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4.4 Testing the coverage area
To make sure that the whole area is covered with
adequate IR radiation and avoiding thus black spots, an
extended reception quality test should be done. The test
can be done in the follow way:
Testing during installation
1. Check that all radiators are connected and
powered up;
2. Set the transmitter in the Test-mode (see section
2.6.9). For each channel, a test tone frequency will
be transmitted;
3. Set a receiver to the highest available channel and
listen to the received signal through the
headphones;
4. Test all positions and directions (see next
paragraph).
Testing all positions and directions
Walk around the conference venue under the test mode
of the transmitter; test every position where the signal
must be received. If an area is detected as having bad
reception or even no reception at all, two main causes
should be taken into consideration:
■
Bad coverage
The receiver cannot pick-up adequate infrared
radiation. This may be because the tested position is
out of the footprint of the installed radiators or the
radiation is blocked by obstacles such as a column, an
overhanging balcony or other large objects.
Check whether you used the correct footprints for the
system design or not. Check if the radiators used have
a) sufficient output power and b) are not switched to
half power operation by mistake. If bad reception is
caused by a blocked radiation path, try to remove the
blocking obstacle or add an extra radiator to cover the
shaded area with more IR energy.
■
Black spots
IR signals coming from two radiators may cancel out
each other (multipath effect) when reaching the
receiver. Bad reception only happens on some special
path. Multipath effect is confirmed being the cause of
bad reception if the bad signal received by the receiver
is improving the instant a radiator is a) changing the
direction of the receiver b) shaded-off or simply
switched-off. IR radiation, reflected from a surface with
a high reflectivity may also cause multipath effect.
Check that the signal delay compensation switches on
the radiators are set to the correct value. Check the
system design. If necessary, reduce the distance
between the two radiators that cause the problem
and/or add an extra radiator.
Please note that due to the physical characteristics of
the signal distribution, it is not possible to avoid
multipath effects completely.
