Scale and Reference

Proper scaling ensures your measurements are displayed at the optimal zoom level. The NanoVNA-H provides auto-scaling and manual control over scale per division and reference position.

Auto Scale

The quickest way to adjust scaling is using auto scale:

1. Tap the screen to open the menu
2. Navigate to DISPLAY > SCALE
3. Tap AUTO SCALE to automatically fit the current trace to the display

Note

Auto scale adjusts both the scale per division and reference position to show the full range of current data.

Manual Scale Adjustment

Set Scale Per Division

1. Go to DISPLAY > SCALE > SCALE/DIV
2. Enter the desired value using the keypad
3. Tap the appropriate unit or ENTER to confirm

Common scale values by format:

Format	Typical Scale	Notes
LogMag	10 dB/div	Standard for return loss
LogMag	1 dB/div	Fine detail for filter passband
Phase	45 deg/div	Shows full 360 degree range
SWR	1/div	For low SWR antennas
Smith	1/div	Normalized to Z0
Delay	varies	Depends on DUT

Set Reference Position

The reference position determines where the reference value appears on screen:

1. Go to DISPLAY > SCALE > REFERENCE POSITION
2. Enter a position value (0-8, where 0 is bottom, 8 is top)
3. Tap ENTER to confirm

Position	Location	Common Use
0	Bottom line	Positive values above
4	Center	Phase measurements
7 or 8	Top area	Return loss (negative dB)

Set Reference Value

1. Go to DISPLAY > SCALE > REFERENCE VALUE
2. Enter the reference value at the reference position
3. Tap the appropriate unit to confirm

Tip

For return loss measurements, set reference position to 7 or 8 and reference value to 0 dB. This puts 0 dB at the top with attenuation shown below.

Electrical Delay

Electrical delay compensates for the phase shift introduced by cables and connectors between the calibration plane and the DUT. The firmware stores separate delay values for S11 and S21 channels, and applies the correction by rotating the complex measurement data at each frequency point.

How It Works

At each sweep frequency, the firmware multiplies the measured S-parameter by a phase rotation:

corrected = measured × e^(-j × 2π × frequency × delay)

This removes the linear phase slope caused by cable length. The result is as if you measured directly at the DUT without the intervening cable.

Set Electrical Delay

1. Go to DISPLAY > SCALE > E-DELAY
2. Choose S11 or S21 channel
3. Enter delay value in seconds (e.g., 1.5e-9 for 1.5 ns)

Tip

To estimate the delay for a known cable: divide the cable length by the speed of light times the velocity factor. For 30 cm of RG-58 (VF=66%): 0.3 / (3×10⁸ × 0.66) ≈ 1.5 ns.

Automatic Delay from Marker

A quick way to set electrical delay:

1. Connect the cable with an open or short at the far end
2. Display phase trace (S11 Phase format)
3. Adjust electrical delay until the phase trace is flat
4. The correct delay value removes the cable’s phase slope

Practical Uses

• De-embedding test cables: Remove phase effects of cables between VNA and DUT
• Viewing DUT phase response: See only the device’s contribution to phase shift
• Time domain preparation: Shifting the reference plane before enabling transform
• Antenna feed line compensation: View impedance at the antenna rather than at the radio

Shell Commands

# Set electrical delay per channel (in seconds)
edelay s11 1.5e-9     # 1.5 ns for S11
edelay s21 2.3e-9     # 2.3 ns for S21
edelay s11 0          # Clear S11 delay
edelay s21 0          # Clear S21 delay

Shell Commands

# Set scale per division for a trace
trace 0 scale 10      # Trace 0: 10 dB/div
trace 1 scale 45      # Trace 1: 45 degrees/div

# Set reference position (0-8)
trace 0 refpos 7      # Reference at position 7 (near top)
trace 2 refpos 4      # Reference at center

Scaling Examples

For Antenna SWR

Format: SWR
Scale: 0.5 or 1 per division
Reference Position: 0 (bottom)
Reference Value: 1.0

This shows SWR from 1:1 at the bottom.

For Return Loss

Format: LogMag
Scale: 10 dB/div
Reference Position: 8 (top)
Reference Value: 0 dB

Shows 0 dB at top, return loss increasing downward.

For Filter Passband

Format: LogMag
Scale: 1 dB/div
Reference Position: 8 (top)
Reference Value: 0 dB

Fine detail for passband ripple.

For Phase Response

Format: Phase
Scale: 45 deg/div
Reference Position: 4 (center)
Reference Value: 0 degrees

Shows +/-180 degrees centered on screen.

Multi-Trace Scaling

Each trace has completely independent scale, reference position, and reference value. This means you can display:

• Trace 0: S11 LogMag at 10 dB/div, reference at top
• Trace 1: S21 LogMag at 5 dB/div, reference at top
• Trace 2: S11 Smith at default scale
• Trace 3: S11 Phase at 45 deg/div, reference at center

When you adjust scale via the menu, the change applies only to the currently selected trace. Check the trace indicator (colored number in the legend) to confirm which trace is active before changing scale.

Common Mistakes

Adjusting the Wrong Trace

If scale changes don’t seem to affect the trace you’re looking at, you likely have a different trace selected. Tap the trace indicator to cycle through active traces.

Scale Too Large for the Data

If your trace appears as a flat line, the scale is too coarse. Use AUTO SCALE to fit the data, then adjust from there.

Reference Value Confusion

The reference value sets what value appears at the reference position line — it does not shift the data. Setting reference value to -20 dB with reference position at 7 means the -20 dB gridline is near the top of the screen.

Tips

Tip

Use AUTO SCALE after changing frequency range or connecting a new DUT, then fine-tune manually if needed.

Caution

Each trace has independent scale settings. Make sure you have the correct trace selected before adjusting scale.