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16.4 Shielding
Metallic building parts, furniture, wall coverings etc. shield electromagnetic waves. This produces what are known as radio
pockets where direct reception is not possible. Receivers can no longer receive the transmitter signals directly.
Radio pockets caused by a metal cabinet, for example
16.5 Reflexion / reflection
Furthermore, radio waves can be reflected by metal objects or surfaces. When this happens, they can either be allowed
to pass with great losses or reflected in full (and with a delay). In most cases, reflections are annoying and not desired.
They trigger polarisation and interference (see below).
However, the radio waves can still reach their destination by diverting to certain objects. Longer transmission paths in
particular can be bridged using reflexion.
Whether this works in your particular situation, depends greatly on the prevailing conditions and should be tested on a
case-by-case basis.
Examples of reflective media:
•
Reinforced concrete walls
•
Metal cabinets
•
Mirrors with metallic surface
Reflection of the radio signal
Metal cabinet
Transmitter
Wall
Reflection
Receiver
Receiver
Transmitter
