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Chapter 5. Balanced Hybrid / Balance Transformer
5.1 Description
The balanced hybrid can be used to connect two
transmitters or a transmitter and receiver together,
although usually a skewed hybrid is used to
connect a transmitter and receiver together. The
back plate contains 3 female BNC connectors (IN
1, IN 2, and Line) which are the only connections
that need to be made to the hybrid. If desired, a
male BNC to female UHF adapter accessory is
available for changing the output connector to
UHF (See Chapter 1). A gas tube protector is also
located across the Line coax connector to limit
surge energy coming into the hybrid.
A balance transformer is just the same as a
balanced hybrid operated in the reverse direction.
The 2 inputs become 2 outputs and the one output
becomes an input. The front & rear labels are
different than the balanced hybrid as a result. Also
the board's chassis location is fixed due to the
special front label needed for it. It is typcally used
for phase-to-phase coupling applications.
5.2 Customer Interface Points
5.2.1 Jumpers
• JMP1 (Line Z) = 50 or 75 Ω.
Shipped setting = 50 Ω.
JMP1 is used for setting the output impedance of
the line port which is generally 50 Ω in the USA.
• JMP2 = Switch Enable or Disable.
Shipped setting = SW Enable.
JMP2 is used to enable or disable the front push-
button switch. For customers not desiring the
switch, it gives them a way of jumpering it out of
the circuit.
5.2.2 Test Points for Balanced Hybrid
(Black)
• Input 1 – For IN1 Coax connector
• Input 2 – For IN2 Coax connector
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• Common – This is the common for all the
test points
• Output – This is the Test Point before the in-
line pushbutton switch
• Line – This is the Test Point after the in-line
pushbutton switch. Electrically tied to the
Output Test Point unless the pushbutton
switch is pressed
5.2.3 Test Points for Balance
Transformer (Black)
• Output 1 – For OUT1 Coax connector
• Output 2 – For OUT2 Coax connector
• Common – This is the common for all the
test points
• Input – This is the Test Point before the in-
line pushbutton switch
• Line – This is the Test Point after the in-line
pushbutton switch. Electrically tied to the
Input Test Point unless the pushbutton
switch is pressed
5.2.4 Pushbutton Switch
NOTE: The pushbutton switch is recessed to
prevent accidental activation. Use a narrow tool
such as a pocket screwdriver to press it.
SW1 – This is a normally closed front panel push-
button switch that allows for an in-line reflected
power meter to be inserted between the Output
and Line test points when pressing this switch.
When using this switch, the in-line meter is
always inserted into the test points first, and then
the pushbutton is pressed for the measurement and
released before removing the meter.
This prevents loss of the carrier signal when
inserting the meter, therefore, there is no need to
take the system out of service when properly using
this switch.
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