CA_BASIC
Basic - Safety
Safety follows the B-008 section of the Canadian question bank.
55
Questions
7
Sibling Topics
- Pool
- Basic
- Questions
- 55
- Topic
- Safety
- Region
- CA
Review by section order to build the topic framework first.
For regulatory and safety questions, prefer compliant and conservative actions.
For calculations, check units, multipliers, and approximations.
Topic Study Guide
This topic covers interference and safety issues in amateur radio operations, focusing on the causes and solutions for receiver overload, intermodulation, audio rectification, harmonics, and spurious emissions.
High-Yield Checks
- Receiver Overload & Desensitization: Strong nearby signals cause overload regardless of the band. Fix this by installing suitable filters at the receiver.
- Audio Rectification: RF entering audio equipment causes humming or clicking. Mitigate this by wrapping cables around a ferrite core.
- Harmonics vs. Parasitic Oscillations: Harmonics are exact multiples of the fundamental frequency, whereas parasitic oscillations occur above or below it.
- Out-of-band Emissions & Flat-topping: Flat-topping and splatter in SSB transmitters are typically caused by excessive microphone gain or overmodulation.
Trap Patterns
- Assuming interference is always the transmitter's fault. A perfectly clean strong signal can still overload a nearby receiver's front end.
- Confusing local and distant key clicks. Local clicks are from key contact sparking, while distant wideband clicks are due to poor waveform shaping.
- Mixing up intermodulation and harmonics. Intermodulation is the mixing of signals in a non-linear device, while harmonics are multiples of a single fundamental frequency.
Review Steps
- Categorize interference sources: distinguish between transmitter issues (harmonics, parasitic oscillations, overmodulation) and receiver issues (overload, audio rectification).
- Master audio rectification troubleshooting: remember that 'ferrite cores' and 'RFI filters' are the standard solutions for telephone or stereo interference.
- Familiarize yourself with key terms: accurately distinguish between Intermodulation, Desensitization, and Spurious emissions.
- Practice simple harmonic calculations: for example, the second harmonic of the 10-meter band (approx. 28 MHz) is 56 MHz, which helps in identifying interference sources.
Quick Checks
- What is the primary cause of flat-topping or splatter in an SSB transmitter?
- How do you resolve RF interference in a neighbor's telephone or stereo system?
- What is the difference in frequency behavior between harmonic emissions and parasitic oscillations?
- What is the phenomenon called when a receiver is deafened by a strong nearby signal on a different band?
Questions in This Topic
Choose Practice ModeB-008-001-001What is the cause of receiver overload?B-008-001-002What is one way to tell if your HF transmitter causes front-end overload interference to a neighbour's receiver?B-008-001-003If a neighbour reports television interference whenever you transmit, no matter what band you use, what is probably the cause of the interference?B-008-001-004What 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?B-008-001-005During 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?B-008-001-006The signals from two commercial transmitters combine outside your receiver to produce noise on a desired frequency. What type of interference is this?B-008-001-007You 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?B-008-001-008Two or more strong signals mix in your receiver to produce interference on a desired frequency. What is this called?B-008-001-009Two 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?B-008-001-010A 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?B-008-001-011You 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?B-008-002-001What devices would you install to reduce or eliminate interference to a home entertainment system from an HF transmitter?B-008-002-002What should be done if a properly operating amateur radio station is the cause of interference to a nearby telephone?B-008-002-003What sound is heard from a public address system if audio rectification of a nearby single-sideband transmission occurs?B-008-002-004What sound is heard from a public address system if audio rectification of a nearby CW transmission occurs?B-008-002-005If an amateur radio transmission is heard in a device that contains no RF components, what type of interference is this?B-008-002-006An amateur radio transmitter is being heard across the entire dial of a broadcast receiver. The receiver is most probably suffering from:B-008-002-007Your SSB HF transmissions are heard muffled on a sound system in the living room regardless of its volume setting. What causes this?B-008-002-008What device can be used to minimize the effect of RF pickup by audio wires connected to stereo speakers, intercom amplifiers, telephones, etc.?B-008-002-009Stereo speaker leads often act as antennas to pick up RF signals. What is one method you can use to minimize this effect?B-008-002-010One method of preventing RF from entering a stereo set through the speaker leads is to wrap each of the speaker leads:B-008-002-011You are using an HF off-centre-fed (OCF) unbalanced antenna. When you transmit on SSB, distorted audio and noise are heard from an outboard amplified speaker. What device could you install in the transmission line to mitigate this problem?B-008-003-001What term describes the undesired creation of new frequency components when one or more signals enter a non-linear device?B-008-003-002If someone tells you that signals from your hand-held transceiver are interfering with other signals on a frequency near yours, what could be the cause?B-008-003-003If your transmitter sends signals outside the band where it is transmitting, what is this called?B-008-003-004What problem may occur if your transmitter is operated without its cover or other shielding in place?B-008-003-005In Morse code transmission, local RF interference (key clicks) is produced by:B-008-003-006Key clicks, heard from a Morse code transmitter at a distant receiver, are the result of:B-008-003-007In a Morse code transmission, broad bandwidth RF interference (key clicks) heard at a distance is produced by:B-008-003-008What should you do if you learn your transmitter is producing key clicks?B-008-003-009What term describes an unwanted oscillation in an amplifier or oscillator circuit?B-008-003-010What can cause parasitic oscillations in a stage?B-008-003-011Transmitter RF amplifiers can generate parasitic oscillations:B-008-004-001If a neighbour reports television interference on one or two channels only when you transmit on 15 metres, what is probably the cause of the interference?B-008-004-002What are harmonic emissions?B-008-004-003Why are harmonic emissions from an amateur radio station not wanted?B-008-004-004What term describes unwanted radio energy transmitted just outside the necessary bandwidth?B-008-004-005If you are told your station was heard on 21.375 MHz but at the time you were operating on 7.125 MHz. What is one reason that could cause this to happen?B-008-004-006What causes splatter interference?B-008-004-007A television tuned to channel 3 (60 MHz - 66 MHz) experiences interference when you are transmitting on the 15-metre band. Other channels are not affected. What is the most likely cause?B-008-004-008What is the probable cause of "flat topping" (non-linear operation) of an amplifier in an SSB transmitter?B-008-004-009Which of the following may cause excessive harmonics in a transmitter?B-008-004-010An interfering signal from an HF transmitter is found to have a frequency of 56 MHz. What could be the source?B-008-004-011Harmonics may be produced in the RF power amplifier of a transmitter if:B-008-005-001What is the frequency response of an ideal notch filter?B-008-005-002A filter attenuates frequencies below its cut-off frequency of 60 MHz. What type of filter is it?B-008-005-003What type of filter attenuates RF energy above and below a certain range of frequencies?B-008-005-004Why should the impedance of a filter match the transmission line where it is inserted?B-008-005-005Listening to shortwave on a low-cost software defined receiver (SDR), you hear several stations known to operate on much higher frequencies. What type of filter could help?B-008-005-006You need to install an AC line filter to reduce radio frequency noise heard in your station equipment. What type of frequency response should it have?B-008-005-007A strong interfering signal is very close to your receive frequency. Which type of filter can effectively suppress it?B-008-005-008In a Field Day operation with separate transmitters assigned to specific bands, what type of filter is needed on the receivers to minimize interference?B-008-005-009A nearby high-power HF broadcast station in the 31-metre band is interfering with your reception on the 40-metre and 30-metre bands. What type of filter is needed on the receiver to minimize interference?B-008-005-010Your 2-metre station suffers receiver overload from several land mobile service transmitters on adjacent bands. What type of filter could help?B-008-005-011A filter attenuates frequencies above its cut-off frequency of 40 MHz. What type of filter is it?