ATT Test 7 (Latest 2024/ 2025 Update) Questions and Verified Answers| 100% Correct| Grade A
ATT Test 7 (Latest 2024/ 2025 Update)
Questions and Verified Answers| 100%
Correct| Grade A
Q: Which type of multivibe circuit is free running?
Answer:
Astable
Q: What components are in feedback circuit (Astable)?
Answer:
Two capacitors
Q: What components are in feedback circuit (monostable)?
Answer:
One capacitors and one resistor
Q: What components are in feedback circuit (bistable)?
Answer:
Two capacitors, two resistors
Q: How is output determined in astable multivibe?
Answer:
Determined by feedback circuit
Q: Which transistor conducts first in astable multivibe?
Answer:
Whichever reaches 0.6V first (Vcc applied, pos volts on Q1/Q2 base)
Q: With Q1 ON (0v), how is Q2 turned off? (Astable)
Answer:
C1 discharging puts negative charge to Q2 base
Q: With Q1 ON (0V), how is Q2 turned ON? (Astable)
Answer:
C1 charging increases volts Q2 base
Q: With Q2 ON (0V), how is Q1 turned OFF? (Astable)
Answer:
C2 discharging puts negative charge to Q1 base
Q: With Q2 ON (0V), how is Q1 turned ON? (Astable)
Answer:
C2 charging increases volts Q1 base
Q: What is another name for monostable multivibe?
Answer:
One Shot
Q: How is frequency determined in monostable multivibe?
Answer:
Output frequency = Input frequency
Q: How is Q1 turned on (monostable)?
Answer:
Input pulse forward biases D1 and is applied to Q1 base
Q: What happens when Q1 turns on (monostable)?
Answer:
C1 discharges and turns OFF Q2 (12V)
Q: When Q1 is ON, what causes it to turn OFF? (monostable)
Answer:
C1 charges enough to turn Q2 ON which turns Q1 off
Q: How is frequency determined in bistable multivibes?
Answer:
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What is the purpose of multivibrators? Convert DC ENERGY into SQUARE WAVE ENERGY
How are transistors biased in multivibrators? To be in EITHER saturation or cutoff, NEVER inbetween
What component determines which transistor is ON or OFF in multivibe circuit? Feedback circuit
What does it mean when a transistor is ON? How many volts on collector? Saturation (MAX current flow), 0 V
What does it mean when a transistor is OFF? How many volts on collector? Cutoff (no current flow), 12 V
If both transistors have outputs (multivibe), what is phase shift between them? 180
Which type of multivibe circuit is free running? Astable
What components are in feedback circuit (Astable)? Two capacitors
What components are in feedback circuit (monostable)? One capacitors and one resistor
What components are in feedback circuit (bistable)? Two capacitors, two resistors
How is output determined in astable multivibe? Determined by feedback circuit
Which transistor conducts first in astable multivibe? Whichever reaches 0.6V first (Vcc applied, pos volts on Q1/Q2 base)
With Q1 ON (0v), how is Q2 turned off? (Astable) C1 discharging puts negative charge to Q2 base
With Q1 ON (0V), how is Q2 turned ON? (Astable) C1 charging increases volts Q2 base
With Q2 ON (0V), how is Q1 turned OFF? (Astable) C2 discharging puts negative charge to Q1 base
With Q2 ON (0V), how is Q1 turned ON? (Astable) C2 charging increases volts Q1 base
What is another name for monostable multivibe? One Shot
How is frequency determined in monostable multivibe? Output frequency = Input frequency
How is Q1 turned on (monostable)? Input pulse forward biases D1 and is applied to Q1 base
What happens when Q1 turns on (monostable)? C1 discharges and turns OFF Q2 (12V)
When Q1 is ON, what causes it to turn OFF? (monostable) C1 charges enough to turn Q2 ON which turns Q1 off
How is frequency determined in bistable multivibes? Output frequency is 1/2 Input frequency
If Q1 conducts first (ON 0V), how is Q2 turned OFF? (bistable) Negative volts on Q2 base coupled through capacitor
With Q1 ON, how is Q1 turned OFF? (Bistable) Negative pulse from INPUT forward biases D1, negative signal turns Q1 OFF
With Q1 OFF, how is Q2 turned ON? (Bistable) !2V on Q1 collector coupled to Q2 base by capacitor
What is troubleshooting procedure for astable multivibes? Check output, Vcc, transistors, resistance checks
What is troubleshooting procedure for monostable/bistable multivibes? Check output, input trigger, Vcc, transistors, resistances
What is the purpose of a schmitt trigger? Convert ANY shape waveform into square wave pulses of CONSTANT amplitude
Schmitt trigger is also called what other names? Squaring amp, level detector, threshold detector
What determines upper threshold in schmitt trigger? Voltage divider
What happens when upper threshold is reached? Q1 approaches saturation (ON) and drives Q2 into cutoff (high output)
What ensures very short rise/fall times in schmitt trigger? Feedback circuit
What turns Q2 on in schmitt trigger? Vcc
How is low output formed schmitt trigger? Volt divider formed between R6 and R8, 0V on Q2 collector causes low voltage drops
What is frequency range of AM? 535kHz to 1605 kHz
Voice, music, coded signals are all types of what? Intelligence (Information)
What is modulation? The process of superimposing waveform onto RF carrier (low frequency audio signal on high frequency carrier)
What is a benefit of modulation? Reduces necessity for long antennas
What is demodulation? Process of extracting intelligence from carrier frequency
What is noise? Any unwanted disruption/variation that contaminates modulated carrier
What are three types of noise? Man-made, atmospheric, galactic
What is distortion? Degradation of signal, commonly resulting from overdriven amps. Clipped or flattened peaks
What is selectivity? Receivers ability to tune to specific frequency and reject unwanted frequencies
What is sensitivity? Receivers ability to correctly reproduce weak signals
What is wave propagation? Movement of electromagnetic waves through medium
What are two types of waves? Longitudinal and transverse
What are two types of transverse (electromagnetic) waves? Radio and light waves
What is the most important region of stratosphere for long distance, point to point comms? Ionosphere (31 to 250 miles above sea level)
What layer of ionosphere disappears after sunset? D-layer
What layer of ionosphere has longest propagation capability? F layer
What are 4 factors that affect refraction? Ionization, layer density, RF freq, penetration angle
What is critical angle? Max angle at which radio wave can be transmitted and still be refracted back to earth?
What is skip zone? zone of silence between the point where the ground wave becomes too weak for reception and the point where the sky wave is first returned to Earth
What are two types of ground waves? Surface, direct
Skipzone is (lengthened/shortened) at night? Lengthened (bigger area of silence)
Skip zone is (lengthened/shortened) during the day? Shortened (smaller area of silence)
As frequency increases, the critical angle must _? Decrease
Which frequency has least amount of problems? Optimum Working Frequency (owf)
What is the purpose of Amplitude modulation? Transmit over longer distances
What is main purpose of AM receiver? Pickup electromagnetic waves/restore original low frequency intelligence (RECEIVE RADIO WAVES)
What 4 things do AM receivers perform? Reception, selection, detection, reproduction
What are 4 parts of AM receiver block diagram? Tuner, IF amp, detector, AF amp
What is purpose of tuner? Converts received RF into IF (intermediate frequency)
What is the purpose of IF amp? Amplify IF from tuner
What is purpose of detector? Recover original audio from IF signal
What is purpose of AF amp? increases detected audio enough to drive speaker
What is LO? IF + RF (set 455kHz above received signal)
What 3 circuits are in tuner? RF amp, mixer, local oscillator
What is IF? 455kHz (LO – RF)
What 4 things does mixer produce? RF, LO, Sum (RF+LO), IF (LO-RF)
What circuits make up detector? Rectfier, RC circuit
What does rectifier circuit do? Eliminates pos or neg audio signal from carrier
What does RC circuit do? Removes carrier from low freq audio
What circuits make up AF amp? pre-amp, driver, PUSH-PULL amp
Which part of AM receiver provides AVC? Detector
All stages of IF amp are tuned to what? 455kHz (IF)
What is the purpose of AVC? Keeps volume constant
What is purpose of T6 in push-pull amp (AF amp)? Provides push-pull amp with two signals 180 degrees out of phase
What frequency is C1A tuned to? RF
What signal is C1B tuned to? LO (LF+RF)
What frequency is T2 tuned to (Tuner)? LO
What frequency is T3 tuned to (tuner)? IF
What 3 functions do Q1 perform? Amp, mixer, oscillator
What type of signal is AVC? Negative signal
What is purpose of T7? (AF amp) Speaker driver