key words: INPUT to SPEECH AMPLIFIER. The Speech Amplifier serves to bring up the feeble microphone signal to a working level. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
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The Speech Amplifier serves to bring up the feeble microphone signal to a working level. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: FM TANSMITTER. Frequency Modulation depends on frequency deviation to carry the message. The obvious way to effect deviation is to use modulation to alter the Oscillator frequency. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
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The Oscillator frequency and the deviation impressed on it by the Modulator are brought up to the operating frequency through multiplication. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
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The Oscillator frequency and the deviation impressed on it by the Modulator are brought up to the operating frequency through multiplication. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In all transmitters, the last stage before the Antenna is a Power Amplifier which imparts the transmitted signal its actual power. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In all transmitters, the last stage before the Antenna is a Power Amplifier which imparts the transmitted signal its actual power. The FM Transmitter block diagram: Microphone, Speech Amplifier, Modulator, Oscillator, Frequency Multiplier, Power Amplifier, Antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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To achieve stability (absence of frequency 'drift'), Master Oscillators are always low-power stages. Amplification must follow; that's the purpose of the Driver/Buffer. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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ALL transmitters require a Power Supply, the primary source of Direct Current (DC), required by active devices such as transistors and vacuum tubes. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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To achieve stability, Master Oscillators are always low-level stages. Amplification must follow; that's the purpose of the Driver/Buffer. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Telegraphy is equivalent to 'on-off keying' ( an 'interrupted carrier'). The Telegraph Key allows the operator to send bursts of RF energy to the antenna per the rhythm of his hand movement on the key. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In all transmitters, the last stage before the Antenna is a Power Amplifier which imparts the transmitted signal its actual power. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In all transmitters, the last stage before the Antenna is a Power Amplifier which imparts the transmitted signal its actual power. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna. A Power Supply supplies DC to all stages. A Telegraph Key activates the Driver and Power Amplifier when pressed.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator receives two inputs: RF Oscillator, Speech Amplifier. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator produces a double-sideband suppressed-carrier signal. The Filter keeps one sideband. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator produces a double-sideband suppressed-carrier signal. The Filter keeps one sideband. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Speech Amplifier serves to bring up the feeble microphone signal to a working level. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator receives two inputs: RF Oscillator, Speech Amplifier. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Mixer takes in the SSB signal and the VFO output to bring up the SSB signal at the operating frequency. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Mixer takes in the SSB signal and the VFO output to bring up the SSB signal at the operating frequency. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In SSB, the Power Amplifier must be linear because it amplifies an amplitude modulated signal. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In SSB, the Power Amplifier must be linear because it amplifies an amplitude modulated signal. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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"Chirp": Inadequate voltage regulation causes the Master Oscillator frequency to shift when the Telegraph Key is pressed. Perceived at the receive location as a change of pitch during each Morse element. Frequency 'drift' is a lack of stability in the Master Oscillator.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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"Chirp": Inadequate voltage regulation causes the Master Oscillator frequency to shift when the Telegraph Key is pressed. Perceived at the receive location as a change of pitch during each Morse element. Current varies as demand varies in a transmitter. A Low-Pass filter reduces 'harmonics'.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: VFO, Variable Frequency Oscillator. The CW Transmitter block diagram: Master Oscillator, Driver/Buffer, Power Amplifier, Antenna.
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key word: AMPLITUDE. The instantaneous voltage of an AC waveform. AM (Amplitude Modulation) impresses the message onto the RF carrier by varying its amplitude.
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key word: AMPLITUDE. The instantaneous voltage of an AC waveform. AM (Amplitude Modulation) impresses the message onto the RF carrier by varying its amplitude.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Telegraphy is equivalent to 'on-off keying' (an 'interrupted carrier'). The Telegraph Key allows the operator to send bursts of RF energy to the antenna per the rhythm of his hand movement on the key. Key-Clicks is a type of interference where a CW signal generates unwanted sidebands.
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The 'Final' = the Power Amplifier. A serious impedance mismatch in the antenna system forces the Power Amplifier to operate in a load for which it was not designed. A significant mismatch causes high SWR (Standing Wave Ratio) which leads to voltage and current peaks which could damage the Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Impedance Match: maximum power transfer occurs when the impedance of the load matches the internal impedance of the source. A "slight mismatch" leads to reduced power being delivered to the antenna.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: STABLE. Absence of frequency "drift". A good oscillator remains on frequency despite mechanical vibrations, voltage or temperature variations.
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Power Amplifiers have a certain 'efficiency', the ratio of DC power required to obtain an RF output. The difference goes up in heat. This is the reason for the 'heat sinks' on the back of transmitters.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Power Amplifiers have a certain 'efficiency', the ratio of DC power required to obtain an RF output. The difference goes up in heat. This is the reason for the 'heat sinks' on the back of transmitters.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: MICROPHONE GAIN SET TOO HIGH. This leads to 'overmodulation' evidenced by distorted speech plus using excessive bandwidth on the air (splatter) which interferes with stations using adjacent frequencies ('out-of-channel emissions').
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key words: TOO MUCH SPEECH PROCESSING. 'Speech processing' is raising the average amplitude of the audio input from the microphone closer to an acceptable peak value: i.e., make every passage of the spoken words equally loud. Too much speech processing leads to distortion and possibly driving the Linear Power Amplifier with too large a signal (overdriving). This leads to 'overmodulation' evidenced by distorted speech plus occupying excessive bandwidth on the air (splatter) which interferes with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: ENVELOPE. PEP -- Peak Envelope Power ( a specification for SSB transmitters ): the average power at the output of a transmitter during one cycle at a modulation peak.
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By transposing the voice signal into the radio spectrum, the SSB transmitter manages to only use the approximate bandwidth of the original modulation ( speech frequencies important for communications span 300 hertz to 3000 hertz, a bandwidth of 2700 hertz ). SSB uses half the bandwidth of AM.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator produces a double-sideband suppressed-carrier signal. The Filter keeps one sideband. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Plain AM (Amplitude Modulation) produces a radio Carrier, an upper sideband and a lower sideband. The sidebands are the ever-changing sum and differences of the modulating frequency (follows voice) and the carrier frequency (set at the operating frequency). The carrier by itself does NOT convey information. The message is in the sidebands. Suppressing the carrier permits using the full capacity of the Power Amplifier for the sidebands. Note: Suppressing the carrier an one sideband yields Single Sideband.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: OVERMODULATED. 'Overmodulation' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
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ALC -- Automatic Level Control: a feedback circuit from the Linear Power Amplifier to an earlier amplifier stage which seeks to avoid overdriving the transmitter with too much audio. When the ALC acts, it is a corrective action. An infrequent ALC action on modulation peaks indicates that there is no overdriving. If the ALC needed to intervene constantly, this would indicate that the operator is trying to feed too much audio through the transmitter.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The Balanced Modulator produces a double-sideband suppressed-carrier signal. The Filter keeps one sideband. The SSB Transmitter block diagram: The Balanced Modulator takes in two signals: fixed frequency from an RF Oscillator and the microphone signal after it has passed through a Speech Amplifier. Out of the Balanced Modulator, a Filter selects the desired sideband. This SSB signal is mixed with a Variable Frequency Oscillator (VFO) signal by a Mixer. Out of the Mixer, the SSB signal is now at the operating frequency and is taken through a LINEAR Power Amplifier.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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In Amplitude Modulation, the position, along the radio spectrum, of a 'side frequency' within a sideband is the sum (or difference) of the modulating frequency and carrier frequency. The statement is also true with Single Sideband (SSB) where the carrier has been suppressed: the position of a 'side frequency' only has meaning in relation with the position of the phantom carrier. Suitable demodulation at the receiving end supposes that the "carrier is re-inserted" so that each side frequency (a great number of which form a sideband) can be rendered as an exact audio frequency.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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ALC -- Automatic Level Control: a feedback circuit from the Linear Power Amplifier to an earlier amplifier stage which seeks to avoid overdriving the transmitter with too much audio. When the ALC acts, it is a corrective action. An infrequent ALC action on modulation peaks indicates that there is no overdriving. If the ALC needed to intervene constantly, this would indicate that the operator is trying to feed too much audio through the transmitter.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key words: MICROPHONE GAIN, DEVIATION TOO HIGH. 'Overdeviation (FM)' or 'Overmodulation (AM, SSB)' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: SHOUT. 'Overdeviation (FM)' or 'Overmodulation (AM, SSB)' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: OVERDEVIATION. 'Overdeviation (FM)' or 'Overmodulation (AM, SSB)' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The concept here is that IF NO AUDIO is fed in an FM transmitter, the carrier put out at the Power Amplifier has full amplitude anyway. A carrier which conveys no message is an 'unmodulated carrier'.
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FM -- Frequency Modulation. As the process removes much of the ambient electrical noise, weak signals can be rendered with better 'signal plus noise' to 'noise' ratio. However, this comes at a price of more occupied bandwidth, 10 to 20 kilohertz in usual amateur communications.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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'Overdeviation (FM)' or 'Overmodulation (AM, SSB)' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Direct FM: Use a variable reactance element as one of the elements of an oscillator to cause frequency deviation. Indirect FM: apply the modulating voltage to a variable reactance element connected to a tuned circuit later in the transmit chain, where it will produce phase modulation rather than frequency modulation.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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The usual bandwidth of FM with 5 kHz deviation on amateur bands is between 10 to 20 kilohertz. On the 10 metre band (28.0 to 29.7 MHz), maximum permitted bandwidth is 20 kHz. "Radiotelephone signals in a frequency band below 29.50 MHz cannot be automatically retransmitted unless these signals are received from a station operated by a person qualified to transmit on frequencies below 29.50 MHz (RBR-4, formerly RIC-2)."
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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key word: DISTORTION. 'Overdeviation (FM)' or 'Overmodulation (AM, SSB)' results in distorted speech plus using excessive bandwidth on the air (splatter) and interfering with stations using adjacent frequencies ('out-of-channel emissions').
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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