbled, distorted, or unintelligible transmissions
    • It is not unusual for RF current flowing in sensitive audio cables or data cables to interfere with your station’s normal function, just as your strong transmitter signal might be picked up and detected by a neighbor’s telephone or audio system. “RF feedback” via a microphone cable can cause distorted transmitted audio, for example. [Ham Radio License Manual, page 5-23]
  25. T7B12 What does the acronym “BER” mean when applied to digital communications systems?
    A. Baud Enhancement Recovery
    B. Baud Error Removal
    C. Bit Error Rate
    D. Bit Exponent Resource
    • C. Bit Error Rate
    • A radio signal experiences many disruptions between the transmitter and receiver; fading, interference, noise often introduce errors into the stream of data, measured by the bit error rate (BER). These would cause errors in the received information if no precautions were taken. Some codes include extra data elements to allow the receiver to detect an error. For example, a parity bit can be used to detect simple errors in a single character of data. Some protocols add special data so that common errors can be detected and sometimes even corrected. [Ham Radio License Manual, page 5-8]
  26. T7C01 What is the primary purpose of a dummy load?
    A. To prevent the radiation of signals when making tests
    B. To prevent over-modulation of your transmitter
    C. To improve the radiation from your antenna
    D. To improve the signal to noise ratio of your receiver
    • A. To prevent the radiation of signals when making tests
    • To avoid interfering with other stations while you’re adjusting your transmitter or measuring its output power, it’s a good idea to use a dummy load. A dummy load is a heavy-duty resistor that can absorb and dissipate the output power from a transmitter. Because the dummy load absorbs all of the transmitter output and radiates it as heat instead of radio waves, there is no signal to interfere with other hams. You should always use a dummy load when testing a transmitter unless you absolutely have to make an on-the-air test. [Ham Radio License Manual, page 5-4]
  27. T7C02 Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?
    A. A VTVM
    B. An antenna analyzer
    C. A “Q” meter
    D. A frequency counter
    • B. An antenna analyzer
    • An antenna analyzer consists of a very low-power signal source with an adjustable frequency and one or more meters or displays to show the impedance and SWR. It is used to measure an antenna system without using a transmitter whose signal might cause interference. [Ham Radio License Manual, page 4-18]
  28. T7C03 What, in general terms, is standing wave ratio (SWR)?
    A. A measure of how well a load is matched to a transmission line
    B. The ratio of high to low impedance in a feedline
    C. The transmitter efficiency ratio
    D. An indication of the quality of your station’s ground connection
    • A. A measure of how well a load is matched to a transmission line
    • Standing wave ratio, or SWR, is caused by a mismatch of the characteristic impedance of the feed line and that of a load (such as an antenna) attached to the feed line. Some of the energy delivered by the feed line is reflected at the load and interferes with the incoming energy, creating stationary patterns called standing waves. The magnitude of the SWR is the ratio of the maximum and minimum values of the standing wave pattern. SWR is also the ratio of the higher of the two impedances to the lower. [Ham Radio License Manual, page 4-10]
  29. T7C04 What reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline?
    A. 2 to 1
    B. 1 to 3
    C. 1 to 1
    D. 10 to 1
    • C. 1 to 1
    • When there is no reflected power there is no interference pattern and the SWR is 1:1. This condition is called a perfect match. [Ham Radio License Manual, page 4-10]
  30. T7C05 What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?
    A. 2 to 1
    B. 1 to 2
    C. 6 to 1
    D. 10 to 1
    • A. 2 to 1
    • One possible effect of high SWR is that the interference pattern causes voltages to increase in the feed line and at the transmitter’s output where the feed line is connected. The higher voltages can damage a transmitter’s output circuits. Most amateur transmitting equipment is designed to work at full power with an SWR of 2:1 or lower. SWR greater than 2:1 may cause the transmitter to reduce power automatically in order to protect its output circuit. [Ham Radio License Manual, page 4-10]
  31. T7C06 What does an SWR reading of 4:1 mean?
    A. An antenna loss of 4 dB
    B. A good impedance match
    C. An antenna gain of 4
    D. An impedance mismatch
    • D. An impedance mismatch
    • SWR greater than 1:1 is called an impedance mismatch or mismatch. [Ham Radio License Manual, page 4-10]
  32. T7C07 What happens to power lost in a feedline?
    A. It increases the SWR
    B. It comes back into your transmitter and could cause damage
    C. It is converted into heat
    D. It can cause distortion of your signal
    • C. It is converted into heat
    • As energy travels through a feed line, some of it is absorbed by the insulation in the line and some is lost in the resistance of the conductors themselves. These losses are in the form of heat, just as if the energy was dissipated by a resistor. Feed lines used at radio frequencies use special materials and construction methods to minimize power being dissipated as heat by feed line loss and to avoid signals leaking in or out. [Ham Radio License Manual, page 4-8]
  33. T7C08 What instrument other than an SWR meter could you use to determine if a feedline and antenna are properly matched?
    A. Voltmeter
    B. Ohmmeter
    C. Iambic pentameter
    D. Directional wattmeter
    • D. Directional wattmeter
    • A directional wattmeter can tell you how much energy is flowing in each direction along a feed line. From the relative amounts of power flowing in each direction, you can calculate SWR. By minimizing reflected power, you can adjust your antenna for the best impedance match. [Ham Radio License Manual, page 4-17]
  34. T7C09 Which of the following is the most common cause for failure of coaxial cables?
    A. Moisture contamination
    B. Gamma rays
    C. The velocity factor exceeds 1.0
    D. Overloading
    • A. Moisture contamination
    • Coaxial cables must be protected. The performance of coaxial cable depends on the integrity of its outer coating, the jacket. Nicks, cuts and scrapes can all breach the jacket allowing moisture contamination, the most common cause of coaxial cable failure. Prolonged exposure to the ultraviolet (UV) in sunlight will also cause the plastic in the jacket to degrade, causing small cracks that allow water into the cable. To protect the cable against UV damage the jacket usually contains a pigment that absorbs and blocks the UV. Capillary action of the strands making up the braided outer shield can also draw water into coaxial cable. Once in the cable, the water causes both corrosion and heat losses in the shield. Water can also get into coaxial cable through an improperly sealed connection. [Ham Radio License Manual, page 4-16]
  35. T7C10 Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
    A. Ultraviolet resistant jackets prevent harmonic radiation
    B. Ultraviolet light can increase losses in the cable’s jacket
    C. Ultraviolet and RF signals can mix together, causing interference
    D. Ultraviolet light can damage the jacket and allow water to enter the cable
    • D. Ultraviolet light can damage the jacket and allow water to enter the cable
    • Coaxial cables must be protected. The performance of coaxial cable depends on the integrity of its outer coating, the jacket. Nicks, cuts and scrapes can all breach the jacket allowing moisture contamination, the most common cause of coaxial cable failure. Prolonged exposure to the ultraviolet (UV) in sunlight will also cause the plastic in the jacket to degrade, causing small cracks that allow water into the cable. To protect the cable against UV damage the jacket usually contains a pigment that absorbs and blocks the UV. Capillary action of the strands making up the braided outer shield can also draw water into coaxial cable. Once in the cable, the water causes both corrosion and heat losses in the shield. Water can also get into coaxial cable through an improperly sealed connection. [Ham Radio License Manual, page 4-16]
  36. T7C11 What is a disadvantage of “air core” coaxial cable when compared to foam or solid dielectric types?
    A. It has more loss per foot
    B. It cannot be used for VHF or UHF antennas
    C. It requires special techniques to prevent water absorption
    D. It cannot be used at below freezing temperatures
    • C. It requires special techniques to prevent water absorption
    • Coax connectors exposed to the weather must be carefully waterproofed. If you use low-loss air-core coax, you will need to pay extra attention to waterproofing the connectors because special techniques are required to prevent water absorption by this cable. [Ham Radio License Manual, page 4-17]
  37. T7D01 Which instrument would you use to measure electric potential or electromotive force?
    A. An ammeter
    B. A voltmeter
    C. A wavemeter
    D. An ohmmeter
    • B. A voltmeter
    • Electromagnetic force (EMF) is another term for voltage, which is measured in volts. A meter used to measure voltage is called a voltmeter. [Ham Radio License Manual, page 3-1]
  38. T7D02 What is the correct way to connect a voltmeter to a circuit?
    A. In series with the circuit
    B. In parallel with the circuit
    C. In quadrature with the circuit
    D. In phase with the circuit
    • B. In parallel with the circuit
    • Voltmeters are connected in parallel with a component (also termed “across a component”) or circuit to measure voltage. Voltage is always measured from one point to another or with respect to some reference voltage. [Ham Radio License Manual, page 3-3]
  39. T7D03 How is an ammeter usually connected to a circuit?
    A. In series with the circuit
    B. In parallel with the circuit
    C. In quadrature with the circuit
    D. In phase with the circuit
    • A. In series with the circuit
    • Ammeters are connected in series with a component or circuit to measure current. Some meters calibrated in amperes are really voltmeters that measure the voltage across a small resistor in series with the current. Be sure to determine which type of meter you have before using it. [Ham Radio License Manual, page 3-3]
  40. T7D04 Which instrument is used to measure electric current?
    A. An ohmmeter
    B. A wavemeter
    C. A voltmeter
    D. An ammeter
    • D. An ammeter
    • The units of current flow are amperes and a meter used to measure current is called an ammeter. [Ham Radio License Manual, page 3-1]
  41. T7D05 What instrument is used to measure resistance?
    A. An oscilloscope
    B. A spectrum analyzer
    C. A noise bridge
    D. An ohmmeter
    • D. An ohmmeter
    • The units of resistance are ohms and a meter used to measure resistance is called an ohmmeter. [Ham Radio License Manual, page 3-4]
  42. T7D06 Which of the following might damage a multimeter?
    A. Measuring a voltage too small for the chosen scale
    B. Leaving the meter in the milliamps position overnight
    C. Attempting to measure voltage when using the resistance setting
    D. Not allowing it to warm up properly
    • C. Attempting to measure voltage when using the resistance setting
    • The flexibility afforded by a multimeter also means that it is important to use the meter properly. Trying to measure voltage or connecting the probes to an energized circuit when the meter is set to measure resistance is a common way to damage a multimeter, for example. [Ham Radio License Manual, page 3-3]
  43. T7D07 Which of the following measurements are commonly made using a multimeter?
    A. SWR and RF power
    B. Signal strength and noise
    C. Impedance and reactance
    D. Voltage and resistance
    • D. Voltage and resistance
    • The typical multimeter uses a switch and different sets of input connections to select which parameter and range of values to measure. The most common measurements are voltage, resistance, and current. The convenience of having all the different functions in a single instrument more than outweighs the extra complexity of learning to use a multimeter. [Ham Radio License Manual, page 3-3]
  44. T7D08 Which of the following types of solder is best for radio and electronic use?
    A. Acid-core solder
    B. Silver solder
    C. Rosin-core solder
    D. Aluminum solder
    • C. Rosin-core solder
    • Learning how to install your own coax connectors and make cables not only saves money but allows you to make repairs at home and under emergency conditions! Start by reading the ARRL Technical Information Service’s online article “The Art of Soldering.” Follow up with “Connectors For All Occasions, Parts 1 and 2” on the same Web page. You’ll learn what kind of solder to use for electronics (rosin-core), what a “cold” solder joint looks like (it has a grainy or dull surface), and many other useful tips. [Ham Radio License Manual, page 4-17]
  45. T7D09 What is the characteristic appearance of a “cold” solder joint?
    A. Dark black spots
    B. A bright or shiny surface
    C. A grainy or dull surface
    D. A greenish tint
    • C. A grainy or dull surface
    • Learning how to install your own coax connectors and make cables not only saves money but allows you to make repairs at home and under emergency conditions! Start by reading the ARRL Technical Information Service’s online article “The Art of Soldering.” Follow up with “Connectors For All Occasions, Parts 1 and 2” on the same Web page. You’ll learn what kind of solder to use for electronics (rosin-core), what a “cold” solder joint looks like (it has a grainy or dull surface), and many other useful tips. [Ham Radio License Manual, page 4-17]
  46. T7D10 What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time?
    A. The ohmmeter is defective
    B. The circuit contains a large capacitor
    C. The circuit contains a large inductor
    D. The circuit is a relaxation oscillator
    • B. The circuit contains a large capacitor
    • This is an indication that a large (high-value) capacitor is part of the circuit. As the meter transfers energy to the capacitor it begins to appear more like a high-value resistor to the multimeter’s dc resistance measuring circuit. You’ll find out more about capacitor charging when you begin studying for your General class license. [Ham Radio License Manual, page 3-3]
  47. T7D11 Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter?
    A. Ensure that the applied voltages are correct
    B. Ensure that the circuit is not powered
    C. Ensure that the circuit is grounded
    D. Ensure that the circuit is operating at the correct frequency
    • B. Ensure that the circuit is not powered
    • A circuit with power applied can cause enough current to flow in a multimeter’s sensitive resistance measurement circuits to cause measurement errors or even damage the meter. Always make sure power is removed from a circuit before making resistance measurements. [Ham Radio License Manual, page 3-3]

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