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Questions and Answers
What is the primary function of the CERAMIC BANDPASS FILTER block in the procedure?
What is the primary function of the CERAMIC BANDPASS FILTER block in the procedure?
- To amplify the audio signal
- To pass the upper sideband while blocking the lower sideband (correct)
- To ensure the output signal has constant amplitude
- To modulate the audio frequency signal
Which initial condition does NOT need to be satisfied before powering on the ANACOM 1/1 board?
Which initial condition does NOT need to be satisfied before powering on the ANACOM 1/1 board?
- AUDIO INPUT SELECT switch in INT position
- OUTPUT AMPLIFIER’s GAIN preset in fully clockwise position
- SPEAKER switch in ON position (correct)
- MODE switch in SSB position
What happens to the waveform at t.p.20 after passing through the CERAMIC BANDPASS FILTER block?
What happens to the waveform at t.p.20 after passing through the CERAMIC BANDPASS FILTER block?
- It shows random fluctuations in amplitude
- It changes to a square wave form
- It becomes distorted by external noise
- It appears as a good, clean sine wave (correct)
What adjustment can be made to vary the modulating frequency of the audio signal?
What adjustment can be made to vary the modulating frequency of the audio signal?
What does the output signal at t.p.20 reveal about the performance of the CERAMIC BANDPASS FILTER?
What does the output signal at t.p.20 reveal about the performance of the CERAMIC BANDPASS FILTER?
What initial position should the BALANCE preset be set to before monitoring outputs?
What initial position should the BALANCE preset be set to before monitoring outputs?
How does changing the modulating frequency affect the amplitude of the signal at the output of the CERAMIC BANDPASS FILTER?
How does changing the modulating frequency affect the amplitude of the signal at the output of the CERAMIC BANDPASS FILTER?
What is the purpose of examining the waveforms in the BALANCE MODULATOR & BANDPASS FILTER CIRCUIT 1 block?
What is the purpose of examining the waveforms in the BALANCE MODULATOR & BANDPASS FILTER CIRCUIT 1 block?
Which preset position should the AUDIO OSCILLATOR’s AMPLITUDE be in for proper conditions on the ANACOM 1/1 board?
Which preset position should the AUDIO OSCILLATOR’s AMPLITUDE be in for proper conditions on the ANACOM 1/1 board?
What is the required setting for the MODE switch on the ANACOM 1/1 board?
What is the required setting for the MODE switch on the ANACOM 1/1 board?
What should the OUTPUT AMPLIFIER's GAIN preset be set to on the ANACOM 1/1 board?
What should the OUTPUT AMPLIFIER's GAIN preset be set to on the ANACOM 1/1 board?
When the AMPLITUDE preset is turned fully counter-clockwise, what happens to the monitored output signal from ANACOM 1/1?
When the AMPLITUDE preset is turned fully counter-clockwise, what happens to the monitored output signal from ANACOM 1/1?
In order to monitor the I.F. AMPLIFIER 2 output on the ANACOM 1/2 module, what should you adjust?
In order to monitor the I.F. AMPLIFIER 2 output on the ANACOM 1/2 module, what should you adjust?
What must be ensured about the RX INPUT SELECT switch for proper operation?
What must be ensured about the RX INPUT SELECT switch for proper operation?
What effect does touching ANACOM 1/1’s antenna have on the SSB waveform at t.p. 13?
What effect does touching ANACOM 1/1’s antenna have on the SSB waveform at t.p. 13?
What is the correct position for the AGC switch on the ANACOM 1/1 board?
What is the correct position for the AGC switch on the ANACOM 1/1 board?
What is the result of adjusting the CARRIER FREQUENCY preset to 450 kHz?
What is the result of adjusting the CARRIER FREQUENCY preset to 450 kHz?
What should be monitored at t.p.52 when varying the frequency of the signal generator?
What should be monitored at t.p.52 when varying the frequency of the signal generator?
When applying the output from the Foster-Seeley block to the LOW PASS FILTER, what component should be removed?
When applying the output from the Foster-Seeley block to the LOW PASS FILTER, what component should be removed?
How is the FM signal modulated in this experiment?
How is the FM signal modulated in this experiment?
What is the amplitude of the sinusoidal output used to test the Foster-Seeley detector?
What is the amplitude of the sinusoidal output used to test the Foster-Seeley detector?
What is observed at t.p.14 during the monitoring phase?
What is observed at t.p.14 during the monitoring phase?
What effect does applying a 2 kHz noise signal have on the FM signal?
What effect does applying a 2 kHz noise signal have on the FM signal?
What should the curve represent when plotting DC level against frequency after varying the signal generator's frequency?
What should the curve represent when plotting DC level against frequency after varying the signal generator's frequency?
What must be adjusted in MODULATOR 2 to achieve equal amplitude of frequency components in the DSK signal?
What must be adjusted in MODULATOR 2 to achieve equal amplitude of frequency components in the DSK signal?
What frequency corresponds to a data bit value of ‘1’ in the FSK signal?
What frequency corresponds to a data bit value of ‘1’ in the FSK signal?
What effect does the higher incoming frequency have on the output voltage of MODICOM 5/2’s FSK DEMODULATOR?
What effect does the higher incoming frequency have on the output voltage of MODICOM 5/2’s FSK DEMODULATOR?
What is the main purpose of the low pass filtering stage in the demodulation process?
What is the main purpose of the low pass filtering stage in the demodulation process?
What adjustment is necessary for the output pulses of COMPARATOR 1 to match the pulse width of MODICOM 5/1’s NRZ(L) output?
What adjustment is necessary for the output pulses of COMPARATOR 1 to match the pulse width of MODICOM 5/1’s NRZ(L) output?
What should happen after turning on MODICOM 3/1’s SYNC CODE GENERATOR?
What should happen after turning on MODICOM 3/1’s SYNC CODE GENERATOR?
When using function generators with MODICOM 3/1, what does the user check at MODICOM 3/2’s analog outputs?
When using function generators with MODICOM 3/1, what does the user check at MODICOM 3/2’s analog outputs?
What is the end result of frequency modulation by MODICOM 5/1’s NRZ(L) output?
What is the end result of frequency modulation by MODICOM 5/1’s NRZ(L) output?
What is the effect of increasing the sampling frequency on the ability to reconstruct the original waveform?
What is the effect of increasing the sampling frequency on the ability to reconstruct the original waveform?
How does varying the sampling duty cycle affect the output amplitude of the filter in a practical digital communications system?
How does varying the sampling duty cycle affect the output amplitude of the filter in a practical digital communications system?
What is the primary purpose of the sample/hold circuit in a digital communications system?
What is the primary purpose of the sample/hold circuit in a digital communications system?
When comparing the outputs of the Second Order Low Pass Filter and Fourth Order Low Pass Filter, what factor is being analyzed?
When comparing the outputs of the Second Order Low Pass Filter and Fourth Order Low Pass Filter, what factor is being analyzed?
At what sampling frequency does the amplitude of the filter output become equal to that of the original analog input?
At what sampling frequency does the amplitude of the filter output become equal to that of the original analog input?
What happens to the filter output signal as the sampling frequency is changed using the FREQUENCY SELECTOR switch?
What happens to the filter output signal as the sampling frequency is changed using the FREQUENCY SELECTOR switch?
What is the significance of using a 50% duty cycle in the sampling process?
What is the significance of using a 50% duty cycle in the sampling process?
What is an expected outcome when displaying the SAMPLE/HOLD OUTPUT on an oscilloscope?
What is an expected outcome when displaying the SAMPLE/HOLD OUTPUT on an oscilloscope?
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Study Notes
ANACOM 1/1 Module Setup and Operation
- Connect the ANACOM 1/1 module to the power supply properly.
- Set the following initial board conditions:
- AUDIO INPUT SELECT switch to INT
- MODE switch to SSB
- OUTPUT AMPLIFIER’s GAIN preset fully clockwise
- SPEAKER switch in OFF position.
- Power on the ANACOM 1/1 board.
- Adjust the AUDIO OSCILLATOR block’s AMPLITUDE preset to maximum, and verify output sine wave frequency using an oscilloscope (300Hz to 3.4KHz).
- Set the BALANCE preset in BALANCE MODULATOR & BANDPASS FILTER CIRCUIT 1 fully clockwise.
- Monitor output from BALANCE MODULATOR & BANDPASS FILTER CIRCUIT 1 and 2 at specified test points.
- Observe DSBSC output entering the CERAMIC BANDPASS FILTER, focusing on upper sideband transmission only.
Monitoring and Signal Examination
- Verify the output of the CERAMIC BANDPASS FILTER using an oscilloscope; check for clean sine wave.
- Note any amplitude variation in filter output due to frequency response changes.
- Ensure all other initial conditions are met for further operations, including proper settings for TX OUTPUT SELECT and AUDIO AMPLIFIER’s VOLUME.
- Check the Transmitter’s output signal (t.p. 13) for good SSB waveform consistency across AUDIO OSCILLATOR’s FREQUENCY preset adjustments.
- Confirm zero amplitude output when the AMPLITUDE preset is fully counter-clockwise.
Transmitter-Receiver Communication
- Test SSB signal transmission to ANACOM 1/2 Receiver and verify through antenna loading effects.
- On receiver module, adjust settings to maximize I.F. AMPLIFIER 2 block output.
Frequency Modulation and Demodulation with Foster-Seeley Detector
- Connect a signal generator (1V p-p, 400 kHz) to the Foster-Seeley Detector block.
- Vary signal frequency from 430 kHz to 480 kHz, recording DC voltage at t.p.52 in 5 kHz steps for a frequency-voltage curve.
- Adjust CARRIER FREQUENCY preset to 450 kHz, modulate the signal from AUDIO OSCILLATOR, and apply it to the Foster-Seeley block.
- Monitor combined signals to identify sine wave and high-frequency ripple components.
- Use LOW PASS FILTER/AMPLIFIER to remove ripple and observe the filtered output.
Noise Impact on System
- Introduce noise (100 mV p-p, 2 kHz) to observe effects on FM output.
- Monitor input audio and LOW PASS FILTER output to evaluate ripple presence.
- Use SAMPLE/HOLD OUTPUT linked to FOURTH ORDER LOW PASS FILTER to analyze original waveform reconstruction.
Frequency and Duty Cycle Adjustments
- Vary sampling frequency and duty cycle to examine filter output amplitude consistency.
- Compare outputs from FIRST and SECOND ORDER LOW PASS FILTERS under varied sampling frequencies for distortion assessment.
MATLAB Simulink Experimentation
- Primary objective: Perform frequency modulation signal generation and detection using MATLAB Simulink.
- Adjust GAIN control on MODULATOR 2 to balance frequency components of DSK signal.
- Analyze the FSK signal and note variations during data changes (0 and 1).
- Remove unwanted carrier frequencies using low pass filtering and ensure output signal squaring with the correct pulse width adjustment.
System Functionality Verification
- Confirm synchronization across components and functionality of the FSK Transmitter-Receiver system.
- Allow testing of analog inputs and real-time reconstruction at modular outputs.
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