Trystan Casey
Television interference (TVI) is a type of electromagnetic interference that affects television reception. This can be caused by a range of natural and man-made phenomena, such as lightning, solar flares, and electrical equipment. An example of TVI is impulse noise, which is a fast and almost instantaneous type of electromagnetic interference caused by sources such as vehicle ignitions, electrical equipment, and sparks on cookers. Another example is TV pickup, which refers to the surge in demand for electricity during commercial breaks of popular TV programmes when viewers switch on their electric kettles. This sudden increase in demand can cause a drop in mains frequency across the electrical grid.
| Characteristics | Values |
|---|---|
| Definition | A brief burst of electromagnetic energy |
| Other names | Transient electromagnetic disturbance (TED), electromagnetic pulse (EMP) |
| Origin | Natural or artificial |
| Occurrence | As an electromagnetic field, as an electric field, as a magnetic field, or as a conducted electric current |
| Effects | Disrupt communications, damage electronic equipment, cause physical damage to objects |
| Examples | Lightning strike, solar storm |
| Management | A branch of electromagnetic compatibility (EMC) engineering |
| Prediction | The National Grid Energy Balancing Team uses a computer program to predict demand |
| Preparation | Fast reserves, balance mechanism units, pumped storage reservoirs, fossil fuel stations, nuclear power stations |
| Interference sources | Nearby electrical equipment, telecoms masts, vehicle ignitions, electrical equipment, lights, computers, phone chargers, lighting systems |
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What You'll Learn
Impulse noise
There are various sources of impulse noise, including both natural and man-made phenomena. Natural sources include lightning, while man-made sources include sparks from ignition systems, electrical equipment, light switches, furnaces, and dishwashers. In addition, certain types of electrical appliances can emit high levels of impulse noise, causing electrical interference in nearby devices. For example, an old television was found to be the cause of broadband outages in a village in Wales, UK, when it was switched on every morning at 7 am, emitting a single high-level impulse noise (SHINE).
To mitigate the impact of impulse noise, it is advisable to maintain a distance between TV equipment and potential sources of interference. If the source of interference is nearby, it may be possible to identify it by cutting off the power to individual items and observing if the TV reception improves. In some cases, more specialised equipment, such as a spectrum analyser, may be required to pinpoint the exact source of the impulse noise.
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Interference from electrical equipment
- Computers and other digital electronic devices: These devices contain rapidly switching circuits that create and use signals switched on and off at high speed, which can cause interference.
- Switched-mode power supplies: These are found in consumer electronic products like phone chargers and lighting systems and can cause a bad TV picture.
- Nearby electrical equipment: Items such as fridges, freezers, fish tank heaters, and central heating systems can create sparks as they turn on or off, causing interference.
- Electric railways: These can be a strong source of interference, particularly for analog television broadcasts.
To identify the source of interference, try cutting off the power to each item near your TV and see if the reception improves. It is also recommended to maintain some distance between your TV equipment and potential sources of interference.
In addition to the above, a unique phenomenon called "TV pickup" occurs in the UK, where a surge in demand for electricity during commercial breaks of popular TV programs is caused by the near-simultaneous switching on of millions of high-powered electric kettles. This sudden increase in demand can cause a drop in mains frequency across the National Grid.
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TV pickups
A TV pickup is a surge in electricity demand that occurs during breaks in popular television programmes. This phenomenon is common in the UK, where individual programmes can attract a large audience share. The surge in demand is caused by the near-simultaneous switching on of high-power electric appliances, typically kettles, by millions of viewers during the breaks.
To prepare for TV pickups, the National Grid Energy Balancing Team runs a computer program that compares the current day with corresponding periods over the past five years to predict the size of the demand. They also study TV schedules to anticipate demand from popular shows. Grid employees must be familiar with popular soap opera storylines, as these can cause a sudden rise in demand.
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Sources of interference
There are many sources of interference that can cause issues with television signals. These can be natural or man-made phenomena that disrupt the reception of television signals. Impulse noise is a type of fast, almost instantaneous electromagnetic interference. Examples of impulse noise include interference from car and vehicle ignitions, electrical equipment, sparks on hobs/cookers, and lights.
Some common sources of interference include:
- Nearby electrical devices: Interference can be caused by a nearby electrical device emitting a strong signal or operating within the same frequency range as your TV. This can overload your TV's tuners or distribution equipment, resulting in poor reception.
- Household appliances: Everyday household appliances, such as microwaves, outdoor lights, CCTV cameras, and even older television sets, can emit electrical interference that disrupts television signals.
- Spark discharges: Natural and artificial spark discharges can cause interference. This includes sparks generated by static electricity, as well as sparks from malfunctioning electrical devices, electric railways, and ignition systems on cars and motorbikes.
- Computers and digital electronic equipment: These devices operate with rapidly switching circuits, creating and using signals that are switched on and off at high speeds. The harmonics in these signals can cause interference, particularly in the case of modern PCs operating in the VHF/UHF frequency range.
- LED lights: LED lights, especially when used as replacements for halogen lights with the original transformer, can cause interference with television signals. This is due to the lower power usage, which forces the LED lights to operate outside their normal parameters.
- Fluorescent lights and street lights: When these types of lights become faulty, they can cause problems with television reception, such as picture break-up or freezing.
- Thermostats: A faulty thermostat in your home or a neighbour's home can emit an electric spark that blocks the television signal for a short time.
To identify the source of interference, you can try unplugging electrical devices one at a time to see if the TV reception improves. Additionally, using a portable battery-powered AM radio tuned to a lower frequency can help locate the source, as you will hear static or buzzing as you get closer to the interference source.
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Electromagnetic interference
Television interference (TVI) is a type of electromagnetic interference (EMI) that affects television reception. Electromagnetic interference is defined as the "effect of unwanted energy" from an external source, which disrupts the use of your television. This can include radio frequency signals, which may prevent reception altogether, cause a temporary loss of signal, or affect the quality of the sound or picture produced.
EMI can be classified as either narrowband or broadband, depending on the spread of the frequency range. Sources of EMI include power supply units, transmission lines, substations, audio power amplifiers, and loudspeakers. Radio Frequency Interference (RFI) is a type of EMI that can be caused by amateur radios, CBs, and radio and television stations. Impulse noise is a type of fast, almost instantaneous EMI, which includes interference from vehicle ignitions, electrical equipment, sparks on cookers, and lights.
There are various ways to identify and fix the source of EMI. One method is to cut off the power to each item near your TV equipment and see if the reception improves. Another way is to unplug household electrical devices one at a time to determine whether the interference is caused by a transmitter or electrical equipment. Design flaws, such as insufficient shielding or frayed wires, can also make equipment more susceptible to EMI.
To prevent EMI, many countries have implemented regulations and standards for products to meet certain levels of electromagnetic compatibility (EMC). These regulations aim to reduce the immunity and emission levels of electromagnetic interference from digital equipment. By adhering to these standards, products can coexist with other apparatuses in the active EM environment with fewer problems, increasing their perceived quality.
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Frequently asked questions
An electrical impulse, in the context of television, refers to a sudden burst of electromagnetic energy that can interfere with TV signals and reception. This is often referred to as electromagnetic interference (EMI) or television interference (TVI).
There are various sources of electrical impulses that can cause TV interference. Some common sources include:
- Spark discharges from natural or artificial sources
- Operation of radio transmitters
- Computers and other digital electronic equipment with rapid switching circuits
- Lights and power supplies
- Electric motors and ignition systems in vehicles
- Electrical appliances such as kettles, especially during commercial breaks of popular TV programmes
Electrical impulses can disrupt TV signals in several ways. They can cause pixilation, distortion, or even a blank screen. In analog television broadcasts, interference may result in multiple impressions of the same image ("multipath" reception) or tearing and loss of synchronization.
To reduce TV interference caused by electrical impulses, it is recommended to maintain a distance between TV equipment and potential sources of interference. Additionally, identifying the source of interference by cutting off power to each item one at a time can help pinpoint the culprit. In some cases, an attenuator can be inserted in the antenna lead-in wire to reduce signal overload.
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