Sennheiser SKM 500, Manual

Page: 91 / 204

88
Diversity reception
The EM 500 receiver operates on the “True Diversity” principle:
A receiving antenna receives not only the electromagnetic waves which reach
it by a direct path, but also the reflections of these waves which are created in
the room by walls, windows, ceilings and fittings. When these waves are
superimposed, destructive interference occurs, which can also be called “field
strength gaps”. Repositioning the receiving antenna can bring a solution,
provided the transmitter remains in its original position. With mobile
transmitters, however (which all radiomicrophones are ), the “field strength
gap” will then occur with a different transmitter position. These “field strength
gaps” can only be eliminated with true diversity receivers.
In true diversity, instead of one antenna and one receiver there are now two
antennas and two receiver sections. The antennas are spatially separated. By
means of a comparison circuit, the receiver section with the strongest RF
signal is always switched to the common AF output. The risk of the occurrence
of “field strength gaps” in both antennas at the same time is virtually
nonexistant.
The receiver display panel shows the active diversity section (I or II).
Receiver section I Receiver section II
Electronic
switch-over of
AF signal
Control signal Control signal