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Patch-cord
Bend Radius Testing Analysis
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This white paper contribution is part of a two part
contribution on bend- radius analysis for patch cords that was submitted
and presented at the March 2nd 2000, EIA/TIA, TR 42.1 committee
meeting in Orlando, Florida. The contributions for testing and field
analysis of bend radius provided the support for the TR 42.1 committee
to provide a two-third vote to adopt a one times (1x) the cable
diameter for UTP patch cords, bend radius in the future 568-B.1
standard. This new standard is to be ratified by the end of this
year.
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Patch-Cord
Testing Series
Patch-Cord Sampling
- A total of 12 different manufacturers of patch cord assemblies
were selected.
- A sample of 3 cords, 10 foot each (Category 5e) from each of the
12 manufacturers was provided (for a total of 36 cords).
- Ten of the manufacturers (30 cords) were purchased through distributors.
- Two of the manufacturers (6 cords) were donated directly from
the manufacturer.
- Of the original 36 patch cords, one cord failed due to open pairs
on the patch cord assembly's plug. This provided for a total 35
cords to test and analyze.
- Of the 35 cords tested to Category 5e patch cord, Return Loss
specifications, 8 failed the controlled test (no bend).
- The 8 failed and the 1open pair assembly cord accounted for a
25% failure rate of patch cords coming out of the factories.
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Two
Bend Patch-cord Testing Series |
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Patch
Cord Testing Procedure
Using the DCM PCT-350 System, which includes an
automatic balanced switching device with a high-frequency interface
combined with a HP 8753-E network analyzer and computer, Return
Loss was measured to the Category 5e (568-A-5 standard) for patch
cords.
A jig was used with two, 2-inch mandrels (1-inch
radius - 4 times the cable diameter) based on 0.25-inch maximum
size diameter for UTP-four pair patch cables. 0.5-inch mandrels
(.25 inch radius) were used to measure one times the cable diameter.
All the bending was performed in a set of two (180-degree bends)
on each patch cord under test.
The following measurements were taken and recorded
in plots 1 through 4 after the cords were secured in place. All
35 patch cords were tested individually in each of the four measurement
states (below) for a total of 140 tests.
- Control measurement - no bends (measurement #1, plot 1)
- Two, two inch mandrels (measurement #2, plot 2)
- Two, 0.5 inch mandrels (measurement #3, plot 3)
- Two, collapsed points (measurement #4, plot 4)
After all cords were tested under the four different
measurement states, they were combined into comparison analysis
-- plot #5.
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Lowest
Margin from CAT5E Patch-cord Limit Line (MHz) |
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Average
Worst Case Margin.from CAT5e Patch Cord Limit Line |
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Patch-Cord
Testing Series Conclusion
As indicated in the summary analysis (plot #5) the
fully collapsed cords measured a 1.14 dB loss (average) when compared
against the control cords (average). This indicates that this measurement
state (fully collapsed) must be taken into consideration during
patch- cord testing procedures.
Supporting
Contribution
TIA TR-42.7.2 - Patch Cord Minimum Bend Radius,
#028 by CommScope
Recommendations
for Patch Cords Testing
To protect the consumers from field installations
practices provide that fully collapsed cord test be inserted into
the Mechanical Handling Stress Test as defined in the 568-A-5 standard
(printed below).
G.8 Mechanical handling stress test Modular patch
cords shall comply with the return loss requirements of 6.3.1 after
each step listed below. For all test conditions, a maximum 150 mm
(6.0 in) of undisturbed cable shall be allowed to enter the test
fixture at both ends.
1. Test the patch cord uncoiled.
2. Loop the cord (following the natural cable lay) into a 150 mm
(6 in) diameter loop, up to ten loops total, and test.
3. Compress the coil into an ellipse and fully collapse at the bending
points in the ellipse and test.
4. Rotate one end of the coiled ellipse by 180 degrees (following
the natural cable lay) to form a figure eight in the non-conductive
trough and test.
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Four
Bend Channel Testing Series |
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Channel
Testing Series
Utilizing the same testing equipment as used in
the previous Patch Cord Testing Series and selecting previously
profiled cords, two cords (10 ft.) were inserted into a 90-meter
basic link to establish a channel. Although the patch cords were
inserted into a channel, we also provided basic link measurement
limits when testing for comparison. The basic link limits are more
stringent (after 20 MHz) for RL than channel.
A total of five different channels were constructed
from the same 90-meter link utilizing ten different cords that were
pre-qualified (profiled). A jig was used to provide controlled bending
(180-degrees) two cords installed in the constructed channel. A
total of four bends was applied (two on each cord) and measurements
taken to Category 5e channel and basic link requirements.
The following measurements were taken and recorded
in plots 1A through 4A after the cords were secured in place for
each of the five channels.
- Control measurement - no bends (measurement #1A,
plot 1A)
- Four, two inch mandrels (measurement #2A, plot 2A)
- Four, 0.5 inch mandrels (measurement #3A, plot 3A)
- Four, collapsed points (measurement #4A, plot 4A)
After all five channels were tested under the four
different measurement states they were combined into comparison
analysis -- plot 5A.
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Lowest
Margin From CAT5E Channel Limit Line (MHz) |
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Channel
Testing Series Conclusions
The channel limit is the most important factor when
testing components of a system. Due to the fact that the sum of
all individual components in a channel do not add up to the performance
of that channel, it is imperative that the channel be tested with
the cords used for that channel. This will reflex the interaction
and provide the true performance of that channel.
The effects of return loss on the degree of bending
patch cords in a channel has no direct correlation to performance.
As indicated in the testing of four, one-inch radii (2-inch mandrels)
inserted in a channel was the worst in performance of the different
degrees of bends applied and still had a 1.18 dB margin over the
more stringent Category 5e basic link limits when tested in a channel.
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Average
Worst Case Margin.from CAT5e Basic Link Limit Line |
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Patch
Cord Channel Recommendation
Provide a minimum bend radius, under no load conditions
of one times (1x) the cable diameter for 4-pair UTP patch cords.
TR
42.1 Committee Response
The committee ratified the above recommendation
by two third votes in the favor of a one-time the cable bend radius
(1x) for UTP patch cords.
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See
White paper - TIA/EIA TR-42.7contribution #448 for Patch-cord Field Analysis |
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PerfectPatch
Copyright
2009 by PerfectPatch, Inc. All rights reserved. |
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