RFL 9780 RFL Electronics Inc.
September 8, 2001 18-3 (973) 334-3100
18.2.2 THEORY OF OPERATION
For this discussion, refer to the schematic diagram shown in Figure 18-4.
The X-Hybrid module is a transformer-type hybrid used to connect a transmitter and a receiver, or two
receivers, to a single line tuning unit. It provides impedance matching and signal separation, and prevents
mutual loading and interference. Signals can be accepted from an amplifier with a source impedance of 50
Ohms with up to 10 Watts of output power.
The transmitted signals pass through a transformer hybrid formed from transformers L1 and L2. These
transformers each have two secondaries, interconnected so that the first secondary of one transformer is
in series with the second secondary of the other. One set of interconnected secondaries is connected to
the line tuning unit through edge connector A24/C24 (high) and A25/C25 (low). The other set of
secondaries is connected across balancing resistors R13/R14 which determine the amount of isolation
between four-wire ports. If additional isolation is required, R13 and R14 can be removed and replaced
with an external balancing network connected across edge connector terminals A18/C18 and A19/C19.
The X hybrid can also be used to connect two transmitters to the same line tuning unit, resulting in dual-
channel transmission capabilities. In this application, one transmitter is connected across the primary of L1 ,
and the other transmitter is connected across the primary of L2.
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