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1
Introduction
4
Selecting an Antenna
The following table shows guidelines for selecting antennas based upon their gain
properties (expressed in decibels (dB)). The gain of any antenna is essentially a
specification that quantifies how well that antenna is able to direct the radiated radio
frequency (RF) energy into a particular direction. Thus, high-gain antennas direct their
energy more narrowly and precisely, and low-gain ones direct energy more broadly.
The range estimates listed are those that can be expected between two 3Com Wireless
Building-to-Building Bridges using the listed antenna combinations.
9
a
Gain
Antenna A
4
4
8
4
4
8
8
13
13
b
18
a.
Gain is shown in dB
b.
18 dB antenna typically paired with 50-ft cable accessory
Antenna Options
The following 3Com antennas are available for use with the 3Com Wireless Building-to-
Building Bridge:
3CWE490 4 dB Omnidirectional
I
3CWE491 8 dB Omnidirectional
I
3CWE495 13 dB Bidirectional Panel
I
3CWE496 18 dB Directional Panel
I
Selecting a Cable
Specific cables are available from 3Com for connecting the wireless bridge to an antenna.
In planning your bridging topology, it is important to account for signal attenuation due
to the cable and connectors used between the bridge and the antenna. Using the shortest
cables possible reduces signal loss.
3Com recommends using 50-ft cable with 18 dB antenna (with 10 dB attenuation) for
typical installations.
Cable Options
The following 3Com cables are available for use with the 3Com Wireless Building-to-
Building Bridge:
3CWE480A — 6 ft
I
3CWE481A — 20 ft
I
3CWE482A — 50 ft
I
Gain
Distance
Distance
Antenna B
(Meters)
(Miles)
4
522
8
827
8
1,311
13
1,471
18
2,616
13
2,332
18
4,146
13
4,146
18
3,695
18
3,293
Antenna Types
0.3
Omni-to-omni
0.5
Omni-to-omni
0.8
Omni-to-omni
0.9
Omni-to-panel
1.6
Omni-to-panel
1.4
Omni-to-panel
2.6
Omni-to-panel
2.6
Panel-to-panel
2.3
Panel-to-panel
2.0
Panel-to-panel
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