> Calibration
> For accurate results, the instrument must be calibrated before making any measurements.
> The Cable and Antenna Analyzer mode requires calibration standards for OPEN, SHORT, and LOAD (OSL), which are sold separately. Alternatively, you can use the internal InstaCal. The external InstaCal Calibration Module is NOT compatible with the Site Master S331L. For Transmission measurements, the external USB sensor itself is used as part of the calibration step, and no additional components are needed.
> The instrument must be re-calibrated whenever the temperature exceeds the calibration temperature range window or when the test port extension cable is removed or replaced. Unless the calibration type is Flex, the instrument must also be re-calibrated every time the setup frequency changes. Refer to Calibration for details on how to perform a calibration.

> Note | Anritsu recommends allowing the S331L to warm up for 5 minutes to typical operation temperature before calibrating. The instrument will require a new OSL calibration if the internal instrument temperature changes more than 20 ºC after calibration.