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Questions and answers about VNA calibration kits

This page is a addition to the FAQ, for short technical questions about vector network analyzers, and the calibration kits, which do not merit a webpage on their own.

  1. Why is my 6 GHz 8753 set to a maximum frequency of 3 GHz?
  2. Why do I get the message Additional Standards Required during calibration?

Question: Why is my 6 GHz 8753 set to a maximum frequency of 3 GHz?

When you purchase an 85033 SMA calibration kit, or an 85054 N calibration kit it can be purchased with a floppy disk for an 8753. If you then load the coefficients from the disk, the frequency span of the VNA will be set from 300 kHz to 3 GHz, even if you have a 6 GHz VNA that covers 30 kHz to 6 GHz. This might alarm some people, but there is nothing to worry about. The reasons are explained below.

Answer, to why the maximum frequency is set to 3 GHz on a 6 GHz 8753.

When Kirkby Microwave create a floppy disk for a VNA such as the 8753, 8510, 8719, 8720 or 8722, the calibration kit file specifies the upper frequency limit of the kit. This is to prevent you calibrating with the kit outside the range where it is useful. So the upper frequency limit will be set from 6 to 18 GHz depending on the kit purchased.

When disks are created for an 8753, we actually create them on a 3 GHz 8753ES. The coefficients are sent over the GPIB to the 8753, then the 8753 writes the coefficients to the floppy disk. Since a VNA covering 300 kHz to 3 GHz VNA is used to write the files, that is saved, so the state of the machine can be recalled later. The kit will still work to its upper frequency limit, as the coefficients would have been measured on a 20 GHz VNA, not a 3 GHz 8753. But since a 3 GHz 8753 is used to write the coefficients, we can't put the span any greater than 3 GHz. (There are ways we could circumvent this, but there seems little point us doing so, as it does not warrant the extra work, when the kit will work perfectly fine with a 6 GHz 8753.)

Question: Why do I get the message "Additional Standards Required" during calibration?

Sometimes, when calibrating a VNA, you will get a message like "Additional Standards Required". The calibration will never complete, and this can be frustrating. The reasons are explained below.

Answer to why the message "Additional Standards Required" may be seen.

If you try to use a calibration kit outside the specification for the frequency range, then the VNA will not calibrate. For example, if you you purchase our SMA calibration kit, then try to calibrate with a maximum frequency of 15 GHz, the VNA expects you to use other calibration standards that covers the frequency range of our SMA calibration kit, which is 7-12 GHz, depending on what option is purchased. Since you don't have the standards suitable for use to 15 GHz in our SMA kit, the calibration will never complete, but will give the error "Additional Standards Required"

Likewise, if you try to calibrate with a WR90 waveguide calibration kit, such as our X-WR90-3f, over the frequency range 8 to 12 GHz, this will also fail, as the kit is specified over the range for which WR80 is used (8.2 to 12.4 GHz).

Note, our policy of limiting the frequency range to that of the kit is different from HP, Agilent and Keysight, who normally set the maximum frequency as 999 GHz, with two exceptions:

  1. When kits have sliding loads, the frequency range of the lowband load is set properly, In the case of our Agilent 85054B calibration kit, the lowband load is specified as 0 to 2.001 GHz, and the sliding load as 1.999 GHz to 999 GHz. Again, given this is an N kit, and the maximum frequency of the N connector is 18 GHz, we feel it unwise to specify the maximum frequency of the sliding load as 999 GHz, but at least these definitions prevent the sliding load being at low frequency, where it would be totally useless.
  2. In the case of waveguide calibration kits, HP, Agilent and Keysight set the frequency range exact as Kirkby Microwave would - for example, for Keysight X11644A WR90 8.2 to 12.4 GHz waveguide calibration kit, the frequency range of the calibration kit definitions is set from 8.2 to 12.4 GHz, so you can not calibrate outside that frequency range.

Kirkby Microwave Ltd is registered in England and Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT.