1-1
SECTION 1. GENERAL RADIOTELEMETRY NETWORK
1.1 INTRODUCTION
Data retrieval from a remote site can be difficult.
To accomplish data collection from isolated
sites Campbell Scientific, Inc. utilizes a
radiotelemetry network. Dataloggers can be
accessed by radiotelemetry which requires no
physical connection from the computer to the
datalogger. The radiotelemetry link reduces the
number of visits to a remote site for data
collection.
The radiotelemetry network is designed for
complete computer control. One computer can
establish communication with up to 254 remote
sites (150 per RF232T). The RTMS allows data
collection from the datalogger, transmitting
datalogger programs, and displaying current
readings from the datalogger.
The requirements specific to a radiotelemetry
network include:
•
The distance between radio stations should
not be greater than approximately 25 miles.
•
The stations should not have major
obstacles between them, therefore, they
should be within line-of-sight of each other.
The stations communicate over a radio
frequency which is specified in Megahertz
(MHz). A data communication network must
have its own specific frequency to prevent
interference from other sources. Typical radio
frequencies are either VHF (Very High
Frequency) ranging from approximately 130 to
174 MHz or UHF (Ultra High Frequency)
ranging from approximately 403 to 512 MHz. A
typical RF system is shown in Figure 1-1.
Telemetry network’s three basic components
are:
•
Field Station
•
Base Station
•
Repeater Station
FIGURE 1-1. A Basic Radiotelemetry Network
