MD-1142/UGC Modem Time Diversity BR Communications 6029C Time Diversity Modem

Description: BR Communications, which later merged with TCI to become TCI/BR and was subsequently acquired by Dielectric Inc., produces a series of chirp sounder transmitters and receivers. One notable feature of the Chirp Sounder system is the narrow shift order wire signal that is superimposed on a carrier frequency that sweeps from 2 to typically 30 MHz. This short order wire message has a very high probability of being received globally. BR Communications also developed a line of HF radio modems aimed at achieving a similar high reliability in contact communications. The MD-1142, also known as BR 6029C, operates in two modes, both of which are full duplex (the receiver and transmitter sections are fully independent). In the Internal Multiplexer Mode, a single TTY signal is distributed to seven different channels, with each channel's signal delayed by one second relative to the others. Additionally, a pilot tone at 561.1 Hz is included, enhancing the probability of successful message transmission. In the External Multiplexer Mode, each of the eight channels receives a separate data stream, lacking the redundancy of the Internal Multiplexer Mode. The manual for this device is 0040-6029-15005 and includes details on installation, operation, theory of operation, maintenance, parts breakdown, and schematics. The construction of the device resembles that of the RCS-5A receiver, featuring a motherboard with plug-in daughterboards for each function.

The BR Communications chirp sounder transmitters and receivers are integral components in high-reliability communication systems. The chirp sounder technology employs a unique modulation technique that allows for effective transmission over a wide frequency range, specifically from 2 to 30 MHz. This capability is particularly advantageous in varying atmospheric conditions, where traditional communication methods may falter.

The MD-1142 (BR 6029C) model exemplifies advanced design in HF radio modems. Its full duplex operation means that it can transmit and receive simultaneously, ensuring seamless communication. The Internal Multiplexer Mode is particularly noteworthy, as it enhances message integrity through time-delay multiplexing. By delaying the signals across multiple channels, the system can mitigate the effects of interference and ensure that at least one of the delayed signals is likely to be received correctly.

The pilot tone at 561.1 Hz serves as a reference signal, aiding in the synchronization of the receiver and improving the overall reliability of the communication link. In contrast, the External Multiplexer Mode provides flexibility by allowing each channel to operate independently. This can be beneficial in scenarios where diverse data streams need to be managed without the redundancy provided by the Internal Multiplexer Mode.

The accompanying manual (0040-6029-15005) serves as a comprehensive resource for users, detailing all aspects of the system's operation and maintenance. It includes schematic diagrams that illustrate the internal architecture, enabling technicians to troubleshoot and repair the device effectively. The modular construction, featuring a motherboard with plug-in daughterboards, simplifies upgrades and maintenance, allowing for easy replacement of individual components without the need for extensive rework. Overall, BR Communications' chirp sounder systems and HF radio modems represent a significant advancement in robust communication technology, suitable for various applications requiring reliable and efficient data transmission.BR Communications (later merged with TCI to become TCI/BR, later bought by Dielectric Inc ) makes a line of chirp sounder transmitters and receivers. See my RCS-5 Chirp Sounder page for more on this. One of the features of the Chirp Sounder system is that a narrow shift order wire signal is superimposed on the carrier that is sweeping up in frequ

ency from 2 to typically 30 MHz. This short order wire message has a very high probability of being received anywhere in the world. I think that BR communications developed a line of HF radio modems to try an offer a similar high reliability of contact communications. The MD-1142 aka BR 6029C has two modes of operation both are full fuplex (the receiver and transmitter sections are fully independent), in the Internal Multiplexer Mode a single TTY signal is fed to 7 different channels and the signal in each channel is time delayed by 1 second form all the other channels.

In addition there is a pilot tone at 561. 1 Hz. This mode of operation provides a high probability of getting the message through. In the External Multiplexer Mode each of the 8 channels is fed or receives a separate data stream so it does not have the redundancy of the IMM. In time order the channels are: The manual is 0040-6029-15005 and contains Installation, Operation, Theory of Operation, Maintenance with parts breakdown and schematics.

The construction is similar to the RCS-5A receiver, that is a mother board with plug in daughter baords for each function.