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Stand Alone Frequency Accuracy Adjustment

This web page gives a stand-alone procedure for adjusting the time base in a FieldFox instrument.

This procedure performs the same function as the Frequency Accuracy Adjustment in N7841A TME software.

It may be used with any FieldFox model.

The program executes on a PC connected to the FieldFox via LAN. The FieldFox must be connected to a 10 MHz reference signal. The adjustment process sets the FieldFox internal time base to match the 10 MHz external reference.


  1. Install Keysight VEE 9 Runtime software on the PC if it is not already installed. See Install VEE Runtime below for instructions.
  2. Download file ff_freq_accy_adj.vxe from below to PC.
  3. Power up the FieldFox. The FieldFox internal temperature must be in an acceptable range for the adjustment to complete successfully. An error message will be generated if the FieldFox is not in an acceptable range. Warm up may require up to an hour. When the FieldFox is fully warmed up, its internal temperature may exceed the maximum acceptable temperature. If so, put the unit into standby to allow it to cool off. To view the internal temperatures on the FieldFox, press System, then Service Diagnostics, then Internal Temperatures. Hint: the FieldFox will warm up faster with the kick stand closed.
  4. Connect a 10 MHz reference signal at the top of the FieldFox.
  5. Establish a LAN connection between the FieldFox and the PC. See telnet setup for instructions. Note the IP address of the FieldFox.

Perform the adjustment

  1. Execute ff_freq_accy_adj.vxe on the PC. The file will be executed under VEE Runtime. A window will open for entry of the FieldFox IP address.
  2. Follow the prompts. The N9912A or N9923A selections will only adjust the TCXO. The N99xx selection will adjust both the TCXO and the VCXO.
  3. When the adjustment has completed successfully, a "Test Completed" message will be displayed. If the program is unable to complete successfully, an error message will be displayed.

Install VEE Runtime

  1. Go to  and search for "vee runtime"
  2. Download and install the most recent version available on your PC. A typical install is recommended.
  3. Execute the downloaded file. A typical install in recommended.
    • If you need to install Keysight IO Libraries, you will be prompted to install version 15 (or later) after installing VEE Runtime. A link to the Keysight IO Libraries Suite is available on the Downloads & Trials web page mentioned above.
    • If you need to install the .net framework, go to to download.

Notes on manually testing FieldFox frequency accuracy

  • Preset the FieldFox. Set the FieldFox for a long min sweep time (10 seconds or more) via the Sweep 3 key.
  • Connect a low pass filter to RF OUT on the FieldFox. A low pass filter is recommended because of the harmonic content of the FieldFox output. In the next step, measure the frequency of the FieldFox output at approximately the cutoff frequency of the low pass filter.
  • Set the FieldFox Frequency Span to zero and the Stop frequency to the desired CW output frequency for the measurement. (This may be done via the Freq/Dist key.)

Troubleshooting Notes:

If the program has trouble detecting the external 10 MHz reference, make sure the external reference can be detected manually before attempting the program again.

Release Date Version Version Description
2013-11-05 FFfeqAccyAdj 1.1 FFfeqAccyAdj 1.1

How to Download

  • Click the download button, select file and save.

How to Install

  • Please read the installation instruction guide from above.


  • Does Not Require a License

Installs on:


Operating System

  • Other Windows


  1. Stand Alone Frequency Accuracy Adjustment requires Agilent VEE 9 Runtime to work together. Go to search for "vee runtime".
  2. LAN connection between FieldFox and PC.

Supported Instruments

  • N9912A, N9923A, N9913A, N9914A, N9915A, N9916A, N9917A, N9918A, N9925A, N9926A, N9927A, N9928A, N9935A, N9936A, N9937A, N9938A