Antenna installation, Antenna installation -13 – NETGEAR ME103 User Manual

Page 63

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Reference Manual for the ME103 802.11b ProSafe Wireless Access Point

Advanced Configuration


August 2003

Antenna Installation

The ME103 comes with two removable 2-dBi antenna. Two antennae provide what is called
“space diversity”, which helps to combat the addition of electromagnetic waves in the space where
the unit is installed. This effect is called “multipath fading.” Multipath fading is generated by the
multiple reflections of electromagnetic waves in an office due to walls, ceiling, floors, partitions,
doors, metallic polls, cubicles, etc. and the motion of people and objects. The benefits of two
antennae are evident when there is distance or obstructions in the line of sight between the ME103
and the clients. When only one antenna is used, a degradation of up to 50% of data throughput can
be noticed in several spots of the coverage and also at the fringes of the range.

The two 2dBi antenna are dipole and use vertical polarization. They provide an optimal radiation
pattern in the plane perpendicular to their direction. When oriented vertically, they provide a
optimal range in the horizontal plane (horizontal donut shaped signals). If the office is small and
on multiple floors, it is advised to put the antenna flat so that the maximum coverage is vertical
rather than horizontal. When the office is an odd shape, NETGEAR advises you to do some
orientation trials.

For applications requiring more range, wireless accessories can be used such as external antennae
and bi-directional booster(s). The first optional update is replacing the two 2dBi antennae by two
5-7dBi dipole antennae. Simply turn the ME103 off, unscrew the two antenna, and screw on the
new ones. Be sure to use antenna with a reversed SMA connector.

Another solution is to relocate the antenna(e) with an RF cable to an optimal spot such as a ceiling,
high on a wall, etc. One typical application is to locate the ME103 is in a secure location like a data
center. Two external antenna are placed outside the room, for example on the ceiling, and
connected with RF cables to the ME103. Another application is two external directional antennae,
one pointing to one side of the building, and the other to the other side. Be aware of the loss in the
cable. If the cable is too long and used with a medium gain antenna, the gain from placing the
antenna in good spot may be reduced or eliminated. Only high gain antenna (more than 10dBi)
should be used with a long cable such as 5 or 10m.

To cope with this inherent limitation, NETGEAR also provides bi-directional booster. This
component amplifies the RF signal in transmit mode and in receive mode. It automatically
switches itself to the receive or transmit mode. The booster is placed very close to the antenna and
provides an outstanding output RF power of 500mW or 27dBm. It also includes a low noise
amplifier for the receive path of 10dB gain minimum. The antenna and booster can be connected
with a cable as long as 10 to 15m from the ME103 without any performance reduction.