TeeJet RX 400p - Manual (Page 37)

RX 400p
2-5 98-05044
R1
default, selecting and tuning to the most appropriate beacon without operator
intervention. The RX 400p’s internal beacon receiver uses its two independent
beacon channels to identify and lock to DGPS beacons without interrupting the
continuous flow of RTCM data to the GPS receiver.
ABS mode is ideal for navigation applications over considerable areas, eliminating
the need for operator intervention when transitioning from one beacon coverage zone
to another.
When desired, you may also tune the beacon receiver manually by using the menu
system. This is discussed in Section 4.12.2.
2.4.1.2 ABS Global Beacon Search
When powered for the first time in ABS mode, the RX 400p initiates a Global Search
using, examining each available DGPS beacon frequency, and recording Signal
Strength (SS) measurements in units of dB
µV/m to the Global Search Table. The
receiver uses these measured values to compute an average SS, and noise floor, to
sort the frequencies in descending order of SS. The beacon receiver’s two channels
cooperatively examine the frequencies with the highest SS measurements, above the
computed noise floor, to determine the station providing the strongest RTCM signal.
The receiver's primary channel locks to the first identified DGPS broadcast, while the
second channel continues searching in the background for superior beacon signals. If
no signal is available, the RX 400p will initiate a fresh Global Search, continuing this
cycle until it finds a valid station.
2.4.1.3 ABS Background Beacon Search
During the Background Search, the second beacon channel examines all frequencies
at both 100 and 200 bps MSK bit rates to identify beacons possessing superior signal
quality. If a DGPS broadcast is identified that exhibits a 2 dB greater signal strength
than that of the primary station, the receiver will automatically switch to this beacon.
No loss of lock occurs on the primary station during the background scan.