B-008
Subelement B-008
Section B-008-001
Section B-008-001
What is the cause of receiver overload?
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Frequency instability of a transmitter
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Overmodulation of a transmitter
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Parasitic oscillations in a transmitter
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Correct AnswerVery strong signal from a transmitter
'Receiver Overload', also known as 'Front-End Overload' or 'RF Overload', is a problem where the early stages of a receiver (i.e., RF amplifier or mixer) are overwhelmed by a strong nearby transmitter. For example, TV reception is affected by an HF transmitter. In the case of 'overload', the exact transmit frequency does not seem to matter: the effect is the same for a broad range of transmit frequencies. This contrasts with 'harmonics' where a multiple of a given transmit frequency is the cause of the interference.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What is one way to tell if your HF transmitter causes front-end overload interference to a neighbour's receiver?
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Interference is heard regardless of the volume setting on the receiver
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Adding receiver shielding has no effect
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Adding a low-pass filter at the transmitter solves the problem
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Correct AnswerTransmitting on various frequencies produces similar interference
'Receiver Overload', also known as 'Front-End Overload' or 'RF Overload', is a problem where the early stages of a receiver (i.e., RF amplifier or mixer) are overwhelmed by a strong nearby transmitter. For example, TV reception is affected by an HF transmitter. In the case of 'overload', the exact transmit frequency does not seem to matter: the effect is the same for a broad range of transmit frequencies. This contrasts with 'harmonics' where a multiple of a given transmit frequency is the cause of the interference.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
If a neighbour reports television interference whenever you transmit, no matter what band you use, what is probably the cause of the interference?
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Correct AnswerReceiver overload
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Deficient harmonic suppression
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Incorrect antenna length
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Spurious emissions
'Receiver Overload', also known as 'Front-End Overload' or 'RF Overload', is a problem where the early stages of a receiver (i.e., RF amplifier or mixer) are overwhelmed by a strong nearby transmitter. For example, TV reception is affected by an HF transmitter. In the case of 'overload', the exact transmit frequency does not seem to matter: the effect is the same for a broad range of transmit frequencies. This contrasts with 'harmonics' where a multiple of a given transmit frequency is the cause of the interference.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What type of filter should be connected to a TV receiver as the first step in trying to prevent receiver overload from an amateur radio HF transmission?
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Band-pass
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AC line filter
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Correct AnswerHigh-pass
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Low-pass
Key words: TV, OVERLOAD, HF. TV Channels begin at 54 MHz; the HF range ends at 30 MHz. To prevent overload to a TV receiver from an HF transmitter, a HIGH-PASS filter can be installed on the TV receiver to allow higher frequencies through while attenuating lower frequencies. The object of the filtering being to keep the HF signals out of the TV receiver.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
During a club Field Day outing, reception on the 20-metre SSB station is compromised every time the 20-metre CW station is on the air. What might cause such interference?
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Improper station grounding
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Harmonic emission
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Both stations are fed from the same generator
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Correct AnswerReceiver desensitization
The proximity of a transmitter a short distance from a receiver, especially on the same band, may cause receiver overload. Symptoms can be loss of receiver sensitivity (desensitization) or weird noises.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
The signals from two commercial transmitters combine outside your receiver to produce noise on a desired frequency. What type of interference is this?
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Receiver overload
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Spurious emissions
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Correct AnswerIntermodulation
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Harmonic emissions
Intermodulation is the undesired mixing of two or more signals that creates new signals (products) at frequencies other than the original signals. The mixing may happen in the affected equipment or elsewhere around it.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
You have connected your hand-held VHF transceiver to an outside gain antenna. You now hear a mixture of signals together with different modulation on your desired frequency. What is the nature of this interference?
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Correct AnswerReceiver intermodulation
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Harmonics from other stations
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Audio stage overload
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Audio stage intermodulation
"Intermod" for short, a plague in urban environments. High-power transmitters used for commercial purposes multiply the possibilities that two or more signals mix and produce a result (product) which OVERLOADS your receiver. The actual mixing may occur in your receiver, in which case filtering might be helpful, or elsewhere altogether. The results: loss of sensitivity, noises and squeals covering the intended signal in your receiver.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
Two or more strong signals mix in your receiver to produce interference on a desired frequency. What is this called?
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Front-end desensitization
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Harmonic interference
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Capture effect
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Correct AnswerIntermodulation interference
"Intermod" for short, a plague in urban environments. High-power transmitters used for commercial purposes multiply the possibilities that two or more signals mix and produce a result (product) which OVERLOADS your receiver. The actual mixing may occur in your receiver, in which case filtering might be helpful, or elsewhere altogether. The results: loss of sensitivity, noises and squeals covering the intended signal in your receiver.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
Two mobile stations are communicating through a repeater. As they arrive in close proximity to each other, they begin to have difficulty communicating. What is the most likely cause?
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CTCSS tones are activating the receivers' squelch circuits
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Correct AnswerTransmitter signals are desensitizing the receivers
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Transmitter signals are mixing with the repeater signal to cause intermodulation
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They have entered a null area of their antenna patterns
The proximity of a transmitter a short distance from a receiver, especially on the same band, may cause receiver overload. Symptoms can be loss of receiver sensitivity (desensitization) or weird noises.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
A television receiver suffers interference on channel 5 (76 MHz - 82 MHz) only when you transmit on 14 MHz. From your home you see the tower of a commercial FM station known to broadcast on 92.5 MHz. Which of these solutions would you try first?
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Insert a low-pass filter at the HF transmitter
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Insert a low-pass filter at the television receiver
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Correct AnswerInsert a high-pass filter at the television receiver
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Insert a high-pass filter at the HF transmitter
Intermodulation is a special case of overload. In this example, the mixing of a carrier at 92 MHz mixes with your signal at 14 MHz creates a new intermodulation product at 78 MHz. Given the proximity of the FM transmitter, the mixing may happen in the TV receiver. TV Channels begin at 54 MHz; the HF range ends at 30 MHz. To prevent overload to a TV receiver from an HF transmitter, a HIGH-PASS filter can be installed on the TV receiver to allow higher frequencies through while attenuating lower frequencies. The object of the filtering being to keep the HF signals out of the TV receiver.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
You are experiencing interference in your VHF receiver. You have determined that signals from two nearby transmitters are mixing in your receiver to cause the interference. What device can you install to reduce the interference?
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Narrow band IF filter
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Common-mode choke
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Correct AnswerSuitable filter at the receiver
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RF attenuator
Intermodulation is a special case of overload. In this example, the mixing occurs in your receiver. You must reduce the overload by keeping the offending signals out of your receiver.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
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