28 / 32
User Manual
Rev. 1.0 - 20/06/08
PJ500C-LCD, PJ700C-LCD & PJ1000light
A directional coupler is provided at filter output to measure forward and reflected
RF output power; power readings are relayed to the Interface and Bias boards to
enable processing and display.
The LPF board incorporates an RF output (having a level about -60 dB lower than
output level) which is brought to a BNC connector (figure 6.2). This provides a
convenient test point to check carrier characteristics,
but does not ensure an
accurate assessment of higher harmonics
.
8.7 BIAS board (SLBIAS1K3U-2)
The main purpose of this board is to control and correct the bias voltage of the RF
amplification section MOSFETs.
It also provides a measure of the total current absorbed by the RF modules and
incorporates a dedicated circuit for power supply fault reporting.
Under normal conditions, bias voltage is adjusted according to set output power
using feedback based on actual output power reading (AGC).
Abnormal conditions affecting bias voltage so as to trigger foldback current limiting
are:
- Exceeding reflected power at output
- External AGC signals (Ext. AGC FWD, Ext. AGC RFL)
- Temperature too high
- Any one RF module drawing too much current.
8.8 External Telemetry Interface Board (SLTLMTXLCD03)
This board provides an I/O interface for the CPU with the outside environment.
All available machine input and output signals are brought to the REMOTE DB15
connector (chap. 6.3.4).
Also mounted on this board is the INTERLOCK IN BNC connector (figure 6.2)
which can disable device power output. When the central pin is closed to ground,
output power is limited to zero until ground connection is removed.
The INTERLOCK OUT BNC connector (figure 6.2), when used in combination
with an R.V.R. amplifier, is connected to the exciter REMOTE or INTERLOCK IN
connectors using a BNC-BNC connector. In the event of an amplifier fault, the
central conductor is connected to ground and the transmitter is placed into forced
standby mode.
