© Microhard Systems Inc.
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7.0 Installation
The are a number of factors to consider when preparing to deploy a radio network, several of
which have been touched-upon or detailed elsewhere within this manual. Following is a list-
ing of a number of factors, in no particular order:
Network Topology
Section 5.0 detailed the various network topologies which the Nano will support. Determine
which topology is suited to your specific requirements.
Throughput
The n920/2420F is capable of 230.4kbps asynchronous serial data throughput. The network
topology has an effect on how this available throughput is ‘shared’ between all nodes on the
network.
Distance
The physical distance between the modems dictates such things as required antenna perfor-
mance and heights, and whether or not a Repeater(s) is required. When contemplating an-
tenna types and Repeater sites, keep in mind the directivity (omnidirectional or directional) of
the antennas being used, and also recall the effect of a Repeater on throughput (see Section
4.4).
Terrain
Along with distance, the terrain is a very important consideration with respect to antenna
height requirements. The term ‘line-of-sight’ (LOS) refers to being able to ‘see’ one location
from another - a minimum requirement for a radio signal path. In addition to LOS, adequate
clearance must also be provided to satisfy ‘Fresnel Zone’ requirements - an obstruction-free
area much greater than the physical LOS, i.e. LOS is not enough to completely satisfy RF
path requirements for a robust communications link.
Transmit Power
Having read thus far through the factors to be considered, it should be clear that they are all
interrelated. Transmit power should be set for the minimum required to establish a reliable
communications path with adequate fade margin. Required transmit power is dictated primar-
ily by distance, antenna type (specifically the ‘gain’ of the antennas being used), and the re-
ceive sensitivity of the distant modem. Cable and connector losses (the physical path from
the modem’s ‘antenna connector’ to the antenna’s connector) must also be taken into ac-
count.
Receive Sensitivity
The Nano Series has exceptional receive sensitivity, which can produce a number of benefits,
such as: added fade margin for a given link, being able to use less expensive coaxial cable
or antenna types, being able to operate at greater distances for a given distant transmitter
power (perhaps negating the requirement for a Repeater site!). Distance, antenna gain,
transmit power, and receive sensitivity are critical ‘numbers’ for radio path calculations. For-
tunately, the Nano Series features the maximum available transmit power combined with ex-
ceptional receive sensitivity - two ‘numbers’ which will produce the most favorable path cal-
culation results.
The installation,
removal, or
maintenance of any
antenna system
components must be
undertaken only by
qualified and
experienced
personnel.
