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Questions and Answers
What does the designation 'A8F' represent in the context of ITU emissions?
What does the designation 'A8F' represent in the context of ITU emissions?
What does the 'G' in the designation 'G7W' signify?
What does the 'G' in the designation 'G7W' signify?
Which type of information is transmitted using the designation 'G7W'?
Which type of information is transmitted using the designation 'G7W'?
In the ITU emissions designation '3k24', what does '3.24 kHz' indicate?
In the ITU emissions designation '3k24', what does '3.24 kHz' indicate?
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How many channels are specified in the designation '3k24'?
How many channels are specified in the designation '3k24'?
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What does the letter 'A' represent in the AM voice signal code A3?
What does the letter 'A' represent in the AM voice signal code A3?
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Which code designation indicates a DSB two sidebands suppressed carrier telephony?
Which code designation indicates a DSB two sidebands suppressed carrier telephony?
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What does '3' represent in the code A3?
What does '3' represent in the code A3?
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In the ITU emission designation system, what is the purpose of the codes?
In the ITU emission designation system, what is the purpose of the codes?
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Which of the following represents a SSB vestigial single sideband with a 30% pilot carrier?
Which of the following represents a SSB vestigial single sideband with a 30% pilot carrier?
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What is selectivity in a communication receiver?
What is selectivity in a communication receiver?
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How is selectivity achieved in a receiver?
How is selectivity achieved in a receiver?
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What happens if the bandwidth of a tuned circuit becomes too narrow?
What happens if the bandwidth of a tuned circuit becomes too narrow?
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What does the quality factor (Q) in a tuned circuit influence?
What does the quality factor (Q) in a tuned circuit influence?
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What is the formula for the bandwidth (BW) of a tuned circuit?
What is the formula for the bandwidth (BW) of a tuned circuit?
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What is the role of sensitivity in communication receivers?
What is the role of sensitivity in communication receivers?
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What could happen if a radio receiver is too sensitive?
What could happen if a radio receiver is too sensitive?
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The ideal bandwidth of a selectivity curve in a receiver should be:
The ideal bandwidth of a selectivity curve in a receiver should be:
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What does MDS stand for in relation to signal level?
What does MDS stand for in relation to signal level?
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In what unit is MDS expressed?
In what unit is MDS expressed?
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What does the formula $P_{dBm} = 10 \log_{10} \frac{P}{1 mW}$ calculate?
What does the formula $P_{dBm} = 10 \log_{10} \frac{P}{1 mW}$ calculate?
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If a signal with 1 µV produces a power across 50 Ω, what is the power in watts?
If a signal with 1 µV produces a power across 50 Ω, what is the power in watts?
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How is power expressed in dB for $2 \times 10^{-14} W$?
How is power expressed in dB for $2 \times 10^{-14} W$?
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What is the first part of the radio emission code designation?
What is the first part of the radio emission code designation?
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What do the numbers in the radio emission code designation signify?
What do the numbers in the radio emission code designation signify?
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What is the significance of lower subscript letters in radio emission codes?
What is the significance of lower subscript letters in radio emission codes?
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What is the purpose of cascading circuits or using filters in electronic communication systems?
What is the purpose of cascading circuits or using filters in electronic communication systems?
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How is the shape factor expressed in the context of receiver bandwidth?
How is the shape factor expressed in the context of receiver bandwidth?
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What happens to the shape factor as the skirts of a tuned circuit response curve become steeper?
What happens to the shape factor as the skirts of a tuned circuit response curve become steeper?
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Which of the following represents how sensitivity in a receiver is mainly described?
Which of the following represents how sensitivity in a receiver is mainly described?
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If a receiver has a shape factor of 2.25, what can be inferred about its skirt selectivity?
If a receiver has a shape factor of 2.25, what can be inferred about its skirt selectivity?
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What is the relationship between gain and sensitivity in a receiver?
What is the relationship between gain and sensitivity in a receiver?
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What does a shape factor of 1 signify in terms of selectivity?
What does a shape factor of 1 signify in terms of selectivity?
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Which factor primarily influences the ability of a receiver to discern weak signals?
Which factor primarily influences the ability of a receiver to discern weak signals?
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What does the first part of the code 'BBBB' represent?
What does the first part of the code 'BBBB' represent?
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Which letter represents Frequency Modulation in the modulation type classification?
Which letter represents Frequency Modulation in the modulation type classification?
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In the bandwidth designator list, what does 'M' stand for?
In the bandwidth designator list, what does 'M' stand for?
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Which of the following modulation types indicates a combination of Amplitude Modulation and Frequency Modulation?
Which of the following modulation types indicates a combination of Amplitude Modulation and Frequency Modulation?
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What does the digit '3' indicate in terms of modulating signal type?
What does the digit '3' indicate in terms of modulating signal type?
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Which information type is indicated by the letter 'E'?
Which information type is indicated by the letter 'E'?
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What does the letter 'N' signify in the modulation types?
What does the letter 'N' signify in the modulation types?
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Which of the following indicates no modulation in modulating signal types?
Which of the following indicates no modulation in modulating signal types?
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If a signal is classified as '2M25', what frequency does it represent?
If a signal is classified as '2M25', what frequency does it represent?
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What does the letter 'W' represent in modulation types?
What does the letter 'W' represent in modulation types?
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Study Notes
Communication Receivers
- Transmitted signals weaken over long distances, picking up noise.
- Receivers need selectivity and sensitivity to recover the original signal.
- Selectivity is the ability to identify and select a desired signal from others.
- Sensitivity is the ability to pick up weak signals and amplify them.
Selectivity
- Achieved using tuned circuits (LC-tuned circuits).
- LC-tuned circuits consist of an inductor and a capacitor.
- Selectivity is controlled by the quality factor (Q) of the LC-tuned circuit.
- Ideal bandwidth (BW) must be wide enough to pass the signal and its sidebands, but narrow enough to eliminate adjacent frequencies.
- Bandwidth formula: BW = fr / Q
- Increasing Q narrows the bandwidth, improving attenuation of unwanted signals.
- However, too narrow a bandwidth can attenuate the signal's sidebands, causing information loss.
Sensitivity
- Sensitivity is mainly determined by overall gain. Higher gain leads to better sensitivity.
- Signal-to-noise ratio (SNR) also affects sensitivity. Higher SNR (signal compared to noise) improves sensitivity.
Minimum Discernible Signal (MDS)
- MDS is a method for expressing receiver sensitivity.
- It is the input signal level almost equal to the average noise floor of the receiver.
- MDS is expressed in dBm (decibels relative to one milliwatt).
- Formula: dBm = 10 log10 (P/1mW), where P is power in watts
Classification of Radio Emissions
- Radio emission codes are used to identify types of signals.
- The codes consist of a capital letter (modulation type), a number (information type), and lowercase letters (subscript details).
- Examples include AM (amplitude modulation) and specific information types like voice or data.
ITU Emission Designations
- A system for describing signals (more variations than previous system)
- Used to easily describe format and modulation for radio transmissions
- Format BBBB 123 45,
- BBBB is the bandwidth.
- First digit is the modulation type
- Second digit is the modulation type (e.g., voice/data)
- Third digit is the signal type (e.g., analog/digital)
- Optional (possibly 4th or 5th digit) additional specifics about the signal.
- Bandwidth measurements are often expressed with units like kHz, MHz, etc.
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Description
Test your knowledge on communication receivers, focusing on their selectivity and sensitivity. This quiz covers key concepts such as LC-tuned circuits, the quality factor, and bandwidth calculations, essential for understanding signal transmission and reception.
