User's Manual

47
Brand of ACOEM
Chapter 7
RADIO INSTALLATION GUIDELINE
RF planning should be considered from the onset in order to determine the sensor locations
and options for the Gateway installation. In the vast majority of cases, the RF requirements
do not impede a sound mechanical installation of the Eagle Field Devices but by considering
the RF implications from the start a very good first-time success rate is achieved.
The typical link budget calculations that are used in radio planning are not valid in the vast
majority of industrial environments and accurate RF modelling is far too time consuming to
be practical. For this reason, the RF planning is simply guided by empirical data gathered
from a vast array of previous installations. A set of best practices are presented which are
effortless to follow yet delivers reliable performance without the need for calculations or
sophisticated survey equipment.
1. INITIAL SITE SURVEY
Conduct the first site survey in order to determine the points that require monitoring and
identify potential Gateway and antenna locations.
Choose the location that offers the smallest distance to the farthest group of Eagle Field
Devices.
Be aware of the RF cable loss if the antenna will be placed far from the Gateway and bear in
mind that every 3dB loss will roughly reduce the range by 30%.
Test the reception of the farthest sensors or those with doubts about their reception because
of their situation (metallic surroundings, casing, guards...).
2. CHOOSE A SUITABLE ANTENNA
In order to select the correct antenna for the Gateway and ensure a successful installation, a
basic understanding of antenna specifications and how they operate is presented.
2.1. RADIATION PATTERN
An antenna receives a finite amount of power at its port from the Gateway and focuses this
power when transmitting it according to its “radiation pattern” which is simply describes how
the antenna focuses the transmitted power. The antenna will focus the power more in one
direction than another an important concept to grasp is that when it focused more power in
one direction it has to take that power away from other directions. That is why a higher gain
antenna has a narrower beam width.
In the same narrative, when an antenna is listening more intently in a direction it will have a
diminished “listening” ability in other directions. Antennas also behave according the physical
law of reciprocity, meaning that the focus of an antenna’s “listening” ability is exactly the
same as its transmitting focus. In other words, the “radiation pattern” is identical to its
“reception pattern”.
It is best practice to choose an antenna with a radiation pattern that will focus as much
power in the direction of the Eagle Field Device installation and not waist energy in directions
where there are none. For example, use a sector or panel antenna and not an
omnidirectional antenna if it is located at the one end of all the Eagles.
Some common antenna types are shown below together with an illustration of their radiation
patterns.