34 iDirect Satellite Router Installation and Commissioning Guide
iDX Release 3.3
Peaking the Antenna
7.3.1 PWM
When peaking the antenna, Satellite Routers (except the e850mp) generate a pulse train on
the TX Out port. The duration of each pulse is proportional to the received signal strength.
The method is known as Pulse Width Modulation (PWM). Pulses of differing duration are
detected as different voltages by a DC voltmeter.
Ta b l e 3 depicts the range of the PWM voltage output and the as
sociated signal status. When
peaking, the antenna is adjusted for maximum DC voltage
as indicated by a DC voltmeter.
A reading of less than 2 Volts indicates that the signal level is below the detection threshold
of the Satellite R
outer. When a signal at the correct frequency is detected, the PWM voltage
increases sharply to between 2 and 10 Volts. After downstream carrier lock is achieved, the
PWM voltage switches into the 12 to 20 Volt range. PWM voltages in this range increase
linearly with increasing signal strength.
Note: A reading of 12 Volts or greater cannot be obt
a
ined unless the Satellite Router
is locked to the correct spacecraft and network.
When power is applied to the Satellite Ro
uter, BUC power is available on the TX Out port
immediately after power-on self-test (POST) has completed. To disable the BUC power supply
and enable the PWM output, follow the steps in Section 7.4, "Peaking the Antenna".
7.3.2 Histogram
The iSite Antenna Pointing window provides a graphic representation of received signal
strength over time. It provides a voltage amplitude display similar to an oscilloscope,
displaying color-coded traces corresponding to the three voltage ranges shown in Ta b l e 3 .
Starting the histogram automatically disables BUC power
and enables the PWM voltage
output. Both the PWM voltage and the histogram display are used to peak the antenna.
The Antenna Po
inting window provides a Current Signal Strength field that also indicates the
peaking voltage. The reading may differ slightly from that indicated by the voltmeter, but is
used for the same purpose.
7.4 Peaking the Antenna
Execute the procedures in the following sections to achieve peak received signal strength of
the downstream link.
Note: If the Antenna Pointing Histogram does not operate as
expected, refer to “PC
Firewall” on page4.
Table 3. PWM Voltage Ranges and Signal Status
Volts DC Signal Status
0 - 2 Not in pointing mode, hardware problem, or off satellite
2 - 10 Detecting RF energy, but not locked
on the downstream carrier
12 - 20 Locked on the downstream carrier
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