User's Manual
DragonWave Inc.
40
Horizon Compact Release 1.01.01 Wireless Ethernet Product User Manual – Volume 1
9.2 Three Important Factors
When you prepare to align the radio antennas , you must consider three important factors:
1. the radiation patterns of dish antennas (main lobe and side lobes)
2. the need for a Clear Line of Sight (LoS)
3. the sensitivity of the alignment adjustment
9.2.1 Antenna Radiation Patterns
The dish antennas used for the DragonWave Horizon Compact have high gains and very narrow beam
widths, making antenna alignment a critical element of a successful installation. In addition to the main
antenna beam, or lobe, there are often side lobes. Care must be taken to ensure that alignment is made
to the main lobe and not onto a side lobe. If you align onto a side lobe, the RSL will be at least 20dB less
than expected.
Table 9-1 Antenna Gains and Beam Widths – Selected Frequencies
9.2.2 Clear Line of Sight (LoS)
The DragonWave Horizon Compact requires a clear LoS between the units at each end of the link. You
must be able to see an unobstructed view of the antennas from each end. Avoid obstacles that are close
to the LoS mid-way between antennas, but not blocking it, as this can have a negative impact on signal
quality (Fresnel zone clearance). Also, ensure that antennas are mounted with adequate clearance from
roof tops, roof edges, walls and other obstacles (e.g. air conditioning plant) to avoid problematic near field
effects.
9.2.3 Alignment Adjustment Sensitivity
When aiming the antenna it cannot be over emphas ized that you must rotate the adjustment nut(s) 1/10
th
of a turn at a time between taking RSL readings (allow time for the RSL reading to update). One full turn
of the adjustment mechanism can move the antenna through 1.6 degrees azimuth or 2.2 degrees of
elevation. Table 9-1 shows that the beam width of the typical antenna is often less than the amount of
movement available with one full turn of the aiming adjustment.
18 GHz Horizon 23 GHz Horizon Antenna
Size
Beamwidth of
main lobe
(degrees, 3 dB)
Gain
dBi
Beamwidth of
main lobe
(degrees, 3 dB)
Gain
dBi
30 cm/12” 3.0 degrees 34 2.7 degrees 35.1
60 cm/24” 2.0 degrees 38.6 1.7 degrees 40.2
90 cm/36" 1.3 degrees 42.0 1.1 degrees 43.7
120 cm/48”
1.0 degrees 44.5 0.8 degrees 46.2