DSNG uplink types
An SNG uplink system consists of the following primary component parts:
• antenna with mounting support
• high power amplifier(s) (HPA)
• upconverter
• modulator
• signal monitoring
• baseband signal processing.
The physical transmission components of an uplink are typically referred to collectively as the chain or thread. A chain typically consists of a single transmission path that has one of each of the primary transmission components – digital encoder, modulator, upconverter and an HPA.
An SNG system may have some or all of its constituent components duplicated – two or more chains can be combined to feed via a single antenna, using a phase-combiner.
This may be to give a degree of redundancy and provide immediate back-up in the event of failure, or an extra HPA may be added to increase the uplink power (not usual in digital systems).
It may be that the system has to provide more than one transmission path where there is a requirement to uplink more than one programme signal simultaneously, combining two programme signals into a single signal applied to the antenna. A single transmission chain could also achieve this by using cascaded digital encoders.
There are several different configurations that can be used, but no matter what the configuration, in news operations the factors of speed and reliability are significant issues, and the component parts have to be rugged, reliable and quick to set up in operation.
However, as might be guessed from what has already been said, a system can be configured in a variety of ways. The characteristics of an SNG system are defined by:
• type of packaging – e.g. vehicle or flyaway
• frequency band of operation – C- or Ku-Band
• level of redundancy – none, partial or full
• number of paths – one, two or more.
By their very nature, SNG systems are not permanently fixed as the essential requirement is to be able to move quickly and operate in response to a breaking news story.
SNG systems therefore have to be packaged in a way that allows them to be easily transported and then rapidly set up on location.
Configuration
Systems are constructed in either one of the following ways:
• Flyaways – As indicated by the term, flyaway systems are designed to be broken down to fit into a number of equipment cases for easy transportation by air and then reassembled on location.
• Vehicle based – the SNG uplink is typically built into a vehicle (a van or a truck) as a permanent installation. The system can then be driven to location and quickly put into operation.