RFX-RMT-II SD/HD
LAST REV: DEC 2007
17
Operator’s Manual
RF ExtremeCare: 866.732.0113
7.2 COFDM Modulator
The normal scheme of COFDM modulation adopted by RF Central for the RFX-RMT-II is
2k carriers with selection of 6, 7, 8 MHz RF bandwidth.
The COFDM modulator has been designed to take its input from the MPEG2 encoder, or
from an external ASI. This transport stream is then modulated directly to the output
frequency band (e.g. 2GHz). This method reduces the occurrence of inter-modulated
harmonic frequencies and requires less upconverters
The COFDM modulator RF output is via the SMB connector. This output is then fed, via
the analog / digital RF switch, into the power amplifier. The nominal RF output level from
the Modulator is –9dBm.
When the traffic being carried by the transmitter is video and audio, the modulator is
automatically configured to match the data rate of the MPEG2 Encoder, as defined by
the selected parameter set.
When the traffic being carried by the Tx is ASI, the modulator may be set for
modulation, FEC and guard interval, according to the charts in Appendix C.
There are no field replaceable parts on the COFDM modulator. If a fault occurs with the
board, please contact RF Central for technical assistance.
7.3 Power Amplifier
The function of the power amplifier is to amplify the signal from the COFDM modulator to a
suitable level for transmission. The amplifier is required to be highly linear to
accommodate the high order modulation modes employed for digital system operation,
with very low distortion (low inter-modulation between carriers). The nominal output power
is +27dBm (500mW) (band specific).
The status of the PA is shown by the LED mentioned in Section 8.2, and also displayed in
the status menu.
To ensure good RF practice, when power is applied to the RMT-II, always make sure that
there is a suitable load or antenna connected to the RF output.
There are no field replaceable parts in the power amplifier. If a fault occurs with this
module, please contact RF Central for technical assistance.
