Problems in DTT reception? The weirdest origins of television interferences
Sometimes, at regular intervals, DTT cannot be properly received, or the picture becomes pixelated/blurried at a certain moment. In other cases even cars on the street can generate electromagnetic interferences. All these problems can certainly be solved, but firstly we need to identify them.
Even the most skilled professionals sometimes are unable to easily find the origin of an interference that is causing the picture to pixelate/blur, or the DTT signal to be interrupted or even unable to be received. In this article we are listing the most surreal known sources of problems in digital terrestrial television reception.
The enemy is at home: Appliances causing interferenceDO YOU THINK PROMAX ANALYZERS CAN HELP YOU? ASK AN EXPERT
- LED lighting. Those lamps featuring low quality power supplies may introduce noise in the electrical network that could have an impact in the DTT receiver’s power supply. A ferrite core around the LED lamp wiring can solve the problem.
- Wireless routers. It is bad practice to place them near TV sets. Changing their location solves the problem.
- Electrical motors. Refrigerators, extractor hoods, vacuum cleaners, washing machines, drills… An electrical engine will cause problems in DTT reception if the connections wiring are in poor condition or they are not correctly deployed.
- Thermostats in boilers or water heaters. When their electronic circuitry becomes damaged, they can cause interference for some seconds as they switch on. That is enough time to lose the television signal.
- Photovoltaic solar plates. The inverters used in PV solar plates may produce electric induction when they feature poor isolation and filtering.
Problems with neighbors: Interference comes from abroadPROMAX TV AND SPECTRUM ANALYZERS SPECIFICATIONS
- Cars and motorcycles that cause interruptions in DTT signal as they drive nearby. It may happen when the spark plugs of the vehicles are poorly insulated and the television network uses wideband amplifiers. Whenever possible, the solution is using single channel amplifiers or at least using a coax cable with higher quality shielding.
- Buildings under construction. A new, nearby construction may cause the antennas to receive echoes not present at the time the antenna was installed. The solution is realigning the antenna using the dynamic echoes analyzer in the TV analyzer.
- Yagi antennas in reception radiating signal. A poorly filtered installation causes DTT antennas used for reception to also radiate signal. A field analysis using directive antennas can find the antenna that is causing the interference.
- Adjacent channel interference. This happens when a DTT channel partially overlaps a neighbouring channel. This is very difficult to solve from the receiver’s side, beyond aligning the antenna to other emitter or receiving television from another source: Optical fiber, satellite, cable or DSL.
Interferences from a natural sourceDO YOU THINK PROMAX ANALYZERS CAN HELP YOU? ASK AN EXPERT
- Trees can block television signals between the emitter and the receiver, especially when using indoor DTT antennas. The solution is installing antennas high enough on the rooftop. In addition, the problem will occur seasonally when dealing with deciduous trees: Spring/summer will be more likely to lead to reception problems than fall/winter when trees lose their leaves.
- Fading effect in the coast. Humidity, temperature and tides cause great signal fluctuation over the course of the day. It can be mitigated using a higher quality antenna accurately aligned using a TV analyzer.
- Electrical fences are a source of electromagnetic interference if they are not properly grounded or when vegetation makes contact with the electrical wire. A simple periodic maintenance solves the problem. Also, the fence should not be installed in parallel to power or phone lines.
- Birds perched in antennas may have an impact in the reception quality. This was vital in the analog TV era, but it is also critic in DTT in poor reception areas. It is possible to install anti bird spikes in the antennas as long as they are made of plastic. Using metallic spikes lower the antenna properties and performance.
Avoiding bad practices when installing television networksPROMAX TV AND SPECTRUM ANALYZERS SPECIFICATIONS
- Cable rolled up in loopcan act as an antenna and capture external radiofrequencies.
- Electrical wiring must run away/far from the coax wiring. In local CATV networks, if coax cable runs too near to the public lighting electrical network, when the latter turns on it will cause quality degradation.
- Analyze possible 4G/5G interference using professional TV analyzers that include specific functions to locate them and install filters if required, specially on those installations using wideband amplifiers.
- Damaged wiring whose plastic jacket is cracked. Not only the shielding becomes rusty but also they can act as a pipe and transport water to the antenna equipment, disabling it.
PROMAX is a leading manufacturer of test and measurement systems, broadcast and TV signal distribution equipment. Our product lines include measuring instruments for cable TV, satellite TV, broadcast, wireless and fibre optics networks, FTTH and GPON analyzers. DVB-T modulators, IP streamers or IP converters (ASI, DVB-T) are among the company’s latest developments.