External Source Configuration

Once configured, an external source appears in VNA dialogs as though it were an internal source. This capability requires FOM Option 080.

In this topic:


How to Configure an External Source

  1. Important: Create an External Source device by name (one-time). Learn how.(Separate topic)

  2. Then click Device Properties to Configure the External Source. (This topic)

VNA Applications have additional methods of launching this dialog.

Using front-panel
[softkey] buttons

Using Menus

  1. Press system

  2. then [Configure]

  3. then [External Device Configuration]

  1. Click Utility

  2. then System

  3. then Configure

  4. then External Device Configuration

See Remotely Specifying a Source Port


External Source Configuration dialog box help

This dialog box is used to make external source settings.


Important Notes about External Sources

  • First create an External Source (device) by name (one-time). Learn how.(Separate topic)

  • Once you create and activate an external source from the Configure an External Device dialog, it becomes available from the following VNA dialog boxes as well as the softkeys and entry toolbar, as if it were an internal VNA source.
    Use the following dialogs to set the state, frequency, and power level of the external RF source

  • By default, an external source is de-activated when the VNA is Preset or when a Instrument State is recalled. This behavior can be changed with a Preference setting.

  • External Keysight sources are usually limited to 1601 points with List-sweep mode. To 'work around' this limitation, divide the measurement among multiple channels. For example, to attain a sweep of 3200 points, create two channels of 1600 points. You can also use manual source control which supports Step-sweep mode. In this mode an external source can have up to 65,535 points.  See Synchronize an External Source for help with manual source control.

  • External sources should always share the same 10 MHz Reference signal as the VNA. Connect a BNC cable from the VNA 10 MHz Ref Output to the External Source Input.

  • All newly-activated sources are preset, with source power OFF. Source power must be turned ON in the Power dialog.  Frequency Offset must be enabled in the FOM dialog.

  • The same source can NOT be used more than once in the same channel.

  • The VNA automatically controls all trigger settings for the external source.

  • See EXG Sources configuration note.

Source Settings

Timeout (sec)  Sets the VISA timeout and will stop processing additional SCPI commands on the first error and will put the measurement into hold.

Dwell per point (ms)  Applies a dwell in Hardware List triggering ONLY. Set the time (in milliseconds) the external source will wait before data acquisition.

Enable Modulation Control - Enables modulation of an external modulation source to be controlled from a source dialog.

Edit Commands  Provides a method to send SCPI commands to AGGeneric (not listed) sources.

Trigger Settings and Physical Connection diagrams

Note: The VNA controls ALL external source trigger settings automatically (except for those on this dialog). All settings in the External Trigger dialog are ignored.

Trigger Mode

Software CW (GPIB)  Slowest method.

  • The external source receives each CW frequency from the VNA over GPIB, USB, or LAN. No other trigger cables are required. Although a Trigger Port selection may be available, it is NOT used.

Hardware List (BNC)  Fastest method (not available in M937xA).

  • NOT available for AGGeneric (not listed) sources.

  • The external source receives a list of CW frequencies from the VNA, then receives trigger signals though a rear-panel connector when appropriate from the VNA.

  • If the number of data points used in the measurement exceeds the capability of the external source, the VNA automatically switches to Software CW (GPIB) trigger mode. This will slow the measurement significantly.

Trigger Port  Used ONLY for Hardware List Trigger Mode. Select the VNA rear panel connector to be used for triggering. The sources must be connected as follows:

  • For ONE or TWO external sources, connect each source to an AUX trigger pair. See rear panel Aux connectors.

    • Source Trig Out connects to VNA Aux Trig In (1 or 2)

    • Source Trig In connects to VNA Aux Trig Out (1 or 2)

The following diagram shows the connections between the PNA (AUX TRIG 1 or 2 can be used) and N519xA UXG signal generator.

  • For more than TWO sources, some will need to be connected using the following daisy chain image. For example, with three external sources, two could be daisy-chained to Aux 1 while the third is connected by itself to Aux 2.



  • Source 1, which receives the trigger out of the PNA, must be the first source listed on the External Devices Configuration dialog box. Devices are listed in the order in which they are created. You may have to delete, then re-create a source to move it down on the list.

  • Connect EXG sources as follows:

    • EXG rear-panel label TRIG 1 connects to VNA AUX TRIG 1 OUT

    • EXG rear-panel label TRIG 2 connects to VNA AUX TRIG 1 IN

Note: The VNA AUX TRIG 2 can be used instead of VNA AUX TRIG 1.



Generic Source Commands dialog box help

Enter the SCPI commands that control the following functions on your AGGeneric (not listed) source. A field without a SCPI command entered will be ignored and that function will not be set.

To launch this dialog, click Edit Commands on the External Source Properties dialog.

Operation Complete (*OPC) .

Preset   Presets the source

Set CW Frequency  Sets CW Frequency

Set CW Sweep Mode  Sets source sweep mode

Set Power  Sets source power

Set Power State  Turns power ON or OFF