Return Loss Measurements; 1-Port Cable Loss Measurements; Return Loss Measurement; 1-Port Cable Loss Measurement - Keysight N9923A FieldFox User Manual

Return Loss Measurements

Return loss can be thought of as the absolute value of the reflected power as
compared to the incident power.
When measuring an OPEN or SHORT, all incident power is reflected and
approximately 0 dB return loss is displayed.
When measuring a LOAD, very little power is reflected and values of 40 dB to 60 dB
are displayed.
The minus sign is usually ignored when conveying return loss. For example, a
component is said to have 18 dB return loss, rather than –18 dB.
How to measure Return Loss
 Connect the cable or any adapter used to connect the device under test (DUT).
 Select Preset then
 Select Mode then
 Then
 Press Freq/Dist and enter
 Press Meas Setup 4 then
 Disconnect the cable or DUT and press Cal 5 then follow the calibration
 Reconnect the cable or DUT.
 The return loss trace is displayed on the FieldFox screen.

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.
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 49) and Averaging. (page 47).
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
CAT (Cable and Antenna Test) Mode - Option 305
Preset
CAT
(Default measurement).
Return Loss
calibrating.
prompts.
then
More Cable Loss (1-Port)
measurement.
Returns the FieldFox to known settings.
(Cable and Antenna Test)
and frequency values of the measurement.
Start Stop
to make appropriate settings before
Settings
.
and frequency values of the
Start Stop
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