Power Line Carrier Coupling Equipment

RFL offers a wide range of coupling equipment for a complete Power Line Carrier solution. These products include X and Skewed hybrids, High Power Splitters and Combiners, Line Tuners and Line Traps.

Coupling Equipment

Power Line Carrier Coupling Equipment

Jump To: Hybrids (X-Hybrid and Skewed Hybrids) | Splitters/Combiners | Line Tuners | Line Traps

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About Coupling

The necessary isolation of a line section at carrier frequencies used for communication is accomplished using coupling equipment, such as by a line inductor connected in series with the line. It is usually tuned to form a line trap, so that it presents a high impedance over a band of frequencies which may be either narrow or wide.

Separation of the power-frequency energy from the carrier-frequency band is accomplished with the coupling capacitor, and the function of the line-tuning unit is to cancel the reactance of the coupling capacitor to achieve optimum impedance matching and power transfer of the carrier signal to and from the transmission line. The line-tuning unit may also tune out the reactance of the coupling capacitor over either a narrow or a wide band of frequencies.

10 Watt Hybrids

Hybrids are optional modules for the RFL Power Line Carrier equipment. They may be used to combine combinations of transmitters and receivers to a single port for connection to line tuning units. There is an X-Hybrid Module and a Skewed Hybrid Module available.

An Auxiliary Hybrid Chassis is used to add X-Hybrid modules or Skewed Hybrid modules to RFL Power Line Carrier systems. Each Auxiliary Hybrid occupies one rack unit (1RU) of space in a standard 19” rack. Each chassis can accommodate three Hybrid modules and three Hybrid I/O modules. In a given chassis the Hybrid modules can be a mix of any combination of X-Hybrid modules or Skewed Hybrid modules.

X-Hybrid – The X-Hybrid Module is a transformer-type hybrid typically used to combine the outputs of two transmitters. The X-Hybrid provides the required impedance matching and signal separation, and prevents mutual loading of the two transmitters.


  • Insertion Loss: Approximately 3.5 dB, either input port to line output port.
  • Trans-hybrid Loss: Greater than 25 dB, from 60 to 500 kHz, when operating with the specified terminations impedances.
  • Power Capacity: 10 Watts RMS.
  • Two-Wire Line Impedance: 50 or 75 Ohms.
  • Second Harmonic Distortion: At least 80 dB below the fundamental frequency.
  • Third Order Intermodulation Products: At least 60 dB below the fundamental frequency.

Skewed Hybrid – The Skewed Hybrid Module uses two hybrid transformers to connect a transmitter and receiver to a single line tuning port. The Skewed Hybrid provides a high degree of signal separation by isolating the local transmitter signal from the local received signal and preventing the input impedance of the receiver from loading the transmitter.


  • Insertion Loss:
    • Transmitting: Approximately 0.3 dB
    • Receiving: Approximately 12.5 dB
  • Trans-hybrid Loss: Greater than 40 dB, from 60 to 500 kHz, when operating with the specified terminations impedances.
  • Internal Balance Range: 0.5 to 1.95 times the specified two-wire impedance.
  • Power Capacity: 10 Watts RMS.
  • Two-Wire Line Impedance: 50 or 75 Ohms.
  • Second Harmonic Distortion: At least 80 dB below the fundamental frequency.
  • Third Order Intermodulation Products: At least 60 dB below the fundamental frequency.

Contact RFL for more information.

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Splitters & Combiners

Splitters and Combiners are Power Line Carrier Hybrid assemblies for special applications. These applications include High Power, Dual Phase and Mode 1 Combining. RFL custom makes Power Line Carrier Splitter and Combiners for your application.

Contact RFL for more information.

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Line Tuners

Line-tuning units, like the trap, may be resonant with the coupling capacitor at either one or two specific frequencies, or across a broad band of carrier frequencies. Frequently, the coupling capacitor and line-tuning unit form a highpass filter. The filtering required is very simple, but the tuning unit will have to pass carrier signals at powers up to 100 watts, and must usually be equipped with a drain coil, surge protector, safety shorting switch, etc. The tuning unit is normally located close to the coupling capacitor in the switchyard, and must be weatherproof. For phase-to-phase coupling, it's common to employ two line-tuning units, driven by a suitable push-pull transformer.

The RFL ® 9512 Line Tuner matches the impedance of the Power Line Carrier (PLC) terminal to the high voltage power line in order to reduce the insertion loss of the transmission of PLC signals over the power line. In addition, isolation from the power frequency voltage and transient overvoltage protection is provided.

The RFL ® 9512 Line Tuner is available for Phase-To-Ground or Phase-To-Phase Coupling.

Download Brochure (PDF)

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Line Traps

Line Traps, also known as Wave Traps, are a critical part of Power Line Carrier communications.

A line trap is a large inductor, capable of continuously handling high values of power-frequency current, and rugged enough to withstand the stresses of higher current surges. It ranges in inductance from about 0.265 mH to about 3 mH. While large inductances are very expensive, smaller values do not normally have sufficient reactance to decouple adequately at lower PLC frequencies; so it is common practice to tune the line inductor with a tuning pack, which may form a resonant trap at one or two specific frequencies for narrow channels, or which may present an impedance of 400 to 600 ohms over a broad band of PLC frequencies. While narrowband traps are largely reactive, broadband traps are largely resistive within the resonant band, and thus they provide assurance against unwanted resonance with unpredictable reactance of the station bus or other line section.

Contact RFL for more information on line traps.

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