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352 Cards in this Set

  • Front
  • Back
What AFMAN lists the duties of an Airfield Systems Technician?
AFMAN 36–2108, Airman Classification Manual.
As Airfield Systems technicians, do we maintain Air Traffic Control Radar equipment?
NO!
List the duties of an Airfield Systems technician?
An Airfield Systems Technician installs, maintains, and modifies fixed and mobile meteorological and navigational aids systems, ground-to-air transmitters, receivers and transceivers. Maintains non-radar air traffic control and airfield operations communications equipment. Accomplishes flight inspection duties. Analyzes equipment performance trends.
What are the main reasons people are killed each year from electric shock?
Complacency, carelessness, and laziness.
What usually causes death or injury from electric shock?
Heart muscle spasm (ventricular fibrillation) or paralysis of the breathing center.
What factors determine the seriousness of an electric shock?
Voltage, electrical resistance of the body, the duration of the current, the exact path the current takes, and the condition of the body organs.
How quickly must the heart of a shock victim be resuscitated to prevent death?
Within four to six minutes.
What amount of current is sufficient to prevent voluntary control of muscles?
About 10 mA.
What is a poisonous substance that causes flesh to be eaten away?
A caustic or corrosive substance.
What is the easiest way to determine if a substance is toxic?
Read the product label.
What is a material safety data sheet (MSDS)?
A sheet produced by the manufacturer that provides detailed safety information concerning the product.
What is the main hazard associated with general purpose detergent?
It’s an eye irritant.
When soldering, what must you do to avoid ingesting fluxes?
After handling fluxes, wash your hands thoroughly.
What is the main hazard posed by paints and thinners?
Vapor concentrations causing skin and respiratory irritation, light-headedness, giddiness, and nausea. Repeated and prolonged overexposure can cause brain and nervous system damage and may be fatal.
What is produced when your body absorbs radio frequency (RF) power?
Heat.
Harmful effects of overexposure to RF radiation are generally attributed to what factors?
An increase in body temperature or a temperature rise in sensitive organs such as the reproductive system and the eyes.
Where can you get data on the permissible exposure limits of your equipment?
The local Bioenvironmental Health Office and your work center.
What two categories of human factors cause hazards?
Mental and physical.
List some examples of mental human factors.
Attitude, emotion, job pressures, domestic pressures, distractions, job knowledge, and hurrying.
List some examples of physical human factors.
Fatigue, physical strength, reactions to prescription medications or drugs.
Being distracted from a task by personal problems is an example of which type of human factor hazard?
Mental.
Being drowsy on the job is an example of which type of human factor hazard?
Physical.
What are three weather-related climbing hazards?
Ice, rain, and wind.
Why does bulky clothing present a climbing hazard?
Bulky clothing can easily get snagged on any protruding object and cause you to lose your balance.
Why does climbing a tower or working around an antenna provide unique electrical safety hazard?
When you’re working on an antenna or tower, chances are you’re in contact with that tower, providing an excellent path to ground for any electrical potential with which you come in contact.
When working aloft in the vicinity of overhead power lines, what precautions must you take?
Never work alone, and always work under the supervision of experienced persons in accordance with the applicable AFOSH standards.
What is the mission of a fixed base?
To provide communications, navigation, and weather data to ensure personnel and aircraft can safely use the airfield.
What types of equipment are usually at a fixed base?
Fixed navigation systems, weather systems, and a permanent control tower.
What must always be in the forefront of your mind?
Readiness to deploy and support the AEF needs. Safety Always...
What is the mission of the deployed base?
To provide communications, navigation, and weather data to ensure personnel and aircraft can safely use the airfield.
What determines the configuration of the deployed base?
The mission of the base.
With what letters do most equipment designators start at a deployed base?
T or M, for example TRN–26, TRN–41, TRN–45, MSN–7.
What is the key to airpower?
Flexibility.
What AFMAN lists the specific duties of the Airfield Systems technician?
36–2108, Airman Classification manual outlines your specific duties as an Airfield Systems Technician.
How much electric current is of sufficient intensity to prevent voluntary control of muscles?
10 mA.
What is the minimum amount of electric current needed to be fatal?
100 mA.

A current of about 1 mA of shock can be felt, at about 10 mA, the shock is sufficient intensity to prevent voluntary control of the muscles, and at about 100 mA, the shock is fatal.
What poisonous substances can eat away flesh on contact?
Corrosives.
General-purpose detergents (spray and wipe) used in most work centers are
eye irritants.
In addition to the eyes, what organs of the body is/are susceptible to overexposure to radio frequency (RF) radiation?
Reproductive organs.
The two categories of hazards that are considered human factors are
mental and physical.
Being distracted from a task while thinking of personal problems is an example of which type of human hazard factor?
Mental.
The weather-related hazards of climbing are: Rain, Wind and
Ice
While climbing, the hazard posed by bulky clothing is
getting snagged and losing your balance.
Some of the common elements of a fixed base are fixed
navigation systems, weather systems, and a permanent control tower.
At a fixed base, what must always be in the forefront of your mind?
Readiness to deploy and support the air and space expeditionary force (AEF) needs.
What determines the type of equipment used at a deployed base?
Mission of the base.
What is the most important part of being an air and space expeditionary force (AEF)
airman?
Being flexible and able to adapt to your surroundings.
Name the part of the AM signal that does not fluctuate in amplitude by the modulating signal.
The carrier.
What frequencies do the amplitude modulated waveform contains?
Unmodulated carrier frequency, USB, and LSB.
What part of the modulated carrier wave contains the information carrying component?
The sidebands.
In AM, what is the relation between the bandwidth required to transmit the signal and the frequency of the modulating signal?
The bandwidth required is two times the modulating signal frequency.
Define “percent of modulation”.
It refers to the amount of effect or change that the intelligence has on the carrier.
Find the % mod if a 4 Vpk-pk RF signal is modulated by a 2.5 Vpk-pk audio signal.
The percent of modulation is 62.5 percent—found by dividing 2.5 by 4 and multiplying the result by 100.
What are two results of over modulation?
Severe distortion and increases bandwidth of an AM signal.
How does the rate of deviation relate to the frequency of the modulating signal?
They are directly proportional.
What determines the amount of deviation of a FM carrier?
The amplitude of the modulating signal.
To prevent interferences with other FM stations, who establishes limits on the maximum amount of deviation in FM?
The FCC establishes the maximum amount of deviation.
What is a significant sideband?
A sideband that contains at least 1 percent of the total transmitted power.
How do you determine the modulation index in FM?
By dividing the amount of frequency deviation by the frequency of the modulating signal.
Where do FM sidebands get their power?
From the unmodulated carrier.
What is the relationship between modulation index and sideband power?
A higher modulation index means more power in the sidebands. It is even possible to have all the power in the sidebands and none in the carrier. At this point, any further increase in modulation would start taking power from the sidebands and placing it back in the carrier resulting in a redistribution of power.
In PM, what effect does the change in carrier frequency have?
None. The frequency change in PM is incidental.
Describe the effect the positive and negative alterations of a modulating signal have on the phase of the carrier in PM.
During the positive alternation of the modulating signal, the phase of the carrier lags behind the unmodulated carrier. During the negative alternation it leads the unmodulated carrier.
When is the carrier at its rest frequency in PM?
During the constant amplitude part of the modulating frequency.
What part of the modulating signal controls the amount of phase shift in PM?
Amplitude.
What part of the modulating signal controls the rate of phase shift?
Frequency.
Name the four steps of PCM (Pulse-code modulation)
Band limiting, sampling, quantizing, and encoding.
State the main purpose of the band-limiting filter.
It ensures the input to the sampler never exceeds a maximum frequency.
Define sampling.
Converting a continuous time signal into a discrete time signal.
What part of the pulse train is varied using PAM, PWM, and PPM?
PAM = amplitude; PWM – width or duration; PPM = position.
With ATM, what is the length of each transmission unit?
One character in length.
What part of an ATM transmission tells the receiving device that a character is coming and that the character has been sent?
The start and stop bits.
How does the receiving device determine whether it has received a correct character?
By summing the 1 bits. If the character arrives with an even number of 1 bits, the device assumes that it has received a correct character.
What is an advantage of synchronous transmission over asynchronous transmission?
To reduce the overhead costs of data transmission.
How does synchronous transmission differ from asynchronous transmission?
Synchronous transmission blocks many characters together for transmission.
What does VRC (Vertical redundancy Check) check each incoming character for?
Odd or even parity.
In LRC (Longitudinal Redundancy Check), what transmitted character does the receiver use to determine if a transmission was errorfree?
BCC (Block check character)
When using the checksum method of error detection, what binary number is used to divide the sum of all the characters in order to derive the checksum?
255.
How does the CRC method of error detection determine the dividend when computing the BCC?
CRC treats the binary ones and zeros in the frame address, control, and information fields as one long binary number.
How effective is CRC at detecting errors in most applications?
99 percent in most applications.
How does ARQ (Automatic transmit on request) work?
The receiver automatically sends a retransmitted request to the sender if it finds an error in a received frame.
Using forward error control, at which end of the transmission link are errors corrected?
Receiving end.
Using forward error control, what is the transmitter’s function in error correction?
To transmit multiple copies of the same message to the distant end.
Using forward error control, what is the receiver’s function in error correction?
To compare all copies of transmitted message, then reconstruct the message using the good portions of the message copies received.
When the modulating signal and carrier signal are combined within a modulator, the output signal contains
carrier, upper sideband, and lower sideband.
If a carrier frequency of 1 megahertz (MHz) and a modulating tone of 10 kilohertz (kHz) goes to the modulator, the output signal include:
1.01 MHz, 1 MHz, and 0.99 MHz.
The bandwidth of an amplitude modulation signal refers to the amount of
space the transmitted signal will occupy in the frequency spectrum.
If an oscilloscope displays a modulation envelope having an Emax of 200 volts and an Emin of 20 volts, what is the modulation percentage?
81.8.
Which statement concerning bandwidth is true?
A is Correct

A. Overmodulating increases bandwidth due to the production of harmonics.

b. Undermodulating increases bandwidth due to the production of harmonics.
c. Overmodulating increases bandwidth due to the output’s increased amplitude.
d. Undermodulating increases bandwidth due to the output’s decreased amplitude.
Reducing modulation to less than 100 percent gives
no reduction in carrier power.
The output of the oscillator in a frequency modulation (FM) modulator increases in
frequency with each
positive half cycle of the carrier.
In frequency modulation (FM), the amount of oscillator frequency change is
directly proportional to the amplitude of the modulating signal.
In frequency modulation, sidebands are considered significant when containing at least what percent of total transmitted power?
1% of transmitted power
What is the formula to find the modulating index?
Deviation divided by frequency of modulation.
A 5 kilohertz (kHz) modulating signal has enough peak voltage to cause a deviation of 15 kHz. What is the modulation index?
3
A narrow frequency band between adjacent stations to prevent frequency modulated
sidebands from overlapping is called
guard band.
What modulation technique is used especially for data transmission?
Phase
In phase modulation, the carrier’s
phase is shifted at the rate of the modulating signal.
In phase modulation, the amount of phase shift is
proportional to the amplitude of the modulating signal.
What is the first step in the pulse code modulation process?
The analog signal is band-limited.
What part of the pulse code modulation process converts a continuous time signal into a discrete time signal?
Sampling.
What type of pulse modulation changes the amplitude of the pulse train to vary according to the amplitude of the input signal?
Amplitude.
In asynchronous transmissions, what is used by the receiving device to verify that the
transmission was received correctly?
Parity bit.
If an error occurs in transmission, what data is lost in an synchronous transmission?
Block of data.
When using vertical redundancy check, the number of ones in a data bit pattern determines
parity.
When using the longitudinal redundancy check method of error correction, what does the receiver compare with the transmitter to ensure an accurate transmission of data?
Block check character.
What two error detection methods, when used together, are 98 percent effective in detecting errors?
Vertical redundancy check and longitudinal redundancy check.
What error detection method adds stacked characters, divides it by 255, and disregards the
answer except for the remainder?
Checksum.
What error-correction technique sends a retransmittal request by the receiver to the sender if it finds an error in a received frame?
Automatic retransmit on request.
Capabilities and limitations of AN/GRT–21/22

What determines the frequency, accuracy, and stability of the transmitter set?
The OSCILLATOR SYNTHESIZER.
Capabilities and limitations of AN/GRT–21/22

Name the modules that make up the APC circuit.
The power detector DC1, the A10, and the CONTROL RF/MODULATOR A6.
Capabilities and limitations of AN/GRT–21/22

What does the APC voltage do if the forward power gets too high?
Varies the gain of the A10 to normalize it.
Capabilities and limitations of AN/GRT–21/22

State the purpose of the E/L relay when operating the transmitter in the 10-watt mode.
The E/L RELAY has no purpose when operating in the 10-watt mode.
AN/GRT–21/22

Why does the UHF multiplier contain one more stage of amplification than the VHF version?
Because the fourth harmonic is weaker than the second harmonic.
AN/GRT–21/22

State the purpose of the transmitter’s tune/operate switch.
To protect the tunable filter during the tuning operation.
AN/GRT–21/22

What happens if the VSWR exceeds 3:1?
The E/L Relay is energized and the LPA is bypassed.
AN/GRT–21/22

Why are we concerned with removing the RF from the E/L relay when it energizes?
Momentarily removing the RF prevents arcing between the contacts of the relay.
Basic concepts of linear power amplifiers (LPA)

What is the purpose of the linear power amplifier?
To amplify the 10-watt output of the exciter to 50 watts.
Basic concepts of linear power amplifiers (LPA)

State the purpose of C1 and L1 in the A4 module.
To filter ripple out of the 2000VDC.
Basic concepts of linear power amplifiers (LPA)

In the A5 module, what are the LPA FWD and RVS power sensor voltages used for?
They are applied back to the exciter A6 module where they are used to develop the APC voltage and to detect VSWR(Voltage Standing Wave Ratio).
Basic concepts of linear power amplifiers (LPA)

State the purpose of the LPA tune/operate switch.
It decreases the exciter RF output to less than 10 watts out and it prevents the E/L relay from energizing.
In the AN/GRT–21 and AN/GRT–22, what circuit sets the audio frequency response?
Filter circuit in the A4 module.
In the AN/GRT–22 transmitter, the purpose of the E/L relay in a linear power amp (LPA)
when operating in the 50-watt mode is to
bypass the LPA in the event of high voltage standing wave radio (VSWR).
Comparing the AN/GRT–21 and AN/GRT–22, the Ultra-high frequency (UHF) multiplier module possess one more stage of amplification than the very high frequency (VHF) multiplier
because the
4th harmonic is weaker than the 2nd harmonic.
In the A10 module of the AN/GRT–21, the purpose of the TUNE/OPERATE switch is to
protect the tunable filter during tuning operation.
In the Control RF/Modulator A6 of the AN/GRT–21/22, if the 50-watt output decreases,
the conduction of Q3 increases, which causes a more positive alternate power control (APC) voltage.
In the Tuned Cavity (A7) of the linear power amp (LPA), C1 and C2 are tuned to pass what signal(s)?
Operating frequency only.
The linear power amp (LPA) forward (FWD) and RVS power sensor voltages are amplified and level-shifted in the LPA A5 module for what purpose?
Automatic power control (APC) voltage development and voltage standing wave ratio (VSWR) detection.
Why is it necessary for the RF amplifier section to isolate the local oscillator from the antenna?
If we connect the antenna directly to the mixer (frequency converter stage), a part of the oscillator signal might be radiated into space. This could cause interference for other receivers.
What is the difference between a mixer circuit and a converter circuit?
The mixer requires two input signals–the radio frequency and injection frequency. A converter has its own self-contained oscillator, and thus requires only one input signal—the radio frequency.
Define “image frequency.”
It is an undesired signal when mixed with the oscillator’s frequency, produces the correct IF. The image frequency is equal to the operating frequency ±2 IF.
Define demodulation.
The process of recovering intelligence from the modulated wave.
Briefly state the requirements for any type of demodulation.
The demodulator input circuit must be sensitive to the modulation characteristics. Nonlinearity must be present to cause heterodyning. An RF carrier signal must be present. Filtering is required to select the desired intelligence signal and reject the unwanted carrier.
What are the main drawbacks of using diode detectors?
Their main drawbacks are they provide no power gain and selectivity is affected by loading of the tank.
What factor determines the amount of amplification needed in the audio amplifier circuit?
The amount of amplification necessary depends upon the type of output device used. If the output device consists of earphones, only one stage of amplification may be necessary, if a large speaker is used, much more amplification may be necessary.
AN/GRR–23/24

Which module in the AN/GRR–23 and AN/GRR–24 performs the function of pre-selection?
The tunable filter, FL2.
AN/GRR–23/24

Which module determines overall receiver selectivity?
Crystal filter FL1.
AN/GRR–23/24

What happens to the DC portion of the detector output?
It is amplified and processed into the AGC voltage.
AN/GRR–23/24

In the UHF mixer/multiplier A2, to what frequency would Q1 be tuned if the oscillator
synthesizer’s output were 67.0 MHz?
Q1 would be tuned to the fourth harmonic—268MHz.
AN/GRR–23/24
In the UHF mixer/multiplier A2, what frequency will the output of transistor Q8 pass with an operating frequency of 321 MHz?
Regardless of the operating frequency, the output of transistor Q8 in the A2 module always passes the IF which is 20.6 MHz.
AN/GRR–23/24

In what section does most of the receiver’s amplification take place?
The IF section.
AN/GRR–23/24

What is the purpose of the receiver’s AGC circuit?
The AGC circuit provides a constant audio output with a varying RF signal strength.
AN/GRR–23/24

What is the purpose of the receiver’s squelch circuit?
To pass the audio if the RF at the antenna is of sufficient strength and block the audio output if the RF at the antenna is too weak.
Why can’t the antenna be connected directly to the mixer circuit?
The oscillator signal might be radiated out into space.
Which statements are true concerning receiver operation?
B is Correct

a. In order to change the operating frequency, we must change the intermediate frequency (IF) only.
B. When we change frequencies, the IF does not change, local oscillator frequency does.
c. Changing the local oscillator frequency has no effect on our operating frequency.
d. When we change frequencies, the IF changes by an amount equal to the change in the local oscillator frequency.
In what section of a super heterodyne receiver does most of the amplification
take place?
Intermediate frequency (IF) section.
Which section of the receiver determines overall selectivity?
Intermediate frequency (IF) filter.
What is the image frequency on a superheterodyne receiver with an operating frequency of
150 megahertz (MHz) and an intermediate frequency (IF) of 10.7 MHz?
171.4 MHz.
What are the AN/GRC–171 and AN/GRC–211 radios designed for?
Air traffic control communications sites for fixed and portable, point-to-point and ground-to-air communications.
How many channels are available when using the AN/GRC–171 and AN/GRC–211 radios?
The UHF version of the transceiver can communicate on any one of 7,000 available channels spaced 25 kHz apart in a range from 225 MHz to 399.975 MHz. The VHF version of the transceiver can communicate on any one of 1,440 available channels spaced 25 kHz apart from 116 MHz to 151.975 MHz.
What is the duty cycle for the AN/GRC–171 and AN/GRC–211 radios?
AN/GRC–171 (UHF)— 90 percent for transmit and continuous for receive; AN/GRC–211 (VHF)—continuous for transmit and receive.
Which version is more sensitive, UHF or VHF and why?
VHF, because of the RF PREAMPLIFIER.
AN/GRC–171/211

Where does the transmit RF originate?
FREQUENCY SYNTHESIZER A2.
AN/GRC–171/211

What is the purpose of the RF filter during transmit?
To eliminate harmonics.
AN/GRC–171/211

What are the characteristics of key 1 and key 2?
Key 1 – FASR; key 2 – SAFR.

FASR - Fast AttackSlow Release

SAFR - Slow Attack Fast Release
AN/GRC–171/211

What change does key 1 cause in the FREQUENCY SYNTHESIZER in the transition from transmit to receive?
It causes the frequency of the FREQUENCY SYNTHESIZER to shift its frequency up 30 MHz from the operating frequency in the AN/GRC–211 and down 30 MHz from the operating frequency in the AN/GRC–171.
AN/GRC–171/211

Describe the RF paths in the receive signal flow for UHF and VHF versions.
From the antenna through the RF FILTER MODULE A7 to the RF RECEIVER MODULE A3. The VHF version inserts a preamplifier between the A7 and the A3.
AN/GRC–171/211

What is the purpose of the RF filter during receive?
To eliminate image frequencies and provides preselection.
AN/GRC–171/211

What makes this a radio a dual conversion receiver?
The two mixers.
AN/GRC–171/211

the AN/GRC–211, where are the first and second IF produced?
The first is produced in the UHF mixer, and the second is produced in the second mixer.
AN/GRC–171/211

What is the frequency response of the HP and LP filters in the receive A4?
300 to 3,000 Hz.
AN/GRC–171/211

Which part of the radio converts the AC into an unregulated DC voltage?
Transformer/rectifier on the CHASSIS A10.
AN/GRC–171/211

Which part of the radio is a switching-type voltage regulator?
A6 module.
AN/GRC–171/211

Which input to the D/A SERVO AMPLIFIER MODULE A1 tells the servo where the filter is
tuned?
Position feedback (POSN FB) input.
AN/GRC–171/211

What would be the condition of the filter given the following conditions?
a. POSN FB = 4, Analog voltage = +6.
b. POSN FB = 4, Analog voltage = 6.
c. POSN FB = +4, Analog voltage = +6.
d. POSN FB = +4, Analog voltage = +4.
e. POSN FB = 4, Analog voltage = +4.
a. Tuning up.
b. Tuning down.
c. Tuning up.
d. Tuned.
e. Tuning down.
What is the output power of the AN/GRC–171 and AN/GRC–211?
20 watts for AN/GRC–171 and 25 watts for AN/GRC–211.
Sidetone in a transceiver radio is
a sample of the modulated radio frequency (RF) output.
Which is true of the AN/GRC–211?
There are separate receive and transmit audio amplifiers and filters.
Which keying options are for the AN/GRC–171?
Voltage, current, and ground keying.
During receive on an AN/GRC–171 transceiver
both keylines are high.
What makes the AN/GRC–171 and AN/GRC–211 dual conversion superheterodyne
receivers?
Two mixers.
What functions does the radio frequency (RF) FILTER A7 module perform during receive operation?
RF transmit-receive switch and attenuator.
What type of regulator(s) is (are) used in the AN/GRC–171?
One switching regulator and several series regulators.
Define “transmission line” and give an example of one.
A conductor or series of conductors used to carry energy from a source to a load. Examples include the flexible coaxial cable, the rigid coaxial cable, an AC power cord on a stereo, a cable television wire and a telephone cord.
What are some of the types of transmission line losses?
Resistive, skin effect, radiation, induction, capacitive, and leakage.
Name two methods of reducing induction loss.
The use of standoff insulators and shielded conductors.
What are the causes of major power losses in a flexible coaxial cable?
The dielectric and skin effect.
Why is there very little radiation loss in a rigid coaxial cable?
Because the energy is confined between the two conductors.
What determines ZO of a transmission line?
Its series inductance and shunt capacitance.
Identify the primary determinants of a line’s capacitance.
The amount of capacitance is primarily determined by the size of the conductors, the space between them, plus the dielectric material.
What does “cutoff frequency” refer to when we talk about transmission lines?
The frequency at which the value of XL and XC are such that the signal is developed across the series inductance and shunted by the capacitance and, thus, not passed along the line.
Define “wavelength.”
The distance in space occupied by one cycle of a radio wave at any given instant.
As signal frequency decreases, what happens to wavelength?
Wavelength increases.
What is electrical length?
Electrical length is a comparison of physical length and wavelength. We express electrical length in the number of wavelengths.

Each complete cycle = 1 wavelength; two complete cycles = 2 wavelengths, and so on.
What is the unit of measure for electrical length?
Meters.
What happens to electrical length as signal frequency decreases?
Changing the physical length of a transmission line has no effect on characteristic impedance.
Describe a nonresonant transmission line.
It is a line having no reflected waves.
What is an incident wave?
Voltage and current waves as they move from source to load.
What is a standing wave?
It is the vector sum of the forward and reflected waves.
Define “VSWR.”
This is a comparison (expressed as a ratio) of the maximum and minimum voltages found along the line.
If a transmission line has a perfect impedance match, what would the VSWR be?
1:1.
What is the voltage level at an open termination?
Voltage will be at maximum across an open.
What is the phase relationship between forward and reflected voltage waves when the line is terminated in a short?
Voltage is reflected 180 degrees out of phase.
What can you use to match a 50-ohm cable to a 600-ohm antenna?
A balun.
Which method of propagation is most dependent on the type of surface between the two antennas?
Surface-wave propagation.
What two components make up the space wave?
The ground-reflected wave and the direct wave.
Define “radiation angle.”
The angle above the horizon that an antenna radiates the largest amount of its RF energy.
What term defines two or more signals arriving at the receiver from different paths and interfering with each other?
Multipath interference.
Define “skip zone.”
It is an area between the longest ground-wave range and shortest sky-wave range where no signal exists.
Define “reciprocity.”
The ability of an antenna to both receive and transmit equally well.
If a wave is horizontally polarized, in what direction do the electric lines of force lie?
In a horizontal direction in a horizontally polarized wave.
What is an isotropic antenna?
A theoretical antenna that radiates equally well in all directions.
What is a drawback of using an omnidirectional antenna?
It is susceptible to interference from any direction.
How can we reduce interference and interaction when using a bidirectional antenna?
By placing other antennas in the “nulls” of the bidirectional antenna.
What is the relationship between “directivity” and “radiation angle”?
There is no relationship!!! Duh!
With no accessory kit, what is the maximum power that an AN/GRA–4 can handle?
100 watts.
Why are vertical antennas practically useless in areas of dense vegetation?
Because the ground wave is absorbed by the surrounding growth and the sky waves are very weak.
Which antenna type operates over a wide range of frequencies and exhibits essentially constant characteristics over this entire range?
The log-periodic antenna.
What type of antenna can we use to determine the location of a transmitter?
A direction-finding antenna.
What is the purpose of an antenna coupler?
To match the equipment to the transmission line and antenna.
How many channels can one CU–547/GR support?
Up to four channels.
State the purpose of relays A1A1K1 and A2K2 in the antenna coupler example used in our text?
To bypass the tuning elements and provide an RF path when the coupler is not tuned to a specific transmitting frequency.
What happens in an antenna coupler if the VSWR exceeds 2:1?
The logic circuits react by disabling the keying circuit, after which the tuning cycle must be repeated.
The amount of skin-effect loss is directly proportional to the
signal frequency.
Which type of transmission line loss can you minimize by using a hollow conductor?
Skin-effect.
Leakage loss in a transmission line can be minimized by using a
very high-resistance dielectric.
Which frequency best describes the term “cutoff frequency” when discussing transmission line properties?
The frequency where XC causes the signal to be shunted.
Which statement concerning wavelength is true?
Wavelength is inversely related to frequency.
A nonresonant transmission line is a line
having no reflected waves.
On a transmission line with an open termination, the wave is reflected back to the source and
there would be significant signal loss.
The purpose of a Balun is to:
provide an impedance match between transmission line and an antenna
What type of interference is caused when two or more signals of the same frequency arrive at the receiver simultaneously?
Multi-path.
If an antenna’s electric lines of force lie in a vertical direction, it can be said that the
antenna is
vertically polarized.
An antenna that radiates well in all directions is said to be
omnidirectional.
An antenna that concentrates a strong signal in one direction while the signal is reduced in other directions is called
unidirectional.
Using an antenna and associated equipment to determine the location of an radio frequency (RF) source is the definition of
Using an antenna and associated equipment to determine the location of an radio frequency (RF) source is the definition of
How many channels can be connected to the CU–547/GR antenna multicoupler?
4
When using the CU–2310 antenna coupler, a voltage standing wave ratio (VSWR)
exceeding 2:1 causes
the keying circuit to be disabled and the tuning cycle must be repeated.
Fluke 8025A Multimeter

Which control do you use to select the meter’s different measurement functions?
The rotary switch.
Fluke 8025A Multimeter

List the four types of information presented in the multimeter’s display section.
(1) Digital display.
(2) Visual annunciators.
(3) Analog bar graph.
(4) Range indicator.
Fluke 8025A Multimeter

Which information in the display section shows the absolute value of the input?
Analog bar graph.
Fluke 8025A Multimeter

Describe the function of the range push button.
The range push button lets you manually select the measurement range.
Fluke 8025A Multimeter

What is the purpose of the touch-hold push button?
The touch-hold push button locks the measurement into the display for viewing and automatically updates the display when you take a new measurement.
Fluke 8025A Multimeter

List the multimeter’s four input jacks.
(1) Amperes.
(2) Milliamps/microamps.
(3) Volts/ohms/diode.
(4) Common.
Fluke 8025A Multimeter

When does the 8025A perform a power-up self test?
When you move the rotary switch to any position from the OFF position.
Using the Fluke 8025A Multimeter

What two ranges of DC voltages can you measure using the 8025A multimeter?
−1,000 to +1,000 volts DC; −320 to +320 millivolts DC.
Using the Fluke 8025A Multimeter

What is the maximum amount of continuous AC current that you can measure with the
multimeter?
10 amps.
Using the Fluke 8025A Multimeter

When using the Fluke 8025A, how do you know you’re in the resistance measurement function?
The Ω annunciator is showing in the display.
How do you determine if you’re testing a “good” diode with the 8025A?
Placing the leads across a “good” diode produces “OL” in the display while reversing the leads produces a continuous audible tone.
What type of display does the oscilloscope present?
Amplitude vs time.
On which axis of an oscilloscope is voltage, time, and depth information presented?
Voltage = vertical axis
Time = horizontal axis,
Depth = intensity.
What is the purpose of the delay line at the input of the vertical amplifier?
It allows the sweep generator circuitry time to start a sweep before the signal reaches the cathode ray tube vertical deflection plates. This enables you to view the leading edge of the signal waveform.
What position of the input coupling switch is used to view digital-type or square wave signals?
DC coupling.
What is the basic purpose of the oscilloscope probe?
To provide isolation for scope inputs and prevent circuit loading.
List four types of probes?
(1) The high resistance.
(2) Passive divider and x1 probes.
(3) Active (field effect transistor).
(4) Current probes.
What is the typical input impedance of most oscilloscopes?
One megaohm shunted by 20 pF of capacitance.
When making an amplitude measurement and the source impedance is unknown, greatest accuracy is achieved when the probe’s Z is what?
Highest (maximum).
Why do we test ground?
To verify the ground-resistance specification that the ground rod or grid must meet.
What test equipment is used to identify poor ground?
Earth ground tester.
What is the name of the test method used in the Fall of Potential testing?
The three test method.
What is each point of contact called in the Fall of Potential testing method?
The test ground, voltage probe, and current probe.
At what distance represents the closest value to the theoretical true resistance measurement?
61.8% of the total distance.
How is the earth stakes placed in the soil?
In a direct line away from the earth electrode.
Which law is used to calculate the resistance of the earth electrode automatically with the earth ground tester?
Ohm’s Law.
Where are the probes placed in order to achieve the highest degree of accuracy?
Placed outside the sphere of influence of the ground electrode under test and the auxiliary earth.
What is the recommended ground resistance value by the NFPA and IEEE?
5 ohms or less.
Radio frequency signal generator

What is the frequency range of the HP 8640B radio frequency signal generator?
500 kHz to 512 MHz (450 kHz to 550 MHz with over-range).
Radio frequency signal generator

What extends the HP 8640B range from 20 Hz to ultra high frequencies?
A variable audio oscillator can extend the output range of the generator down to 20 Hz and a doubler can extend it to 11,000 MHz. This, together with a calibrated output and modulation, permits complete radio frequency and intermediate frequency performance tests on virtually any type of high frequency, very high frequency, or ultra high frequency receiver.
Radio frequency signal generator

What is the function of the oscillator section?
To produce a signal that can be set accurately in frequency at any point within the range of the generator.
Radio frequency signal generator

What is the function of the modulator?
To produce an audio modulating signal to superimpose on the radio frequency signal produced in the oscillator.
Radio frequency signal generator

What types of modulated signals are possible with the radio frequency generator?
Either sine waves, square waves, or pulses of varying duration.
Radio frequency signal generator

What does the output circuit of the radio frequency signal generator usually contain, and what are their functions?
A calibrated attenuator and an output level meter.

The attenuator lets you select the amount of output required.

The output level meter provides an indication and permits control of the generator output voltage.
Radio frequency signal generator

List some applications of the radio frequency generator.
(1) Verify transmission within designated frequency ranges by comparing transmitter outputs with known radio frequencies.
(2) Align a receiver by injecting the system with range-standard modulated radio frequency.
(3) Check transmission lines and antenna systems for proper operation.
Defining the terms dB and dBm

The decibel is part of what larger unit of measure?
Bel.
Defining the terms dB and dBm

A power ratio of 10,000:1 can be represented by how many bels?
4
Defining the terms dB and dBm

What’s the most commonly used industry standard power reference level?
The 1-milliwatt standard.
Defining the terms dB and dBm

What will every 3 dB increase in gain do to the power level?
Roughly double it.
Defining the terms dB and dBm

How many dB of gain does an amplifier have if there are 10 watts in and 80 watts out?
There’s a gain of 9 dB.
Defining the terms dB and dBm

You have installed an in-line 3 dB attenuator between a power source and the power sensor of a power meter. How will this affect the power level displayed by the power meter?
It will cut it in half.
Defining the terms dB (decibel) and dBm

What two power characteristics are reflected by the term dBm?
Gain and power level.
Defining the terms dB and dBm

How do the terms dB and dBm differ?
Because dBm is always referenced to a 1-milliwatt standard, it can be used to reflect a power level, in addition to gain or loss. The term dB can’t reflect a power level; instead, it can only reflect gain or loss
because it’s purely a ratio.
Defining the terms dB and dBm

How much more power is available at 6 dBm than at 3 dBm?
Twice as much.
What power levels are indicated by these measurements?
(a) 3 dBm.
(b) 9 dBm.
(c) 12 dBm.
(d) 36 dBm.
(a) 2 mW.
(b) 8 mW.
(c) 16 mW.
(d) 4,096 mW (approx 4.1 watts).
List at least three of the units that can be displayed by the HP 436A power meter.
(1) Watts.
(2) Milliwatts.
(3) Microwatts.
(4) Nanowatts.
(5) DBm.
(6) Relative dB
Briefly explain how to use the relative power measurement mode for frequency response testing.
After the input is connected, press dB(REF) to lock in this frequency level as the reference, then tune the transmitter to other frequencies and observe any changes up or down in the power level.
What is the 4391M RF Power Analyst designed to measure?
The power flow, load match, and AM in 50 ohm coaxial transmission lines.
What are the two switches on the front panel of the 4391M RF Power Analyst used for?
Two switches on the front panel of the instrument are set by the user to correspond to the power range of the forward element.
If only the forward element is used, what is filled in the other socket of the 4391M RF Power Analyst?
With a dust plug or a higher power element.
When reading forward power, what will be displayed if the applied power exceeds 120% of the range on the 4391M wattmeter?
If the applied power exceeds 120% of the range, two right facing arrow heads will be displayed.
Where is the reflected CW reading taken on the 4391M wattmeter?
From the element in the socket marked “reflected.”
Between what power ranges will a SWR be displayed on the 4391M wattmeter?
SWR will be displayed if the average forward power is between 10% and 120% of the full scale and the average reflected power is less than 120% of the reflected element range.
What is the difference in readings CW and PEP on the 4391M wattmeter?
Readings are displayed directly as peak power in PEP. To formulate CW power, the wattmeter measures peak and minimum square root of power and combines them.
How is over-modulation displayed on the 4391M wattmeter?
Over-modulation will be indicated as 99.9%.
What must be added to the dBm reading when the range is in kilowatts on the 4391M wattmeter?
30 must be added to all dBm readings when the range is in kilowatts.
When measuring return loss, what does a reading of 21.6 indicates on the 4391M wattmeter?
The measurement of return loss reading of 21.6 indicates that reflected power is 21.6 dB down from forward power.
In order to recall the maximum reading, what key do you press on the 4391M wattmeter?
To recall the maximum reading, hold the MAX or MIN key down.
How do you clear the minimum and maximum register on the 4391M wattmeter?
To clear the minimum and maximum register, the mode key must be pressed again or a new selected.
Which mode on the 4391M Wattmeter is useful for making adjustments to optimize any of the parameters which the
wattmeter measures?
Peaking aid.
What is a major difference between the oscilloscope and the spectrum analyzer?
The oscilloscope displays frequency information in the time domain, whereas the spectrum analyzer displays frequency information in the frequency domain.
Describe how the spectrum analyzer displays information in the frequency domain.
By complex signals (i.e., signals composed of more than one frequency) that are separated into their frequency components, and the power level of each frequency is displayed.
What functions does the spectrum analyzer perform?
(1) Locate and identify signals over a wide frequency spectrum.
(2) Magnify parts of the spectrum for detailed analysis with stable, calibrated sweeps and resolution.
(3) Minimize display clutter for spurious responses within itself.
(4) Furnish wide dynamic range and flat frequency response.
What advantage do the spectrum analyzer’s sensitivity and wide dynamic range provide?
A way to measure low-level modulation.
List some uses of the spectrum analyzer.
(1) Measure AM, FM, and pulsed radio frequency.
(2) Measure long- and short-term frequency stability.
(3) Measure parameters such as subcarrier oscillator outputs, channels of complex signals.
(4) Measure frequency drift during system warm-up.
What is the frequency range of an electronic frequency counter?
Low audio frequencies up to 550 MHz. Some methods are available to extend the frequency range of counters to more than 20 GHz.
What provides the time reference for the precise timing and where does this function take place in the electronic frequency counter?
A quartz-crystal oscillator inside the counter.
Portable instrument landing system and very high omni range receiver

The PIR consists of?
The PIR electronics, LOC/GS antenna assemblies, a battery assembly, and a 12-volt DC power supply.
Portable instrument landing system and very high omni range receiver

The PIR accessories kit consists of?
A carrying case, antennas, cables, adapters, monopod support, and power supply.
Portable instrument landing system and very high omni range receiver

The digital portion of the PIR consists of?
Five seven-segment digits with decimal points between segments.
Portable instrument landing system and very high omni range receiver

When is a 30 dB attenuator placed in line with the RF input of a PIR?
Levels known to be greater than 10 dBm.
Vector Voltmeter

What is the primary importance to remember when using the Vector Voltmeter?
Do not exceed the maximum input voltage rating and handle the probes with care.
Vector Voltmeter

What is the phase finder?
Overrides PHASE RANGE and PHASE METER OFFSET to select the +/-180 degree phase range and zero offset. Used to find phase angle without changing settings of controls.
Techniques for cleaning electronic equipment are followed in which technical order?
TO 00–25–234.
Care of TMDE is in which technical order?
TO 00–20–14, Air Force Metrology and Calibration Program.
Which feature of the Fluke 8025A multimeter do you use to select various measurement functions?
Rotary switch.
Which part of the Fluke 8025A’s display section indicates the absolute value of the input?
Analog bar graph.
When you use the Fluke 8025A, which voltage range do you select to measure 50 volts direct current (DC)?
Volts DC.
Which current range on the Fluke 8025A do you select to measure 250 milliamps
alternating current (AC)?
Milliamps/amp AC.
When testing a diode with the Fluke 8025A, the leads across a “good” diode produces an
“OL” (open) on the display in one direction while reversing the leads produces
a continuous audible tone.
On the screen of the oscilloscope, what type of information is not displayed?
Frequency.
What control lets the operator select many different sweep speeds in order to view
waveforms in the oscilloscope?
Time/division (time/div).
Which oscilloscope probe is essentially just a shielded piece of wire?
Passive 1:1 probe.
Which probe lets you use the oscilloscope to measure higher voltage levels, raises the input impedance, does not require a bias voltage, and attenuates noise?
Passive divider, 10:1 probe.
Which probe on the oscilloscope does not need to actually make contact with the circuit under test?
Current probe.
How often should you test a ground rod?
Periodically
What type of equipment helps resolve intermittent electrical problems due to poor
grounding?
Earth ground tester.
What ground testing method makes contact with the soil using the test electrode, plus the current and potential probes?
Fall of potential.
Resistance reading on the ground under test are plotted on a graph of
resistance versus distance.
What is the first step in testing a ground?
Disconnect the earth electrode under test from its connection to the site.
Where is voltage potential measured in the fall of potential ground testing method?
Between the auxiliary potential electrode and the earth ground electrode.
Which application is not a radio frequency generator?
Verifying transmitter frequencies.
A radio frequency generator is used to
align telemetry receivers.
The 10:1 power ratio represented by 1 bel can also be represented by how many decibels
(dB)?
10 dB.
A power reading that uses the abbreviation dBm indicates the
ratio of decibels relative to a 1-milliwatt standard.
When transmitter power is doubled, the decibels (dB) has increased by
3dB
During what operation is the radio frequency blanking output used on the HP 436A power meter?
During the automatic zeroing operation.
Plug-in elements of the wattmeter are selected based on the
frequency and power to be measured.
When reading forward power on a wattmeter, what does the two right facing arrow heads mean?
Power exceeds 120 percent of the range.
Which measurements is not made with a spectrum analyzer?
Peak-peak voltage is NOT measured with a spectrum analyzer...
Which electronic counter measurement represents the average bit-to-bit time of an input signal?
Period.
Which electronic counter measurement counts the number of bits in a pulse train?
Totalize
Which are the correct four classes of electronic counters?
Frequency counters, universal counters, microwave counters, and reciprocal counters.
The portable instrument loading system (ILS) receiver (PIR) is powered by?
7.2 Volts DC.
Localizer and Glideslope frequencies are programmed in the portable instrument loading system (ILS) receiver (PIR) as
pairs
The vector voltmeters most accurate phase meter sensitivity is
+/–6 degrees.
The maximum input voltage for a vector voltmeter should be limited to how many Volts
Root Mean Square (VRMS)?
1.5.
Which technical order best describes the care of test measurement and diagnostic
equipment (TMDE)?
00–20–14
What effect can roughness or sloping terrain around an instrument landing system have on the radiation pattern?
It can prevent the formation of the desired radiation pattern and produce an undesirable course.
What is the maximum transverse tilt allowed in area B in front of the localizer course array?
Transverse tilt (perpendicular to on-course line) must not exceed 1:100.
What are the restrictions on objects in a 30 sector in front of the localizer course array?
In a 30 sector in front of the course array, the height of objects must be below a slope line, running from the array, of 1:100.
What are the restrictions on the area within 500 feet in front of the glideslope antenna?
Must be clear of vehicular traffic and other reflecting objects.
How do you get power and control lines to an omnirange shelter?
They run underground radially from the terminal pole for at least 2,000 feet from the shelter.
Why are objects beyond 1,000 feet not critical in the siting criteria for a TACAN?
They cause shadows, but do not cause substantial errors.
How far from the digital wind sensor must a building that’s 25 feet across and near the height of the sensor be located?
Potential obstructions beyond the 2 foot radius should comply with distance-to-diameter ratio of 10—in this case, 250 feet.
What are the 7 career fields under Cyber Systems?
Client Systems (3D1X1)
Cyber Transport Systems (3D1X2)
RF Transmission Systems (3D1X3)
Spectrum Ops (3D1X4)
Radar Systems (3D1X5)
Airfield Systems (3D1X6)
Communications Cable and Antenna Systems (3D1X7).
What agency periodically inspects the safety of the navigational equipment?
Federal Aviation Administration.
For the instrument landing system (ILS) localizer, area A’s surface roughness should not exceed
+/- 0.5 feet.
For the instrument landing system (ILS) localizer, area B’s surface roughness should not exceed
 2 feet.
For the instrument landing system (ILS) glide slope, area A’s surface roughness should not exceed
Plus or Minus +/- 0.5 feet.
For the instrument landing system (ILS) glide slope, area B’s surface roughness should not exceed
 2 feet.
A 4-foot diameter obstruction at the same elevation as the AN/FMQ–13, Digital Wind
System, sensor must be located at least how many feet from the sensor?
40 feet.
Which career field is not part of the Cyber Systems (3D1)?
C. is not part of 3D1!

a. Radar Systems.
b. Spectrum Operations.
C. Cyber Space Systems.
d. Radio frequency (RF) Transmission Systems.
Which agency periodically inspects flight safety?
Federal Aviation Administration.