7/Telemetry Radios
Software Monitoring and Control
By now, you may have noticed one very important thing about
RC transmitters: they only send communications in one direc-
tion, from the transmitter to the aircraft. In order to gain access
to any of the onboard data from your aircraft, we have to use a
special two-way radio that is known as a
telemetry link
.
Pick the Right Frequency
Telemetry radios operate on two standard frequencies. In the
United States, we typically use the 915 MHz band, while the 433
MHz band is favored in Europe. These standards are estab-
lished to help avoid interference from other electronics on the
open market. Operating on the wrong frequency band can be
illegal in certain parts of the world. Be sure to check the laws in
your country to see what standard you should use.
Just as its name implies, the telemetry link takes a series of
measurements from your aircraft and sends them back down to
the ground where they can be displayed in ground control soft-
ware (
). In addition, data—such as waypoints, autono-
mous flight missions, and aircraft configurations—can be com-
municated up to the aircraft from the same ground control
software.
Having access to this type of information while you are still
safely on the ground can be a huge advantage. It can help you
identify problems before they get out of hand. Some of the data
points your ground control software needs are latitude, longi-
tude, altitude, aircraft attitude, current battery voltage, aircraft
heading, speed and duration of flight, plus many more. You can
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