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Reconnect the cable or DUT.
The return loss trace is displayed on the FieldFox screen.
NOTE
If the DUT just measured is a cable, and if you are now going to perform a 1-port
cable loss measurement, save the return loss measurement data to memory.
Doing this allows you to omit steps 10 and 11 on page 27 in the procedure for
making a 1-port cable loss measurement.
1-Port Cable Loss Measurements
While all cables have inherent loss, weather and time will deteriorate cables and
cause even more energy to be absorbed by the cable. This makes less power
available to be transmitted.
A deteriorated cable is not usually apparent in a Distance to Fault measurement,
where more obvious and dramatic problems are identified. A Cable Loss
measurement is necessary to measure the accumulated losses throughout the
length of the cable.
A 2-port Insertion Loss measurement is usually more accurate than a 1-port
Cable Loss measurement. However, to perform a 2-port Insertion Loss
measurement, both ends of the cable must be connected to the FieldFox, and the
FieldFox must have option 110 installed.
NOTE
In high-loss conditions, a Cable Loss measurement becomes „noisy‟ as the test
signal becomes indistinguishable in the FieldFox noise floor. This can occur
when measuring a very long cable and using relatively high measurement
frequencies. To help with this condition, use High Power (page 24), and
Averaging. (page 22).
How to make a 1-port Cable Loss Measurement
1. Press Preset then Preset.
2. Then
3. Connect the cable to be tested.
4. Press Freq/Dist and enter
5. Press Sweep 3 then
6. Remove the cable to be tested.
7. Press Cal 5 , then
8. Follow the prompts to perform calibration at the end of the jumper cable or
9. Connect the cable to be tested.
NOTE
Low-level standing waves (also also known as „ripple‟) which may be visible in
reflection measurements, can hide the actual loss of the cable. Steps 10 through
13 can minimize the ripple. Perform the measurement with and without steps 10
through 13 and choose the method with the least amount of ripple.
10. Connect a LOAD at the end of the cable to be tested. This limits the
11. Press Trace 6 then
26
then
More
Cable Loss (1-Port)
measurement.
Min Swp
trace is visible on the screen. The amount of time that is required increases
with longer cable lengths. Learn more in the Supplemental Online Help:
http://na.tm.agilent.com/fieldfox/help/
QuickCal
adapter. Learn more about Calibration on page 51.
reflections to faults that are located in the cable under test.
Data->Mem
.
and
frequency values of the
Start
Stop
Time. Increase the Sweep Time until a stable
or OSL.
to store the trace into Memory.
N9912A FieldFox User's Guide
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