Mechanism

When system components are excited by electromagnetic waves having wave lengths of the measurements of these components, energy is radiated and is transferred across the electromagnetic field to the receivers. Antennas which can be made of loops, dipoles or single ground lines act as susceptible equipment.

Well known sources of interference are:

  • Insufficiently shielded high frequency devices

  • Radio and television

  • Fluorescent lamps

  • walkie-talkies, cellular telephones

Size of the interference

The intensity of the excitement and radiation depends on the ratio between measurement and wave length. The amount of received voltage can be estimated at:

Character definitions

Character

Meaning

U0

Received voltage in the susceptible equipment

E0

Electrical field strength at the receiver

heff

Effective antenna height
NOTE:

  • The radiating coupling becomes interesting with interference signal frequencies of 30 MHz and higher.

  • The interference is at its strongest if the length of the "Antennas" are a multiple of the wave length.