Flat panel TV's and radiation

All electrical appliances can emit radiation. Some are designed to do just that. A mobile phone emits electromagnetic radiation. It must in order to do it's job. An electric heater emits infra-red radiation. All lights emit visible light radiation as well as some infra-red and ultraviolet radiation.

This is a short article discussing incidental radiation from TV sets. I have been asked for comment in connection with my earlier article about how close you should sit to a TV set. I should say from the outset that these kinds of radiation are NOT the sort you find in a nuclear reactor. It is unfortunate that people do confuse nuclear radiation (ionising) with the much safer non-ionising type such as heat/light/electromagnetic radiation that we commonly find in our everyday life. We are in fact just using the term to describe something that 'radiates'.

CRT Televisions

Remember these? Cathode-ray tube TV's. The big, really heavy televisions which took up a lot of space and which might be a museum piece before too long. They might not be high-definition, but they displayed moving pictures a lot better than these modern LCD and plasma gizmos.

The CRT TV produced magnetic fields at 50Hz and at 15,625Hz.(PAL) They also produced electric fields of the same frequencies and they had to be built carefully to avoid producing X-rays due to the high voltages used internally. The U.S FDA regarded all of these radiated fields as being too low to be harmful to humans at typical viewing distances even in the long term.

LCD Televisions

These produce no magnetic field and only very weak electric fields. There is a tiny amount of infra-red radiation emitted, which needs specialist equipment even to measure. LCD sets are extremely safe to be around and neither are they known for causing interference to radio.

Plasma Televisions

These produce no magnetic field but do radiate small electric fields due to the constant charging and discharging of the plasma cells with relatively high voltages. Still, these fields are very weak and are regarded as very safe for humans. Plasma TV's are known to interfere with AM radio, due to the rate of change of the electric potential driving each plasma cell. The radio usually has to be located fairly close to the TV and be tuned to a weak radio station for it to get interference though.

The need for shielded centre speakers

Finally, it was common for the centre speaker of a home-theatre system to be shielded. This was because the magnetic field generated by an unshielded speaker could cause colour blotches on CRT type TV sets. Usually the centre speaker is located close by; either on top or underneath the TV set.
It is not necessary to use shielded speakers in conjunction with an LCD or plasma set.

Axino-tech Consulting & Services , January 2011.