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Telemetry Receivers
Peter Parker aka Spiderman, once said, "With great power comes great
responsibility". While we don't have Parker's résumé, he may have
temporarily worked as a telemetry technician before opting for a
relatively relaxed profession of freelance photography. To
understand the responsibilities of a telemetry technician, one needs
to understand telemetry first. Telemetry or "remote measurement" is
a highly automated communications process by which measurements are
made and other data collected at remote, inaccessible or dangerous
places, such as orbiting satellites, and then relayed to receiving
stations on ground for display, monitoring, and recording.
The telemetry technician has a wide variety of career opportunities
which may include monitoring of large, complex systems such as
chemical plants, oilrigs, satellites, electric power plants,
gathering meteorological data, remote meter reading, logistics
management, tracking endangered land and marine species, real time
physiological monitoring of patients, and monitoring manned and
unmanned space flights. If you are a telemetry technician charged
with the maintenance of a telemetry service of any type, it is
suggested that before your accept the contract, you or the owner of
the equipment take possession of a service manual for that
particular system. Essential information required for any effective
servicing work includes the following:
- Assigned carrier frequency for the system
- Type of modulation, bandwidth (deviation), and maximum data rate
- Level and frequency of all pilot tones and sub-carriers
- Significance of each frequency in the modulation bandwidth
- Expected signals at input and output test points for each
sub-section
- Sense of logic, baud rate of data and error correction scheme
If the source of the data is a remote station, which forms an
integral unit with the radio equipment, you will also need
information on the type and location of the sensor supplying the
original information and details of any preliminary data processing
that may be done before the input to the radio link. The telemetry
technician in command of this great technology should monitor it
conscientiously. For instance, for many environmental monitoring
duties, such as stream gauging or automatic weather stations, the
measurement values are unlikely to change significantly for many
hours at a time. In such cases, it would be grossly uneconomical in
terms of both electrical power and use of spectrum space to run the
telemetry transmitter continuously.
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