Calibration Status Codes

The calibration status indicator appears at the bottom of the NanoVNA-F V3 main screen (region 4). It uses a compact string of letters and symbols to communicate the current calibration state at a glance.

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Status Code Reference

Code	Meaning	Description
O	OPEN done	The open calibration standard has been measured
S	SHORT done	The short calibration standard has been measured
L	LOAD done	The 50-ohm load calibration standard has been measured
T	THRU done	The through calibration between PORT1 and PORT2 has been measured
C	Calibrated	Calibration coefficients have been computed (you tapped DONE)
*	Not saved	Calibration data exists in memory but has not been saved to a storage slot — it will be lost on power-off
c	Interpolated	The current sweep range differs from the calibrated range, so the device is using interpolated calibration data
Cn	Slot number	Calibration data is loaded from storage slot n (where n is 0 through 12)

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Reading the Status String

The codes appear together as a combined string. Here are common examples and how to interpret them:

During Calibration

Display	Meaning
O	Only the open standard has been measured so far
OS	Open and short standards measured
OSL	Open, short, and load measured — ready for THRU if S21 calibration is needed
OSLT	All four standards measured — tap DONE to compute coefficients

After Calibration

Display	Meaning
OSLT C*	Calibration is complete but not saved. Power-off will discard it.
C0	Device is using calibration data from slot 0
C5	Device is using calibration data from slot 5
c0	Calibration from slot 0 is being interpolated to the current frequency range
c3	Calibration from slot 3 is being interpolated

Caution

The * (asterisk) means your calibration is volatile. Always save to a slot after calibration: CAL > CALIBRATE > DONE > SAVE n

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When Interpolation Occurs

The lowercase c appears when the current sweep start/stop frequencies or point count differ from the settings that were active when the calibration was performed. The device interpolates the stored calibration data to estimate correction values at the new frequencies.

Interpolated calibration is less accurate than a native calibration at the exact sweep settings. For best results:

1. Set your desired frequency range before calibrating
2. Avoid changing the sweep range after calibration
3. If you must change the range, recalibrate at the new settings

Tip

You can store up to 13 calibrations (slots 0-12), each at a different frequency range. Use the RECALL function to switch between them without recalibrating.

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No Calibration Status

If no calibration status string is visible at the bottom of the screen, it means:

• No calibration data is loaded, or
• Calibration has been explicitly disabled via CAL > APPLY (toggled off)

In either case, measurements are uncorrected and should be treated as approximate.

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Checking Calibration via Console

You can also query the calibration status from a serial terminal:

cal

This returns the same status string shown on the display, along with additional calibration details.