RFL Auxiliary Hybrid Chassis
RFL Electronics Inc.
March 29, 2005
8
(973) 334-3100
THEORY OF OPERATION
For this discussion, refer to the schematic diagram shown in Figure 5.
The Skewed Hybrid Module uses two hybrid transformers to couple signals between a transmitter, a
receiver, and a 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 and received signal passes through a 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). This
allows both the transmitter and the receiver to be coupled to the line tuning unit. The other set of
secondaries is connected across the internal balancing network formed by resistors R4 through R11.
The coarse balance switch SW1 and fine balance potentiometer R4 can be adjusted to vary the
resistance across the transformer secondaries, which determines the amount of transhybrid loss.
The transmitter output is connected across the primary of L1, and the receiver input is connected
across the primary of L2. Transmitter output signals are coupled through L1 to the line tuning unit, and
incoming signals detected by the line tuning unit are coupled through L2 to the receiver. Transmitted
signals are attenuated by about 0.3 dB as they pass through the Skewed Hybrid module, and received
signals are attenuated by about 12.5 dB. Because both the received signal and its noise content are
attenuated equally, signal-to-noise ratios are unaffected.
