The Story: Chicken wire and EMC

Screening against electromagnetic noise

One day in 1977, DELTA (at that time named ‘ElektronikCentralen’), was contacted by telephone by a furniture manufacturer who needed urgent help to manage the electronic noise coming from the company’s glue drying machines.

The machines, which dried glued wood and used high frequency radio waves to speed up the drying process, were interfering with Fyn’s TV broadcast transmitter, and thus creating problems with the TV signal in local homes. P&T’s radio noise service had therefore asked the furniture manufacturer to do something about it immediately.

DELTA’s EMC experts visited the site and quickly identified the problem. The high frequency noise from the machines precisely matched the frequency of the signal from the TV transmitter and thus drowned out the received signal, so that the neighbours could not watch television.

DELTA recommended that the furniture manufacturer covered walls and ceiling –  where the glue drying machines were installed – with two layers of chicken wire and cast chicken wire in the floor. That helped. Now the TV signal reached the neighbouring houses clearly.

Remedying electromagnetic noise

Since the 1950s, people have used chicken wire and ‘Alukraft’ (i.e. aluminium foil with greaseproof paper backing) as a material for shielding ceilings and walls against electromagnetic noise in similar situations. The chicken wire works as a shielding material because it ensures that the radio waves remain in the room, because the mesh size in the chicken wire is smaller than the wavelength of the radio waves. A room lined with ‘Alukraft’ ensures that radio waves are reflected back and do not escape from the room.

Today, the EMC Directive would not permit any machine to emit such a level of electromagnetic noise as the furniture manufacturer’s glue drying machine did. These types of machines are still used to dry glued wood, but the machines are placed in shielded rooms, so that they do not emit interference.

Every year DELTA’s EMC specialists carry out EMC tests for many different companies and provide advice about EMC, so that the companies are sure that their products and facilities meet the requirements in the EMC Directive.

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