How can I check if the VNA works properly?

Execute the internal operator's check and the manual operators’ check.

Manual Operators Check for M980xA/P50xxA/E5080B
The operator's check in VNA firmware (Press System > Service > Operator's Check.) checks some primally signals internally. As a further check, this manual check procedure helps you to have more confidence that the VNA is working properly. This check does not guarantee the VNA meets the specification but the VNA mostly works normally if passed.

1. Port Char Correction Check / Measure a reflection (S11 to Sxx)
   i. No connection on the test ports
   ii. Preset
   iii. Click Math > Analysis > Statistic, then turn on the Statistic to display the Peak to Peak.
   iv. Confirm if the Peak to Peak is within +/- 1dB
   v. Click Sweep > Sweep Type > Log Sweep.
   vi. Set the start frequency at minimum limit (Up to 20 GHz models: 9 kHz, Above 20 GHz models: 100 kHz)
   vii. Confirm if the Peak to Peak is within +/- 1dB
   viii. Repeat this for S22 and until the maximum port. For example, until S44 for the 4 port model.

2. Power Level Check with Gain Low / Check the absolute value
   i. No connection on the test ports
   ii. Preset
   iii. Click Meas > Receivers > a1, Source port 1.
   iv. Click Power > Power Level, then set power level at +10 dBm
   v. Set the stop frequency at 30 GHz for above 20 GHz models.
   vi. Click Math > Analysis > Statistic, then turn on the Statistic to display the mean value.
   vii. Confirm if the mean is within (Power Level)+/- 2.5dB (Up to 20 GHz models), +/-3 dB (Above 20 GHz models)
   viii. Repeat the same steps for 0 dBm and -44 dBm.
   ix. Click Sweep > Sweep Type > Log Sweep.
   x. Set the start frequency at minimum limit (Up to 20 GHz models: 9 kHz, Above 20 GHz models: 100 kHz)
   xi. Set power level at 0 dBm.
   xii. Confirm if the mean is within (Power Level)+/- 2.5dB (Up to 20 GHz models), +/-3 dB (Above 20 GHz models)
   xiii. Repeat the same steps for -44 dBm.
   xiv. Repeat i) to xii) for port a2, 2 and until the maximum port a4, 4 for the 4 port model.

3. Power Level Check with Gain High
   i. Preset
   ii. Click Power > Power Level, then set power level at -44 dBm
   iii. Confirm the waveform
   iv. Change the power level at -45 dBm (Receiver Gain is changed to High)
   v. Confirm if the waveform becomes much smoother and less deviation.