BIRD BirdTechnologies SignalHawk SH-36S Operating Instructions Manual page 50

Note: If the unit is operating without valid calibration, the text in the
cal area of the status bar will be red and say "Off". If it has a calibration,
the calibration method will be listed in black text.
Note: For most isolation and gain measurements, only a thru cal
(Cable from RF Out-In) is needed.
Figure 16 Example, Calibrate Menu
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