Advanced radio cells AR1255, Physical Planning And Installation Manual, Page: 19 / 48

March 1, 2002 Page D2
Antenna and Frequency Planning
Antenna Patterns
Horizontal
The ARCi standard hub antenna is moderately directional, transmitting and receiving in a
coverage pattern 60 degrees wide
1
. This means that the geographic coverage of the antenna is
30 degrees on each side of a line drawn straight out from the front of the antenna. Geography
further to the sides or rear of the antenna receives increasingly less signal.
Therefore, a system where the hub location is roughly in the center of the geography to be
served would probably employ six ARCi hub antennas (each with its own integrated electronics)
aimed 60 degrees apart to complete the circle of coverage. A hub located at one side of the
coverage area might only require 3 hub antennas to provide 180 degrees of geographic coverage.
Vertical
Similarly, the antenna is directional in the vertical plane
2
. This means that elevations above
straight out from the front of the antenna (up in the sky) receive less power, as do elevations
below straight out. Therefore, the antenna is normally pointed at the furthest subscriber to be
served, with the lower elevations providing appropriately less power to closer subscribers.
Antenna Patterns
See the Antenna Patterns section of this manual for measured plots typical of ARCi antennas.
Other Antenna Configurations
Contact ARCi for other antenna configurations. FCC regulations require that the combination of
the actual power output of the ARCi transmitter and the gain of the antenna
together
do not
exceed specified limits.
Frequency Planning - Downstream
Available Channels
There are 16 available downstream channels in the ARCi standard frequency plan. The
downstream frequency is established by the front panel control of the upconverter. The
displayed frequency on the upconverter (in MHz) is the center of the 6 MHz wide downstream
signal.
1
ARCi’s standard antenna has a so-called “half power beam width”, or “3 dB beam width” of 60 degrees in
the horizontal plane. The ARCi 2001, beta units have 3 dB beam widths of 45 degrees.
2
The 3 dB beam width in the vertical plane is 3 degrees.