ShortHaul Control Station Combiners

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RFI’s ShortHaul Control Station Combiner (SHCSC) is an ideal solution for combining multiple radios in Control and Dispatch Centers, or in other short-distance point-to-point link applications. SHCSCs provide guaranteed RF isolation performance between each of their ports, allowing predictable protection levels to be achieved between all of the radio equipment connected to it. The ability for multiple radios to co-locate at an installation is important in busy Control and Dispatch room applications, where interference (intermodulation, desensitization or blocking) can degrade communications quality and reliability as radio traffic and channel usage increases – particularly during incidents and other peak workload times. The innovative design of the SHCSC allows both single antenna port (half duplex) and dual antenna port (full duplex) radio equipment to be connected to it – combining the different types of equipment together. The use of SHCSCs reduces the number of rooftop antennas (and associated coaxial feeder cables) that are required in a multiple-radio installations – reducing tower or building rooftop loading, installation effort, materials and associated costs. This reduction of installation materials can also improve a rooftop’s appearance by reducing the cluttered look of multiple antenna installations, which can assist in the granting of building and development approvals and permits.


A ShortHaul Control Station Combiner (SHCSC) is an innovative combiner technology that can combine multiple control and dispatch center operators’ radios, or multiple point-to-point link radios, into a single antenna. The inherent design architecture of the SHCSC provides guaranteed isolation between all of the radio equipment units connected to it, irrespective of the individual ‘transmit’ or ‘receive’ mode of operation, ensuring RF interference problems do not occur between the units and that their communications quality and reliability is not compromised.

SHCSCs provide the following features:

  • Broadband operation (40-960MHz)
  • Available in capacities from 4 to >128 ports
  • Compact size. Easily installed and relocated
  • Convenient plug’n’play field expandability
  • Centralized or Distributed architectures
  • Manages multiple radios’ co-location issues
  • Minimizes tower and building rooftop loading
  • Reduces site installation costs and effort

SHCSCs provide a flexible combining solution across their entire broadband frequency range. This capability is particularly useful in multiple frequency systems, such as trunked radio or voting systems, where the specific frequency of operation for each operator’s radio can vary on a call-by-call basis, or in applications where a control and dispatch center may be coordinating communications across multiple networks and or frequency bands (i.e. VHF, UHF and or 7/8/900MHz). SHCSCs are also ideally suited for combining the emerging range of multi-band mobile radios.

Control and Dispatch Center Combining

Control rooms often co-locate multiple ‘control stations’ (usually desk-mounted or VOIP/ROIP remotely-connected mobile radios), allowing radio despatchers or operators to communicate with multiple field-based personnel simultaneously.

Depending on the radio system frequencies in use, the simultaneous operation of these multiple control stations can experience co-location interference problems – such as intermodulation, desensitization and blocking – that can degrade the quality and reliability of their communications. This can be particularly true where multi-channel trunked radio systems are being utilized and the actual radio channel frequencies allocated for each call at each control station changes randomly on a call-by-call basis.

Such co-location interference problems can be unacceptable – particularly in operations and mission critical applications, and the SHCSC can be used to assist in managing these issues in both small and large control room installations.

Short-Haul Multi-Channel RF Link Combining

At many communications sites, multiple RF point-to-point and point-to-multipoint links may be deployed as part of the various systems installed at the site. In many applications, such as open cut mines, processing plants, and military and major infrastructure installations, multiple communications sites may be used to provide extensive coverage within a relatively small area. In such situations, and where multiple links are being operated between these sites, a SHCSC can be used to reduce the number of individual antennas and feeder cables required at the site. This can reduce equipment installation cost and effort, reduce tower or building rooftop loading and clutter, and better manage the intra-system RF isolation between these multiple links and their associated RF equipment.

Single Port or Multi-Port Capability

The SHCSC can be used with both single port (half-duplex) and dual port (full-duplex) RF equipment. The guaranteed isolation provided between ports in the SHCSC design provides the flexibility for these different equipment types to be combined to suit a diverse range of wireless technologies and their applications.

Broadband and Multi-Band Operation

The SHCSC’s innovative design provides broadband operation across 40MHz to 960MHz. This broadband capability suits multi-band operation, and the use of SHCSCs in these multi-band applications allows the rationalizing of coaxial cables in these systems – reducing installation time and costs, and minimizing tower and building rooftop loading and clutter. RFI also offers a comprehensive range of crossband couplers, antennas, and other accessories to support multi-band applications.

Combiner Installation, Capacity, and Expandability

The combining of multiple radios can now be realized in a compact 19inch rack mount footprint. SHCSCs can also be installed directly into ceilings, onto furniture, or in other locations such as beneath stairs, inside cupboards, or into other spaces that may be available in control rooms and dispatch centers, equipment rooms or communications sites where the installation of these combiners may be planned.

SHCSCs are available using 4 and 8 port model decks. An 8 port model with an Expansion Port, and a 4 port Expansion Deck is also available to enable the creation of multiple SHCSC configurations catering for various port capacities and expansion capabilities.

SHCSC Insertion Loss

The design architecture featured in a SHCSC is often perceived as having higher-than-desirable insertion loss. However, in short distance applications, the off-air received signal level from high-powered communications site base stations can be quite high. Reducing these high levels through the SHCSCs insertion loss results in acceptably lower RF signal levels being presented to the associated RF equipments’ receivers – preventing potential RF overloading (blocking), and preventing non-linear mixing and the generation of intermodulation products in the receiver front end circuitry.

Conversely, the RF output power of the control station or link radio’s transmitters could present the associated receiving equipment with unacceptably high RF signal levels – which could cause similar receiver performance problems in the other communications path direction. The SHCSC’s insertion loss also assists in reducing such RF signal levels within acceptable levels for the equipment.

RF link path modelling, using the transmit powers, cable losses, antenna gains, propagation path losses, receiver sensitivities and desired performance margins can quickly establish if a SHCSC (or perhaps another combiner type – such as the ‘standard’ Control Station Combiner) is suitable for use for the specific application or installation scenario.


Multiple Control Station Dispatch Center

The multiple despatcher mobile radios (control stations) in a busy control center can be combined using a SHCSC. The SHCSC provides predictable isolation between all connected radios, irrespective of their transmit or receive operating state, facilitating the co-location and interference-free operation of these units. The quality and reliability of communications in busy operations-critical or mission-critical despatcher environments, particularly during the periods of congested communications when managing major incidents, can be protected and provided using SHCSC combiners.

Multiple VOIP/ROIP Operator Consoles

In VOIP/ROIP console installations, despatcher consoles may be connected to remote mobile radios (control stations) or link radios. At the control stations’ or link radios’ location, a Short Haul Control Station Combiner (SHCSC) may be used to provide the required RF isolation between the units to ensure their interference-free operation from each other. The benefits of the rationalization of coaxial feeder cables and antennas can also be realized.

Distributed Installation Architecture

A SHCSC combiner of any capacity can be centrally located and the various items of radio equipment can be cabled to it as desired. However, if radio equipment is located in separate locations (i.e. clustered in furniture pods or in different rooms) then SHCSC’s may be used to combine each cluster, with the output of each SHCSC then cabled to a centralized SHCSC expansion deck which combines the multiple equipment clusters for connection to the one shared antenna. This de-centralized installation approach reduces the overall cabling clutter in cable trays and reduces total installation effort and costs.

Control Room Back-Up Communications

A busy console-connected dispatch center may utilize mobile radios (control stations) as a method of communications back-up. In these applications, mobile radios are often installed at despatchers’ desks, with coaxial cabling and a multiple rooftop antennas installed pointing towards communications network sites. In the event of console system or IT communications link failures, these mobile radios are used to continue dispatch operations. Installing multiple mobile radios in close proximity to each other often results in interference between units, reducing communications reliability and quality. The use of Short Haul Control Station Combiners can ensure the required levels of RF isolation between these mobile radios is provided, mitigating these interference problems commonly experienced in these scenarios.

Event & Short Term Rental Radio

Many sporting and other events use a management control or dispatch center as part of their activities. Examples of these may be Race Control or Pit Crews at a car or motorcycle race event, an announcer or event organizer at a music or other community festival. In these scenarios, 2way rental radio providers often deploy transportable short-term communications solutions, with two-way radio network repeaters located in close proximity to the management control center and required event radio coverage area. The SHCSC provides a compact, cost effective, conveniently deployable, and frequency-independent solution for these users. The SHCSC particularly suits these types of applications, where the operating frequencies may vary on an event-by-event basis, depending on network capacity requirements and the resulting number of channels, and their deployed location, and frequency availability at that location.

Multiple RF Links

In some communications scenarios, such as telemetry/scada and broadcasting studio links, multiple RF links may be installed between sites. In such situations, a SHCSC may be used to provide intra-link RF isolation at each equipment site, and to rationalize the coaxial feeder cables and antennas that would otherwise be installed ‘in parallel’ on the sites. This rationalization of installation materials has the added benefit of reducing cabling and cable tray congestion, weight and wind loading impacts on building rooftops and towers, and in reducing initial installation and ongoing maintenance costs.

Reducing Equipment, Rooftop and Tower Congestion

The use of SHCSC allows multiple wireless communications equipment items to be combined together, sharing coaxial feeder cables and antenna systems. This rationalizing of cabling, antennas, and antenna mounting hardware can significantly reduce cable tray congestion, weight and wind loading impacts on building rooftops and towers, and the reduction in the quantity of installation materials also reduces installation labor time and materials costs. In development-sensitive locations, reducing the number of visible cables and antennas can reduce the installation’s environmental impact, and potentially assisting the granting of development approvals and construction permits.

Multi-Band Operation

SHCSCs are capable of operation across a wide range of operating frequencies. In applications where a wide range of operating frequencies may be required, such as dispatch centers communication on multiple radio networks, this capability allows simplified design and installation of such systems to be realized.

In addition, the SHCSC’s operation across a wide range of operating frequencies also supports the emerging availability of dual, triple and quad band mobile radios – and their deployment and use in multi-band multi-network dispatch applications. RFI has a range of Crossband Couplers, Filtering and other accessories available for these designs.


  • Broadband 40-960MHz operation enables the use of a SHCSC across an entire frequency band or multiple frequency bands and supports the use of multi-band mobile radios.
  • SHCSC models are available to suit a wide range of connection capacity requirements. Connection port capacities between 4 and 128 (or more) can be configured using the SHCSC product’s convenient and easy to use “building block” architecture.
  • The SHCSC’s compact size and weight reduces installation space requirements, A 4 or 8 port unit only requires 1RU of 19inch rack space – or SHCSC’s can be mounted directly onto walls, in ceiling spaces, inside consoles, behind furniture, or into many other available installation locations.
  • SHCSC models with expansion ports and Headend units are also available to combine multiple layers of SHCSC architecture. Expansions of SHCSC combiners can be easily and conveniently carried out in the field – allowing these combiners to be expanded or re-configured to keep pace with customers’ changing needs.
  • Centralized or De-Centralized installation architectures can be used to optimize the SHCSC installation within a control or dispatch room, equipment room, or other location. The ability to distribute the SHCSC combiner across multiple locations (rooms, floor or buildings) allows cabling to be rationalized and installation time and cost to be minimized.
  • The guaranteed port-to-port isolation and insertion loss performance of the SHCSC allows the potential problems of co-locating multiple units of RF equipment in a small area to be managed. When not managed, these problems can cause interference (Intermodulation, desensitization or blocking) between units, that can degrade communications quality and reliability as radio traffic and channel usage increases – particularly during incidents and other peak workload times.
  • The ability of a SHCSC to combine multiple control stations or link radios to a single antenna can significantly reduce the number of antennas and associated coaxial feeder cables on a tower or building rooftop – also reducing the structure’s loading and clutter, and making an installation less visually impacting – particularly in sensitive development approval and permit locations. Such a reduced installation is also more convenient and cost effective to reconfigure, remove or re-locate in the future if required.