Focus recommends TRL Calibration Kits for applications such as load pull & noise parameters. Due to high reflection and low loss, tuner S-parameter measurements represent a challenge for VNA’s, because of error term determination and coupler directivity. Long experience has taught us not to rely on other calibration techniques than TRL (Thru-Reflect-Line). The popular SOLT technique is conditionally useable, but not guaranteed, up to 4GHz. The much convenient ECal method has provided questionable and inconsistent results. Our Customers are advised to be very careful with VNA calibrations, because the whole measured data depends on that.