Figure 5-36 TELECOMS MODE: Simple Termination. Wayne Kerr 3260B

Advanced Operation 5–33

Figure 5-36 TELECOMS

MODE: Simple Termination

Figure 5-37 TELECOMS

MODE: Direct Damped

Termination

Figure 5-38 TELECOMS

MODE: Damped Termination with DC Blocking Capacitor

Two sets of measurement leads are required; see Figure 5-2 for the connection protocol. To meet the specified accuracy, 4-terminal connection must be used. The general procedure when using TELECOMS MODE is as follows.

1) Select the Menu control key, followed by the TELECOM soft key.

2) Connect the measurement leads, see Figure 5-2.

3) Select 4-terminal measurement.

4) From TELECOMS MODE select the CALIBRATE soft key.

5) Refer to section 4.3 and perform the following trims. a) O/C Trim (Pri) b) S/C Trim (Pri) c) O/C Trim (Pri–Sec) d) S/C Trim (Sec)

6) Select the TELECOM soft key to return to TELECOMS MODE.

7) Select the terminating options required..

8) Change the setup parameters as required, i.e. drive level, frequency and terminating component values, being careful not to exceed the limitations of the transformer.

9) Connect Primary and Secondary leads to the appropriate transformer windings.

10) Press the Start soft key to initiate the test. The measured values of insertion loss (I.L.) and return loss (R.L.) will be displayed on the screen.

5.13.1 Example

This example will take the user through the process of measuring the insertion loss and return loss of a line matching transformer. The settings used are examples only and the user may substitute other settings, subject to the limitations of the component to be measured. The analyzer should be powered up with the test leads or fixture connected to the front panel BNC connectors according to the connection protocol for transformer/telecom mode (see Figure 5-2).

1) Press the front panel Menu control key. The MAIN MENU will be displayed.

2) Press the TELECOM soft key. TELECOMS MODE will be displayed.

5–34

Advanced Operation

3) Press the CALIBRATE soft key and perform the trims listed in section 5.13 paragraph 5).

When the trims are complete, press the TELECOM soft key to return to TELECOMS

MODE.

4) Using the Simple/Damped soft key, select Damped termination.

5) Using the Direct/Blocked soft key, select Blocked termination.

6) Using the navigation keys, highlight and set each of the following parameters in turn. Use the and navigation keys to highlight a parameter and the data entry keypad or and

navigation keys to alter the highlighted parameter setting. Settings may be altered one step at a time, or continuously by holding the navigation key down.

4.0000kHz

Z

0

: 600.0 Ω (default

Cb : 1.000MF (default value)

7) Connect the transformer to the test leads or fixture.

8) Press the Start soft key. The measured values of insertion loss (I.L.) and return loss (R.L.) will be displayed on the screen.

Figure 5-39 Example of Measuring Insertion Loss and Return Loss in TELECOMS MODE

5.13.2 TELECOMS MODE Parameters

The following TELECOMS MODE parameters are selectable with the soft keys to the right of the display.

Start

When the test conditions have been set and the transformer connected to the test leads or fixture, pressing the Start soft key

Advanced Operation 5–35

Simple/Damped

Direct/Blocked

CALIBRATE

performs a test of Insertion Loss (I.L.) and Return Loss (R.L.).

Toggles between Simple termination, shown in Figure 5-36, and a

Damped termination network, shown in Figure 5-37. See also

Direct/Blocked below.

This soft key becomes available when Damped termination is selected (see Simple/Damped above). Direct termination is shown in Figure 5-37. Blocked termination is shown in Figure

5-38 and features a DC blocking capacitor in the transformer signal source.

See section 4.3.

The following TELECOMS MODE parameters are those displayed in the bottom left-handcorner of the screen, shown in Figure 5-39.

Drive Level

Set by highlighting the parameter with the and navigation keys, then altering the setting in pre-determined steps with the and navigation keys, or by using the data entry keypad. The range is:

–28.0dBm to 16.0dBm.

Measurement Frequency Set by highlighting the parameter with the and navigation keys, then altering the setting in pre-determined steps with the and navigation keys, or by finer increments using the data entry keypad. The range is:

100Hz to 20kHz

Z

0

Rt

Ct

Fine or coarse frequency steps are available. Coarse steps vary in increments of between 20% and 33%; fine steps vary in increments of 1% or less. Set fine or coarse steps from the

SETTINGS page—see section 5.18, or use code 10 (fine steps) or code 11 (coarse steps)—see section 4.2.6.1

The signal source impedance. The range is:

50.00Ω to 2.000kΩ default = 600.0Ω

The network terminating resistor. The range is:

50.00Ω to 2.000kΩ default = 600.0Ω

The network terminating capacitor. Only available when Damped termination is selected. The range is:

0.000F to 9.999TF default = 4.700nF