Hubbel RFL PLC Hybrid Pro, Руководство пользователя

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RF-MCHYBRIDPRO-01
Hubbell Power Systems, Inc. – RFL™ Products
June 2019 11 973.334.3100
hybrid is fed into the TX port on the skewed hybrid. Instead of coupling just one transmitter, a skewed
hybrid can pass multiple transmit signals, so long as they are combined with balanced hybrids first.
Note that in this configuration there are also two receivers, but they do not need to be combined with a
hybrid, as is the case for the transmitters. Because receivers are highly selective and are high-
impedance devices, they can be directly paralleled and will not load or otherwise interfere with each
other. Some receivers have an option to provide a termination in the form of a non-inductive resistor
equal to the desired termination value (usually 50 ohms). This option should only be used when no
hybrid is used, for example a single Rx-only device that connects directly to the line tuner. When more
than one receiver is installed, the receivers themselves should be left unterminated. The skewed
hybrid’s RX port provides the required termination for the hybrid circuit. This is an operational
advantage as well – for service and maintenance operations, removing any one receiver from the circuit
will not affect the RX termination value.
F
IGURE
3 could represent several different applications. TX1/RX1 might be DTT and TX2/RX2 might
be DCUB or POTT; or, TX1/RX1 and TX2/RX2 might represent a dual-DTT scheme.
3.3 Three Transmitters, Three Receivers (FSK)
TX1
TX2
BAL
SK
RX1
RX2
to/from Line Tuner
BAL
TX3
RX3
Figure 4 – Three Transmitters, Three Receivers (FSK)
F
IGURE
4 is a further expansion of the system in F
IGURE
3 . This system illustrates how the output of
one balanced hybrid can be an input to another balanced hybrid, to accomplish the coupling of more
than two transmitters in a PLC system. Again, the output of the last balanced hybrid is fed into the TX
port on the skewed hybrid.
The system in
F
IGURE
4 might represent a dual-DTT / DCUB system. Here, it is best to make
TX1/RX1 and TX2/RX2 the DTT channels, so that both will have equal losses, and to make TX3 the
DCUB channel so that DCUB, as the primary protection scheme, has the least loss through the hybrids.