2 - 14
Description varix 200/varix 14 (DECT)
2 Planning a cordless communications network
- External antennae should be installed side by side, not above one another. External pairs
of antennae should be installed observing minimum spacing of 20 cm between antennae.
Avoid installing at a distance equal to a whole multiple of the wavelength (16, 32, 48 cm
etc.).
- Directional antennae can be used to supply large areas with a low level of telephone traf-
fic.
In order to cope with high traffic levels, the radius selected for a radio cell should even be
reduced. In this case, increasing the covered area by the use of directional antennae has
little effect.
- Both directional antennae must point in the same direction.
Each of the two antennae should be able to switch over to the other in case the reception
on one is poor. Since signal interference cancellation points only occur at specific physical
locations, switching antennae can help solve reception problems. In order to be able to
use this effect, however, the antennae must point in the same direction.
Interference cancellation points: a location where two or more high frequency signals over-
lap in such a way as to cancel each other by interference. Cancellation is caused by
beams with different propagation times being reflected from objects.
2.5.3
Installation of FPs
The following observations apply to rooms with a "normal" ceiling (2.80 m). In rooms with a
ceiling height of 3 metres or more, the ideal height at which to mount an FP increases
accordingly.
Ensure a minimum clearance of 50 cm to the ceiling in order to avoid unnecessary reflec-
tions.
The base station is usually mounted on a wall. The higher it is positioned, the greater in most
cases the subsequent range. An ideal mounting position would be between 1.80 and 2.30
metres above the floor. Installation below 1.80 m should be avoided (average height of
humans and furniture), as experience has shown that this leads to considerable problems.
These are due to the fact that a PP is usually held at head height when in use. The antenna
should have a slight downward characteristic in the direction of the PP. If the mounting posi-
tion is lower, then the beam has to penetrate furniture and other objects inside the customer's
rooms. This would result in the field strength decreasing even further, due to additional attenu-
ation caused by the assorted objects inside the room.
Note:
Install the FPs as high up as possible, but at a minimum distance of 50 cm to the ceil-
ing and walls.
