Smith Chart Marker Formats

When a trace is displayed in Smith chart mode, markers can show values in different formats. The NanoVNA-H supports 13 Smith chart marker formats, organized by applicable channel.

Format Overview

Each Smith marker format determines how the complex S-parameter value at the marker position is converted to displayed values.

Format ID	Name	Display Format	Description
MS_LIN	LIN	0.85 +45.0 deg	Linear magnitude and phase
MS_LOG	LOG	-1.4 dB +45.0 deg	Logarithmic magnitude and phase
MS_REIM	Re + Im	0.60+j0.60	Real and imaginary parts
MS_RX	R + jX	150+j100 ohm	Resistance and reactance
MS_RLC	R + L/C	150 ohm 100nH	Resistance and reactive component
MS_GB	G + jB	6.67+j4.44 mS	Conductance and susceptance
MS_GLC	G + L/C	6.67 mS 100nH	Conductance and reactive component
MS_RpXp	Rp + jXp	225+j150 ohm	Parallel R and X
MS_RpLC	Rp + L/C	225 ohm 100nH	Parallel R and reactive component
MS_SHUNT_RX	R+jX SHUNT	50+j25 ohm	Shunt R and X (S21)
MS_SHUNT_RLC	R+L/C SH..	50 ohm 10nH	Shunt R and reactive (S21)
MS_SERIES_RX	R+jX SERIES	50+j25 ohm	Series R and X (S21)
MS_SERIES_RLC	R+L/C SER..	50 ohm 10nH	Series R and reactive (S21)

S11 Smith Formats

For S11 (reflection) measurements, the following marker formats are available:

Polar

MS_LIN - Linear

Displays the reflection coefficient as linear magnitude and phase angle.

Format: %.2f +/- %.1f deg Example: 0.85 +45.0 deg

MS_LOG - Logarithmic

Displays the reflection coefficient as logarithmic magnitude (return loss) and phase angle.

Format: %.1f dB +/- %.1f deg Example: -1.4 dB +45.0 deg

MS_REIM - Real + Imaginary

Displays the reflection coefficient as complex number (real and imaginary parts).

Format: %F +/- j%F Example: 0.60+j0.60

Impedance

MS_RX - Resistance + Reactance

Displays impedance as resistance and reactance (series model).

Format: %F +/- j%F ohm Example: 150+j100 ohm

MS_RLC - Resistance + L/C

Displays resistance and automatically calculates the reactive component as inductance or capacitance based on sign.

Format: %F ohm %F H/F Example: 150 ohm 100nH (inductive) or 150 ohm 100pF (capacitive)

MS_RpXp - Parallel R + X

Displays parallel equivalent impedance.

Format: %F +/- j%F ohm Example: 225+j150 ohm

MS_RpLC - Parallel R + L/C

Displays parallel resistance and reactive component as L or C.

Format: %F ohm %F H/F Example: 225 ohm 150nH

Admittance

MS_GB - Conductance + Susceptance

Displays admittance as conductance and susceptance.

Format: %F +/- j%F S Example: 6.67+j4.44 mS

MS_GLC - Conductance + L/C

Displays conductance and reactive component calculated as L or C.

Format: %F S %F H/F Example: 6.67 mS 100nH

S21 Smith Formats

For S21 (transmission) measurements on the Smith chart, specialized formats calculate component values from the insertion loss:

Shunt Model

MS_SHUNT_RX - Shunt R + jX

Calculates shunt impedance from S21 transmission coefficient.

Format: %F +/- j%F ohm Example: 50+j25 ohm

The shunt impedance is calculated assuming the DUT is a shunt element between 50 ohm source and load.

MS_SHUNT_RLC - Shunt R + L/C

Displays shunt resistance and reactive component as inductance or capacitance.

Format: %F ohm %F H/F Example: 50 ohm 10nH

Series Model

MS_SERIES_RX - Series R + jX

Calculates series impedance from S21 transmission coefficient.

Format: %F +/- j%F ohm Example: 50+j25 ohm

The series impedance is calculated assuming the DUT is a series element between 50 ohm source and load.

MS_SERIES_RLC - Series R + L/C

Displays series resistance and reactive component as inductance or capacitance.

Format: %F ohm %F H/F Example: 50 ohm 10nH

Format Selection by Channel

The available Smith marker formats depend on the trace channel:

S11 Channel Formats

MS_LIN, MS_LOG, MS_REIM, MS_RX, MS_RLC, MS_GB, MS_GLC, MS_RpXp, MS_RpLC

S21 Channel Formats

MS_LIN, MS_LOG, MS_REIM, MS_SHUNT_RX, MS_SHUNT_RLC, MS_SERIES_RX, MS_SERIES_RLC

L/C Calculation Logic

For formats that display reactive components as L or C:

1. Positive reactance (X > 0): Calculated as inductance

   • L = X / (2 * pi * frequency)

2. Negative reactance (X < 0): Calculated as capacitance

   • C = -1 / (2 * pi * frequency * X)

The displayed symbol changes automatically:

• Inductance shown with H suffix (scaled to nH, uH, mH)
• Capacitance shown with F suffix (scaled to pF, nF, uF)

Menu Access

Smith marker formats are accessed through:

Menu Path: MARKER > SELECT MARKER > Select marker > OPERATIONS > SMITH FORMAT

Or for each channel:

• S11: DISPLAY > FORMAT S11 (REFL) > SMITH then touch marker info area
• S21: DISPLAY > FORMAT S21 (THRU) > SMITH then touch marker info area

Data Structure

The marker Smith format is stored per-trace in the trace_t structure:

typedef struct trace {
  uint8_t enabled;
  uint8_t type;
  uint8_t channel;
  uint8_t smith_format;  // MS_LIN, MS_LOG, MS_RX, etc.
  float scale;
  float refpos;
} trace_t;

Source Code Reference

Smith marker format definitions are located in:

• Enum definition: nanovna.h line 882
• Format info table: plot.c lines 598-613 (marker_info_list[])
• S11/S21 format masks: nanovna.h lines 886-887