RFX-RMT-II Dual Band
LAST REV: April 2008
18
Operator’s Manual
RF ExtremeCare: 866.732.0113
7.2 COFDM
Modulator
The normal scheme of COFDM modulation adopted by RF Central for the RMT-II Dual Band
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. 2 GHz). This method reduces the occurrence of inter-modulated harmonic frequencies
and requires less up-conversion.
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 –9 dBm.
When the traffic being carried by the Tx 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 chart in Appendix B
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 LED mentioned in clause 8.2, and also displayed in the
status menu.
To ensure good RF practice, when power is applied to the RMT-II Dual Band, 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.
