Users manual
N4430-O-G
Revision #:
B
Date:
8-23-18
Page
13
of
74
5.0 Built-in Test
There are a number of power supplies in the design to meet special needs and
noise reduction. Each supply is monitored and a power failure will be indicated by
the status pin dropping to 0V. The NMEA output $GPNVS can also be monitored
for power /-5V, Antenna current, Output Vrms, etc.
6.0 Power
The standard unit is designed to operate from a nominal 5 VDC ±0.1 volts. During
turn on, the OCXO draws considerable current and the maximum current will
approach 1000ma. After the OCXO has stabilized, the current will be in the 200 to
500ma range depending upon temperature. Any noise on the power supply will
compromise phase noise performance. The power should be heavily filtered and
decoupled at the connector.
7.0 GNSS Function
The receiver needs to be able to see at least four satellite vehicles (SVs) to obtain
an accurate 3-D position fix. When travelling in a valley or built-up area, or under
heavy tree cover, you will experience difficulty acquiring and maintaining a coherent
satellite lock. Complete satellite lock may be lost or only enough satellites (3)
tracked to be able to compute a 2-D position fix, or a poor 3-D fix due to insufficient
satellite geometry (i.e. poor DOP). Inside a building or beneath a bridge, it may not
be possible to update a position fix. The receiver can operate in 2-D mode if it goes
down to seeing only 3 satellites by assuming its height remains constant. But this
assumption can lead to very large errors, especially when a change in height does
occur. A 2-
D position fix is not considered a good or accurate fix; it is simply “better
than nothing”.
The receiver’s antenna must have a clear view of the sky to acquire satellite lock.
Remember, it is the location of the antenna that will be given as the position fix. If
the antenna is mounted on a vehicle, survey pole or backpack, allowance for this
must be made when using the solution.
