Specifications

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WARNING: Disconnect primary power prior to servicing.
COFDM (Coded Orthogonal Frequency Division Multiplex):
A transmission technique in which the information content of a complete ensemble
(multiplex) is divided and modulated onto a multitude of closely neighboring RF
carriers within a channel bandwidth (frequency block). The division of the
information payload among a large number of RF carriers ensures that each
individual RF carrier has a very low data rate (symbol rate). The long symbol period
of the individual RF carriers allows the receiver to wait until all delayed signal
reflections have arrived and been added to the direct signal (...during a guard
interval to be discarded). This permits recovery a stable signal in difficult reception
conditions, especially during mobile reception.
CRC (Cyclic Redundancy Checksum):
A procedure for error detection in digital signals. Before distribution to the
transmitter, a CRC is computed for the transport stream signal. This CRC is sent in
the transport stream. Upon reception at the transmitter site, another CRC is
computed from the received transport stream and compared to the transmitted value.
If the CRCs are identical, no error has occurred during the distribution to the
transmitter site.
DAB Mode (Digital Audio Broadcast):
A digital radio/multimedia standard for transmitting multiple programs within a 1.5
MHz RF frequency block. The original DAB standard has been extended by two
different enhancements to the encoding layer: DAB-Plus and DMB. All three
standards use the original DAB modulation format in the transmitter (changes are
upstream in the encoder). Four different DAB modes exist. All VAX transmitters
use DAB mode I.
DAC (Digital Analog Converter):
A circuit that converts digital values inside the processing stages of the LPU
modulator into analog RF waveforms for amplification and transmission by the
transmitter.
dBm (Decibels over 1 milliwatt):
A logarithmic signal power measurement scale referenced to 1 mW. 0 dBm is
equivalent to 1 mW. 10dBm = 10mW, 20dBm = 100mW, 30dBm = 1000mW.
DMB (Digital Multimedia Broadcasting):
A modification of the basic DAB system according to ETSI standard (TS 102 427
and TS 102 428) using MPEG-4 (H.264) and BSAC/HE-AAC V2 compression to