B-008 — Interference and suppression

When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.

All 55 questions

• B-008-001-001 What is the cause of receiver overload?
• B-008-001-002 What is one way to tell if your HF transmitter causes front-end overload interference to a neighbour's receiver?
• B-008-001-003 If a neighbour reports television interference whenever you transmit, no matter what band you use, what is probably the cause of the interference?
• B-008-001-004 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?
• B-008-001-005 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?
• B-008-001-006 The signals from two commercial transmitters combine outside your receiver to produce noise on a desired frequency. What type of interference is this?
• B-008-001-007 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?
• B-008-001-008 Two or more strong signals mix in your receiver to produce interference on a desired frequency. What is this called?
• B-008-001-009 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?
• B-008-001-010 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?
• B-008-001-011 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?
• B-008-002-001 What devices would you install to reduce or eliminate interference to a home entertainment system from an HF transmitter?
• B-008-002-002 What should be done if a properly operating amateur radio station is the cause of interference to a nearby telephone?
• B-008-002-003 What sound is heard from a public address system if audio rectification of a nearby single-sideband transmission occurs?
• B-008-002-004 What sound is heard from a public address system if audio rectification of a nearby CW transmission occurs?
• B-008-002-005 If an amateur radio transmission is heard in a device that contains no RF components, what type of interference is this?
• B-008-002-006 An amateur radio transmitter is being heard across the entire dial of a broadcast receiver. The receiver is most probably suffering from:
• B-008-002-007 Your SSB HF transmissions are heard muffled on a sound system in the living room regardless of its volume setting. What causes this?
• B-008-002-008 What device can be used to minimize the effect of RF pickup by audio wires connected to stereo speakers, intercom amplifiers, telephones, etc.?
• B-008-002-009 Stereo speaker leads often act as antennas to pick up RF signals. What is one method you can use to minimize this effect?
• B-008-002-010 One method of preventing RF from entering a stereo set through the speaker leads is to wrap each of the speaker leads:
• B-008-002-011 Stereo amplifiers often have long leads that pick up transmitted signals because they act as:
• B-008-003-001 What term describes the undesired creation of new frequency components when one or more signals enter a non-linear device?
• B-008-003-002 If 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-008-003-003 If your transmitter sends signals outside the band where it is transmitting, what is this called?
• B-008-003-004 What problem may occur if your transmitter is operated without its cover or other shielding in place?
• B-008-003-005 In Morse code transmission, local RF interference (key clicks) is produced by:
• B-008-003-006 Key clicks, heard from a Morse code transmitter at a distant receiver, are the result of:
• B-008-003-007 In a Morse code transmission, broad bandwidth RF interference (key clicks) heard at a distance is produced by:
• B-008-003-008 What should you do if you learn your transmitter is producing key clicks?
• B-008-003-009 What term describes an unwanted oscillation in an amplifier or oscillator circuit?
• B-008-003-010 What can cause parasitic oscillations in a stage?
• B-008-003-011 Transmitter RF amplifiers can generate parasitic oscillations:
• B-008-004-001 If 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-008-004-002 What are harmonic emissions?
• B-008-004-003 Why are harmonic emissions from an amateur radio station not wanted?
• B-008-004-004 What term describes unwanted radio energy transmitted just outside the necessary bandwidth?
• B-008-004-005 If 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-008-004-006 What causes splatter interference?
• B-008-004-007 A 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-008-004-008 What is the probable cause of "flat topping" (non-linear operation) of an amplifier in an SSB transmitter?
• B-008-004-009 Which of the following may cause excessive harmonics in a transmitter?
• B-008-004-010 An interfering signal from an HF transmitter is found to have a frequency of 56 MHz. What could be the source?
• B-008-004-011 Harmonics may be produced in the RF power amplifier of a transmitter if:
• B-008-005-001 What is the frequency response of an ideal notch filter?
• B-008-005-002 A filter attenuates frequencies below its cut-off frequency of 60 MHz. What type of filter is it?
• B-008-005-003 What type of filter attenuates RF energy above and below a certain range of frequencies?
• B-008-005-004 Why should the impedance of a filter match the transmission line where it is inserted?
• B-008-005-005 Listening 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-008-005-006 You 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-008-005-007 A strong interfering signal is very close to your receive frequency. Which type of filter can effectively suppress it?
• B-008-005-008 In a Field Day operation with separate transmitters assigned to specific bands, what type of filter is needed on the receivers to minimize interference?
• B-008-005-009 A 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-008-005-010 Your 2-metre station suffers receiver overload from several land mobile service transmitters on adjacent bands. What type of filter could help?
• B-008-005-011 A filter attenuates frequencies above its cut-off frequency of 40 MHz. What type of filter is it?