Spirent DLS 6700, Operating Manual

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DLS 6700 Operating Manual
Page A-2 7104000557 Spirent Communications
A.2 Common Errors
There are three common errors:
• Coupling between input and output via the two transformers. When trying to
measure attenuations of 60 dB or so, approximately 1/1000 of the input voltage,
or 1/1000000 of the input power is present on the output. It is very easy for
transformers - or even wires - placed close to each other to couple together far
more than this. Take care to keep inputs and outputs separate.
• The use of a high impedance measuring device with no load from tip to ring at the
receive end. This results in reflections due to a bad mismatch at the end of the
line, and leads to very peculiar response curves.
• Ground injected directly onto the tip or ring of the wireline simulator. This almost
always leads to a very noisy spectrum, with high background noise levels and
often harmonically related spectrum “spikes”.
A.3 Typical Attenuation Characteristics
Figure A3.1 DLS 6700 - Attenuation at 2 kft, 4 kft and 6 kft
Attenuation Characteristics
-80
-60
-40
-20
0
0.0 1.0 2.0 3.0 4.0 5.0
Frequency (MHz)
A
tten
u
a
ti
o
n
2 kft
4 kft
6 kft
Theory
Measured