Low-Power Radio and Telemetry Products

Although there is presently considerable market focus on 2.4 GHz ISM-based networks,
there are many radio channel allocations at lower frequencies that support radio telemetry
and telecommand applications. The RF channel spacing may be either 12.5 kHz, 20
kHz, or 25 kHz, and the allocations can be anywhere between 100 MHz and 860 MHz.
Products tend to be divided into very low power (1 to 10 mW) SAW filter or crystalbased
devices, quite low power (500 mW), or reasonably high power (2 W). Very low
power devices are used for applications where very low power consumption is
needed—devices installed on pipes underground, for example, which need to be
remotely interrogated occasionally from the surface (sleeper meters).
Typically the products can be configured to work at VHF (125 to 180 MHz), UHF
(400 to 500 MHz), and in the band allocated within Europe between 868 and 870 MHz.
Range and data throughput are dependent on power output and receive sensitivity.
Table 15.3 shows a typical product specification.

One of the problems with the telemetry and telecommand market is that spectrum
allocations differ from region to region (the United States, as always, is different), and
this makes it difficult to achieve economy of scale in terms of RF hardware. In terms of
software, some commonality is emerging in that IP protocols are being used increasingly.
The IETF Simple Network Management Protocol (SNMP) helps improved application
transparency. Software code for a utility meter reading application in the United
States, for example, does not need to be completely rewritten for a utility meter reading
application in Europe.
VHF and UHF telemetry is used very successfully in motor racing to monitor and
manage engine performance and driver performance (our previous heart-rate example).
This is a very high mobility (over 200 mph) application and also can be quite
broadband, because there is a lot of engine information to capture. It is actually easier
to deliver broadband to a fixed rather than moving object, as we will see in our next
section.