Intermec MobileLAN 21 Series, System Manual, Page: 60 / 275

MobileLAN access 21XX System Manual
2-20
Positioning Antennas for Antenna Diversity
The 802.11b radio features antenna diversity, which means that two antennas can be
attached to a single radio. If you are using two antennas for one 802.11b radio,
placement of the antennas is critical because each antenna has a particular function.
Antennas placed too close together may cause interference with each other. Antennas
placed too far apart may not be able to establish two-way communications with other
radios. To achieve optimum placement for the two antennas, you must place the
transmit/receive antenna so that it is within range of all the radios that the receive-only
radio can hear.
Note these important points about antenna placement for an 802.11b radio:
•
Use external antennas to achieve the recommended antenna separation for
placement of either omni or directional antennas.
•
Position directional antennas so they point in the same direction.
•
Follow the recommended antenna separation precisely when using the closest
distances. Movement of as little as 3.05 cm (1.2 in) may strongly affect
performance.
•
Position the antennas so that both antennas are within range of the radios they need
to communicate with.
•
Do not position the two antennas around a corner or so that a wall is between them.
The recommended antenna separation is listed in this table. You should choose the
greatest distance possible within the constraints of your environment.
Location Recommended Antenna Separation
Highly reflective warehouse environment 0.33 m (13 in) or 0.64 m (25 in)
Moderately reflective warehouse environment 0.64 m (25 in), 1.22 m (4 ft), or 1.83 m (6 ft)
Open/Office environment 1.22 m (4 ft) to 3.05 m (10 ft)
Positioning Antennas for Dual Radios
These recommendations apply to omni antennas; if you are using gain antennas, you
should increase the separation between the antennas.
•
If your access point has two 802.11b radios, position the antennas for one radio at
least 3.05 m (10 ft) from the antennas for the other radio.
•
If your access point has two radios and one of the radios is an 802.11b radio, cable
the antennas for the 802.11b radio at least 3.05 m (10 ft) from the access point.
•
If you are using more than one antenna for one 802.11b radio, position the antennas
at least 0.61 m (2 ft) apart.