User`s manual

100-M0056X2B 7 of 28
www.cobham.com/gms
The Broadcast version of the MDL (Messenger Digital Link) provides professional Audio/Video (A/V)
interfaces and processing. All versions of the MDL use a robust digital modulation system known as
Coded Orthogonal Frequency Division Multiplexed (COFDM) that provides frequency diversity and
powerful Forward Error Correction (FEC) algorithms. The MDL provides a robust wireless link that is
effective against the multipath interference experienced by analog systems, and provides crisp, clear
pictures in the most difficult of terrains.
This manual provides information on how to operate the MDT-B as well as pertinent technical
information related to the overall system. Also refer to model identifier (on-line document, 100-
MNI0031) at GMS website, www.gmsinc.com, for available frequency and power configurations along
with available options.
3.1 Key System Features
• SDI, ASI, Component, S-Video & Composite Interfaces
• 4:2:2 and 4:2:0
• Coded Orthogonal Frequency Division Multiplexed (COFDM) Modulation
• Output Frequency 1 to 6 GHz (In-Bands)
• Low System latency (~80ms)
• Built-in MPEG-2 Encoder
• Companion COFDM Receiver with Maximal Ratio Pre-Detect Diversity Reception.
• Rugged and Compact Portable Design
4.0 Theory of Operation
The MDT-B Broadcast version accepts either an ASI (Asynchronous Serial Interface,) SDI (Serial Digital
Interface), Component, S-Video or Composite video signal and embedded audio or analog stereo
audio inputs (mic or line level). The video is compressed (ASI data streams are passed through
bypassing the MPEG encoder) according to MPEG-2 specifications. The MPEG-2 supports 4:2:2 or 4:2:0
chroma sampling, 422P@ML, MP@ML and SP@ML profiles and maintains the original signal’s video
fidelity. The audio is compressed using MPEG Layer II compression. The audio, video and data packet
PES streams are multiplexed with basic service data to indicate the service name and transmitted
across the wireless link.
Additionally, the MDT-B/MDR-B combination employs a specially designed ‘low delay’ coding
technology, which provides an end-to-end latency of approximately 80ms without the introduction of
any further MPEG encoding artifacts. This ensures that the picture you see is what is happening now –
crucial for applications such as sports coverage.
5.0 Getting Started
The standard MDT kit includes the following items:
 MDT-B unit (example GMS p/n MDTF1A0NXXX001)
 MDT-B full breakout cable (GMS p/n 780-C0224)
(Power, A/V, Data, Control interfaces)