Various 2-port calibrations are available in VNA Mode. Transmission response is the simplest and requires only one connection during calibration, but it does not correct for test port match errors. 1-Path 2-Port calibration requires four calibration connections and corrects for the transmit port match, but does not correct for the receive port. Full 2-port calibration requires seven calibration connections and corrects for both test port match errors. The full 2-port calibration technique offers the most accuracy.

For accurate results, the MS2085A/89A must be calibrated at the ambient temperature after allowing for warm-up time (10 minutes) and before making any measurements. The instrument must be recalibrated whenever the setup frequency changes, whenever the ambient temperature changes by an amount that has more than likely rendered the calibration invalid, or whenever a test port extension cable is added, removed, or replaced. For an example of measurement improvement after calibration, refer to Only one calibration is available at one time. Performing a new calibration overwrites any existing calibration. You can, however, store a measurement setup, which also stores the calibration. You can therefore have multiple calibrations available (as long as the calibration settings and conditions continue to apply). Refer to VNA Calibration and Measurements to deep dive into CALIBRATE menu that includes calibration methods and setup options..

Calibration data are saved when you save a Setup file. When you recall a setup, the calibration remains valid if instrument conditions (such as temperature) remain within the calibration tolerance.

When you perform a calibration, the correction coefficients are calculated for specific S‑parameters (depending on the type of calibration chosen) and for instrument settings (frequency range, number of points, and power level). The term “calibration correction” refers to the measurement correction coefficients that are applied to measurements as a result of your calibration.

When calibration is completed it applies to all S‑parameters. For example, if a Full S11 (1‑port) calibration is performed, then only traces that measure S11 have a valid calibration. For those traces, the calibration status is displayed as S11 Cal: On in the trace card of the status panel. All other traces that do not measure S11 will displayed as S11 Cal: Off to indicate that no valid calibration is available for those traces. The calibration status is off by default. The calibration correction can also be turned off manually by toggling off the USER CAL under the CALIBRATE menu. In that case, the calibration status is shown as CAL: OFF for all traces that have valid correction data available.

When you have INTERPOLATE set to off, you cannot modify the frequency range or the source power level, or increase the number of points. You can, however, decrease the number of points without forcing the calibration to become invalid.

If you reduce only the number of points, then the frequency range is not changed. The MS2085A/89A finds a subset of the original points in the sweep that can be used. You can therefore notice that the instrument may not use the exact number of points that you have entered. It picks a specific number of points that allow the calibration correction to continue to be valid. Data points can be set using DATA POINTS under SWEEP menu.

If INTERPOLATE is set to on, then you can reduce the frequency range and modify the number of points without invalidating the calibration. In that case, the calibration coefficients are regenerated (interpolated) to match the new settings.

Only one calibration is available at one time. Performing a new calibration overwrites any existing calibration. You can, however, store a measurement setup, which also stores the calibration. You can therefore have multiple calibrations available (as long as the calibration settings and conditions continue to apply). Refer to VNA Calibration and Measurements to deep dive into CALIBRATE menu that includes calibration methods and setup options.