User's Manual

Chapter 4 – Principles of Operation
SKY899 Pilot’s Guide
4-7
Preliminary
ADS-B
The SKY899 anticipates the future Free Flight environment by
continuously monitoring the dedicated data link frequency
(
1090 MHz) for ADS-B mode S extended squitter messages
within
50 nmi. These messages are broadcast, without interro-
gation, from aircraft with
ADS-B-capable mode S transponders.
The
SKY899 does not require a mode S transponder, ADS-B-
capable or otherwise, to perform its ADS-B surveillance.
An
ADS-B message contains nav data for the intruder aircraft
including
GPS position, ident, ground speed, and intent. The
SKY899 uses this nav data along with its own aircraft GPS nav
data to calculate the relative position of the intruder to enhance
its active
ATCRBS surveillance of the intruder.