Technical data

46 Chapter 2
One Port Insertion Loss
Measuring One Port Insertion Loss
One Port Insertion Loss
Measuring One Port Insertion Loss
The one port insertion loss measurement allows you to quantify signal loss in a
cable or other device without connecting both ends of the cable or device to the test
set. This measurement can be especially useful in measuring the loss of a feedline
connected to the antenna on a tower. This method of measuring antenna feedline
insertion loss is accurate for results up to 10 dB.
This measurement is less accurate than Two Port Insertion Loss. When it is not
practical to connect both ends of a device to the test set or for insertion loss
measurements greater than 10 dB — for example when measuring a 40 dB high
power attenuator — it is better to use Two Port Insertion Loss.
NOTE The test signal emitted from the SWR port is a sine wave, swept from the starting
frequency to the stop frequency. When testing cables that are attached to antennas,
test signals are radiated, and these test signals can cause interference. Verify that the
signal used for the test cannot cause interference to another antenna.
Calibration - Minimizing your Workload
The One-Port Insertion Loss calibration is the same calibration as performed for
the
Return Loss and Distance to Fault (when it is performed with Frequency
Range set to manual) measurements. If you have already calibrated for any of these
three measurements, the calibration will apply to the other two measurements and
“Calibrated” (together with the frequency range over which the calibration was
performed) will be displayed on top left of the screen for all three.
The
Distance to Fault calibration (when it is performed with Frequency Range set
to Auto) is only valid for other Distance to Fault measurements that are also
performed with Frequency Range set to Auto, and then only if the calibrated
frequency range falls within the previously calibrated frequency range.
If you have not previously performed a calibration, the word “Uncalibrated” appears
at the top left of the measurement screen.
It is important that you keep the calibration frequency range as close as possible to
the actual sweep frequencies you intend using for the measurement or
measurements. Calibrating over a large frequency range (for example, 1 GHz) when
you only intend measuring over a much smaller range (a few kHz, for example) will
induce inaccuracies into your results.
If you plan to perform a combination of
One-Port Insertion Loss measurement,