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Nesis III User's Manual
• When a mode S transponder is installed in an aircraft, it does not nec-
essary mean that it also transmits ADS-B out signal.
• Intruding traffic with C-mode or even S-mode transponder without
ADS-B out signal are all non-directional targets. In addition, distance
to the target is estimated from the signal strength. All this means that
values shown in traffic warning window are not very reliable for non-
directional targets.
Please note that web pages are often reorganized and that manuals, firmware
and FAQ can be moved to some other place.
5.1
Directional and Non-Directional Traffic
Power Flarm and other compatible devices consist of two independent sub-
systems merged into one device. The first is Flarm subsystem and the second
one is ADS-B in subsystem.
5.1.1
Flarm Subsystem
The Flarm subsystem is only capable to see other aircraft that are also
equipped with Flarm devices. The range of visibility varies significantly and
depends on the antenna position, antenna shadowing, device strength, air-
craft material . . . The range is about 10 km at best but may be significantly
less in reality. It can be as low as a few hundred meters and blind spots are
also possible. When the device detects a target – an airplane which has also
a Flarm device on board, it will get a full set of target data: type, position,
speed, etc. This is a directional traffic (or directional target). Flarms are
mostly installed in gliders.
5.1.2
ADS-B in Subsystem
The ADS-B in subsystem listens to transponder replies of other aircraft –
targets. Here are two possibilities:
• The transponder reply comes from an aircraft, which is equipped with
ADS-B out. In this case, the transponder reply also holds information
about aircraft position, speed, direction, etc. Not many small airplanes
are equipped with this. This kind of equipment is mostly found in
airliners and in "more serious" aircraft. Most small GA aircraft and
ULMs do not have such equipment.
5.1 Directional and Non-Directional Traffic
65
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