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I lost my Keysight E5500 Phase Noise System license key. How do I obtain a permanent replacement license key?

Keysight (and legacy Agilent/Hewlett-Packard) phase noise systems typically consist of a license key enabled personal computer (PC) and a phase detector (at minimum). The phase detector test set model numbers are either 70420A or N5500A. In order to obtain a permanent replacement phase noise system license key, the phase detector test set (70420A or N5500A) serial number is required:

  • To view the serial number on the 70420A phase detector test set, drop down the hinged bezel.
  • For the N5500A phase detector test se,t the serial number tag is located on the front panel.

Additionally, for both the 70420A and the N5500A phase detector test sets it is recommended the printed phase detector test set serial number is confirmed via GPIB execution of a *IDN? identification query. The *IDN? query is executed via the Phase Noise PC controller and the Keysight I/O libraries.

If the GPIB based *IDN? query reports serial number 0000A00000 this is a special configuration. The configuration defines a model 70420A special option H02. These phase detector test sets all share one permanent license key which will work for all 70420A opt H02 configured phase detector test sets. The permanent license key for all 70420A opt H02 phase detector test sets identified via GPIB as serial number 0000A0000 is:


For all other serial numbers, please obtain the serial number reported over the bus, confirm this matches the printed serial number and note if any of the following items are germane to the Phase Noise system in question:

E5480A LTU ACM for E1430A
E5490A LTU ACM for programmable delay line
E5491A LTU ACM for E1437A
E5492A LTU ACM for E1420B counters
E5495A LTU remote SCPI client SW
E5496A LTU ACM software for 2030, 2040, 2050 Series IFR Marconi sources

Please send an email to and in the subject line include the text “Request for permanent Phase Noise license key”. Also, provide the following required information.

  1. Model and serial number of 70420A or N5500A phase noise test set as reported over the bus.
  2. Any required LTU ACM from the list above.
  3. Phase noise software version as determined via the Phase Noise Application Software - Help – About selection.
  4. Windows operating system:
    • Windows 7 32-bit and Windows XP are currently supported.
    • Windows 7 64-bit is not currently supported. 
    • Windows 2K and Windows NT are no longer supported.
  5. Your contact information to include:
    • First and Last name 
    • Email address 
    • Phone numbers for desk – lab – cell phone number, as applicable
    • Company name
    • Company address

For more information about phase noise, please visit Phase Noise Measurement.