Delta and Tracking Markers

Delta markers display the difference between two marker positions, useful for measuring bandwidth, insertion loss changes, and frequency offsets.

Enable Delta Mode

1. Tap the screen to open the menu
2. Navigate to MARKER
3. Position at least two markers on the trace
4. Tap DELTA to enable delta mode

When delta mode is active, marker readings show the difference from the reference marker rather than absolute values.

Reference Marker

In delta mode, one marker serves as the reference (usually marker 1):

• Reference marker: Shows absolute values
• Delta markers: Show difference from reference

The reference marker is typically the lowest numbered active marker.

Note

Delta values are displayed with a delta symbol or +/- sign to indicate they are relative measurements.

Delta Display

In delta mode, the marker panel shows:

Reading	Description
Delta Frequency	Frequency difference from reference
Delta Magnitude	dB difference (for LogMag format)
Delta Phase	Phase difference in degrees

For example, if reference marker is at 100 MHz / -10 dB:

• A delta marker at 101 MHz / -13 dB shows: +1 MHz, -3 dB

Measuring Bandwidth

Use delta markers to measure filter bandwidth:

1. Place marker 1 at the filter center (peak or minimum)
2. Enable marker 2 and position at the -3 dB point (left side)
3. Enable marker 3 and position at the -3 dB point (right side)
4. Enable DELTA mode
5. Markers 2 and 3 show the frequency offset from center

The -3 dB bandwidth = (Marker 3 frequency) - (Marker 2 frequency)

Tip

For automatic -3 dB point finding, use the marker search functions (LEFT PEAK, RIGHT PEAK) described in the Marker Search guide.

Measuring Insertion Loss Change

1. Place reference marker at the frequency of interest
2. Place delta marker at a second frequency
3. The delta reading shows the loss difference between frequencies

This is useful for:

• Filter slope measurements
• Cable loss vs frequency
• Amplifier gain flatness

Tracking Markers

The NanoVNA-H supports marker tracking where the marker automatically follows a feature:

Peak Tracking

When enabled, the active marker automatically moves to the trace maximum or minimum:

1. Go to MARKER > TRACKING
2. Select MAX or MIN tracking
3. The marker now follows the peak/minimum as the sweep updates

This is useful for:

• Finding resonant frequency of tuned circuits
• Locating filter center frequency
• Tracking drifting signals

Disable Tracking

1. Go to MARKER > TRACKING
2. Select OFF to disable automatic tracking

Delta with Different Trace Formats

Delta values change meaning depending on the active trace format:

Trace Format	Delta Shows	Example
LogMag	Difference in dB	Reference: -10 dB, Delta: -3.2 dB → 3.2 dB more loss
Phase	Phase difference	Reference: +45°, Delta: -30° → 30° less phase
SWR	SWR difference	Reference: 1.5, Delta: +0.8 → SWR is 2.3
Smith (R+jX)	Impedance change	Reference: 50+j0, Delta: +25+j15 → Z is 75+j15
Delay	Time difference	Reference: 2.1 ns, Delta: +0.3 ns → 0.3 ns longer

Worked Example: Filter Bandwidth

Measuring a bandpass filter centered at 145 MHz:

1. Marker 1 at center: 145.0 MHz, S21 = -1.2 dB (insertion loss)
2. Enable delta mode
3. Marker 2 at left -3 dB point: delta reads -4.0 MHz, -3.0 dB
   • Frequency: 145.0 - 4.0 = 141.0 MHz
4. Marker 3 at right -3 dB point: delta reads +3.5 MHz, -3.0 dB
   • Frequency: 145.0 + 3.5 = 148.5 MHz
5. -3 dB bandwidth: 148.5 - 141.0 = 7.5 MHz

Practical Examples

Filter Insertion Loss Variation

1. Set sweep across filter passband
2. Place marker 1 at passband center
3. Place markers 2-4 at edges and corners
4. Enable delta mode
5. Read passband ripple from delta values

Antenna Bandwidth

1. Set SWR format on trace
2. Place marker 1 at minimum SWR point
3. Place marker 2 at 2:1 SWR point (left)
4. Place marker 3 at 2:1 SWR point (right)
5. Enable delta mode
6. Delta frequencies show the 2:1 SWR bandwidth

Comparing Two Frequencies

1. Place marker 1 at first frequency
2. Place marker 2 at second frequency
3. Enable delta mode
4. Read the difference directly

Shell Commands

Delta mode is controlled through the marker system. Set up markers via:

# Set up markers
marker 1 on
marker 2 on

# Position markers at specific indices
marker 1 50     # Reference at point 50
marker 2 150    # Delta marker at point 150

Caution

Delta values only make sense when comparing the same measurement type. Comparing LogMag to Phase gives meaningless deltas.

Limitations

Delta Only Applies to One Trace Format

Delta mode reads the value from the currently selected trace format. If you have multiple traces active (e.g., LogMag and Phase), the delta readout shows the difference for whichever trace is selected, not all of them simultaneously.

Reference Marker Cannot Be Changed

The reference marker is always the lowest-numbered active marker. You cannot designate an arbitrary marker as the reference. If you want marker 3 as the reference, disable markers 1 and 2.

Large Frequency Differences

Delta markers work best for measurements within the same sweep. If the reference and delta markers are at opposite ends of a wide sweep, interpolation effects and calibration edge behavior may affect accuracy.

Related Guides

• Marker Search — automatically find -3 dB points
• Using Markers — basic marker operations
• Smith Marker Formats — impedance readout options