Measuring Cable Insertion Loss

The SARK-110 provides direct measurement of the insertion losses of a transmission line.

The insertion loss measurement setup for a typical transmission feed line is shown in Figure 1. Remove the antenna and connect a “short” at the end of the transmission line.

 

Figure 1, Insertion loss measurement setup

Procedure:

Step 1.

Power on the SARK-110 and select Scalar Chart mode: «Mode» «Scalar Chart»


Step 2.

Change the vertical left axis parameter to select CL (Cable Losses) parameter: «LeftY» «CL»


Step 3.

Optionally change the vertical right axis parameter to select Disabled: «RightY» «Disabled»


Step 4.

Set the center frequency «Freq» and span «Span»; or select a frequency preset «Preset». As an example select «Preset» «Full HF»


Step 5.

Connect the test port extension cable (MCX to BNC)


Step 6.

Perform OSL calibration at the end of the test port extension cable


Step 7.

Disconnect the antenna and connect an enclosed “short” load at the end of the transmission line


Step 8.

Connect the other end of the transmission line to the test port extension cable. A trace will be displayed on the screen if the SARK-110 is Run mode


Step 9.

Adjust the scale if necessary: «Setup» «Scale»


Step 10.

Set Marker 1 to track the minimum value of CL: «Marker1» «Tracking»«Min»«CL»


Step 11.

Set Marker 2 to track the maximum value of CL: «Marker2» «Tracking»«Max»«CL»


Step 12.

Calculate the insertion loss by averaging M1 and M2 values as follows:

 



Step 13.

Save the measurements and name the trace for historical documentation that can be used in the future to compare, check or verify changes in the transmission line performances: «File» «Save Data File»


In the example shown in the Figure 2, the analyzer was configured with the “Full HF” preset in order to sweep from 0.1 to 32 MHz. The measured loss minimum valley is at 842 kHz and has a value of 0.26 and the maximum peak is at 30.89 MHz and has a value of 2.89.

Therefore, the average insertion losses in this cable at this frequency range are:


Figure 2, typical insertion loss display in SARK-110 screen

The Field Mode is also very convenient for this type of measurement since it automatically provides the maximum and minimum values; see the Figure 3.


Figure 3, cable loss display in Field Mode

It is also possible measuring the cable insertion losses using the return loss parameter (RL). The procedure is the same as the described above but for calculating the insertion loss it is needed to apply the following formula:


The procedure in SARK Plots is similar. See in the Figure 4 a screenshot of the measurements of the same cable as shown in SARK Plots.

Figure 4, typical insertion loss display in SARK Plots