ANSI/SCTE 68-2008 Drop Passives: Matching Transformers 75Ω to 300Ω

ENGINEERING COMMITTEE
Interface Practices Subcommittee
AMERICAN NATIONAL STANDARD
ANSI/SCTE 68 2008
Drop Passives:
Matching Transformers
75to 300
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NOTICE
The Society of Cable Telecommunications Engineers (SCTE) Standards are intended to serve the
public interest by providing specifications, test methods and procedures that promote uniformity
of product, interchangeability and ultimately the long term reliability of broadband
communications facilities. These documents shall not in any way preclude any member or nonmember
of SCTE from manufacturing or selling products not conforming to such documents, nor
shall the existence of such standards preclude their voluntary use by those other than SCTE
members, whether used domestically or internationally.
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Such adopting party assumes all risks associated with adoption of these Standards, and accepts
full responsibility for any damage and/or claims arising from the adoption of such Standards.
Attention is called to the possibility that implementation of this standard may require the use of
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Patent holders who believe that they hold patents which are essential to the implementation of
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© Society of Cable Telecommunications Engineers, Inc. 2008
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TABLE OF CONTENTS
1.0 SCOPE .........................................................................................................1
2.0 MECHANICAL ...........................................................................................1
3.0 ELECTRICAL .............................................................................................1
4.0 ENVIRONMENTAL ...................................................................................2
5.0 NORMATIVE REFERENCES....................................................................2
1
Maximum Insertion Loss (dB)
Frequency Range (MHz) Insertion Loss (dB)
50 - 108 2.0
109 - 300 3.0
301 - 1002 4.0
1.0 SCOPE
The purpose of this document is to specify recommended mechanical and electrical
standards for broadband radio frequency (RF) devices whose primary purpose is to provide
impedance and connector match between 75 coaxial type F and 300 twin-lead open
screw connectorized devices. The most common use for such devices is matching coaxial
input cables from distribution systems to 300 balanced screw antenna terminals on indoor
receivers.
The specification is not intended to limit or restrict any manufacturer’s innovation and
improvement. The specification may be amended in the future as deemed appropriate.
2.0 MECHANICAL
2.1 RF Ports
2.1.1 All coaxial RF ports shall be type F. Female ports shall conform to the
requirements of ANSI/SCTE 01 2006 while male ports shall conform to the
requirements of ANSI/SCTE 123 2006.
2.1.2 300 ports shall either consist of a pair of screw terminals or a short length of
twin-lead cable terminated in a pair of spade lugs.
2.2 Labeling
No labeling is required for either input or output port.
3.0 ELECTRICAL
3.1 Bandwidth. All devices shall be designed to operate over a bandwidth of at least 5 to
1002 MHz.
3.2 Pass-band Response. The pass-band response of two devices connected back-to-back
via their 300 ports, and measured from one 75 port to the other 75port shall not
exceed ±1.0 dB relative to the slope loss of the device as measured and defined in
ANSI/SCTE 144 2007.
3.3 Insertion Loss. The insertion loss of two devices connected back-to-back as described
in Section 3.2 shall not exceed the values specified in the following table. All
measurements shall be made using the methods specified in ANSI/SCTE 144 2007:
2
Minimum Balance (dB)
Frequency Range (MHz) Balance Ratio (dB)
50 35
51 - 300 25
301 - 1002 20
3.4 Return Loss. The return loss shall be measured using a 1%, 300-Ohm resistor
soldered across the 300-Ohm twin-lead cable. The resistor shall be cut to a length
equal to the twin lead conductors. For screw type devices, resistors should be installed
across screw terminals as closely as possible with excess lead material trimmed off.
For threaded twin lead devices, resistors should be soldered across the terminals such
that the terminals remain parallel as originally manufactured with excess lead material
trimmed off. Measuring is accordance with ANSI/SCTE 144 2007, the return loss
shall be no less than 20dB across the pass-band.
3.5 Surge Withstand. The surge protection of the device when measured in accordance
with ANSI/SCTE 81 2007 shall be a minimum of compliance with IEEE C62.41-
1991 Category A-3 Ring Wave 1kV, 200 Amps at the “F” port.
3.6 Balance Ratio. The balance ratio of the transformer, when tested in accordance to
ANSI/SCTE 120 2006, shall not be less than as follows:
-5
4.0 ENVIRONMENTAL
Temperature/Humidity. The matching transformer must meet all specifications when
operated in an ambient temperature ranging from +32°F (0°C) to +122° F (+50° C) and
relative humidity ranging from 5 % and 99%, non-condensing.
5.0 NORMATIVE REFERENCES
The following documents contain provisions that, through reference in this text, constitute
provisions of this standard. At the time of publication, the editions indicated were valid.
All standards are subject to revision, and parties to agreement based on this standard are
encouraged to investigate the possibility of applying the most recent edition of the
documents listed below.
1. ANSI/SCTE 01 2006: Specification for “F” Port, Female, Outdoor
2. ANSI/SCTE 81 2007: Surge Withstand Test Procedure
3. IEEE C62.41-1991: IEEE Recommended Practice for Surge Voltages in Low-Voltage AC
Power Circuits
4. ANSI/SCTE 123 2006: Specification for “F” Connector, Male, Feed-Through
5. ANSI/SCTE 144 2007: Test Procedure for Measuring Transmission and Reflection
6. ANSI/SCTE 120 2006: Test Method for Balance Ratio