Longer-Range Directional Antennas
Although most indoor systems do not require high-gain
directional antennas, in some circumstances you might use a 10- or 13-dBi Yagi
indoors to cover areas such as long corridors or long runs between high shelving
(such as in a do-it-yourself homeowners' warehouse). In these cases, the Yagi
can provide the necessary long-range, narrow-focused beams.
For longer outdoor links, a parabolic dish antenna might be
required. For both the Yagi and parabolic dish antennas, when mounting, be sure
to not only consider the horizontal beam width, but also the vertical beam
width. Most dish antennas are provided with adjustments for vertical alignments,
and some Yagi antennas have optional mounts to permit vertical alignment as
well.
Figure B-10 shows a
Cisco 13.5-dBi Yagi antenna. This might look similar to antennas you have seen
from Telex, Proxim, and others, because it is sold by many different
manufacturers as an OEM product.
Table B-8 lists the
specifications for the Telex 13.5-dBi Yagi antenna.
Table B-8. 13.5-dBi Yagi Antenna
Specifications
|
Parameter |
Specification |
|
Frequency range |
2.42.83 GHz |
|
VSWR |
2:1, 1.5:1 nominal |
|
Gain |
13.5 |
|
Front-to-back ratio |
30 dB |
|
Polarization |
Vertical |
|
Azimuth (3-dB BW) |
30 degrees |
|
Elevations (3-dB BW) |
25 degrees |
|
Dimensions |
18" * 3" |
|
Wind rating |
110 mph |
Figure B-11 shows a
Cisco 21-dBi solid parabolic dish antenna. As with the Yagi, this particular
antenna is sold by many different vendors as an OEM product.
Table B-9 lists the
specification for the 21-dBi dish antenna.
Table B-9. 21-dBi Parabolic Dish Antenna
Specifications
|
Parameter |
Specification |
|
Frequency Range |
2.42.83 GHz |
|
VSWR |
1.8:1, 15:1 nominal |
|
Power |
5 watts |
|
Gain |
21 dBi |
|
Front-to-back ratio |
25 dB |
|
Maximum side lobe |
17 dB |
|
Polarization |
Vertical |
|
Azimuth (3-dB BW) |
12.4 degrees |
|
Elevation (3-dB BW) |
12.4 degrees |
|
Dimensions |
24" * 15.5" |
|
Wind Rating |
110 mph |
 | 
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