Trace Types

The NanoVNA-H firmware supports 30 distinct trace types, each providing a different view of the measured S-parameters. Trace types are organized by applicable channel (S11 reflection or S21 transmission).

Overview

Each trace type has associated metadata controlling its display:

Name: Short identifier shown on screen
Unit: Measurement unit symbol
Default Reference Position: Y-axis grid position for the reference level (0-based, NGRIDY=8)
Default Scale: Units per vertical division

S11 (Reflection) Trace Types

These trace types display measurements from the CH0 (S11) channel, showing reflection characteristics of the DUT.

Type	Name	Unit	Ref Position	Scale/Div	Description
`TRC_LOGMAG`	LOGMAG	dB	7 (top)	10 dB	Logarithmic magnitude of reflection coefficient
`TRC_PHASE`	PHASE	deg	4 (center)	90 deg	Phase angle of reflection coefficient
`TRC_DELAY`	DELAY	s	4 (center)	1 ns	Group delay
`TRC_SMITH`	SMITH	-	0	1.0	Smith chart (normalized impedance)
`TRC_POLAR`	POLAR	-	0	1.0	Polar plot of reflection coefficient
`TRC_LINEAR`	LINEAR	-	0	0.125	Linear magnitude of reflection coefficient
`TRC_SWR`	SWR	-	0	0.25	Standing Wave Ratio
`TRC_REAL`	REAL	-	4 (center)	0.25	Real part of reflection coefficient
`TRC_IMAG`	IMAG	-	4 (center)	0.25	Imaginary part of reflection coefficient
`TRC_R`	R	ohm	0	100 ohm	Resistance (real part of impedance)
`TRC_X`	X	ohm	4 (center)	100 ohm	Reactance (imaginary part of impedance)
`TRC_Z`	\|Z\|	ohm	0	50 ohm	Impedance magnitude
`TRC_ZPHASE`	Z phase	deg	4 (center)	90 deg	Impedance phase angle
`TRC_G`	G	S	0	10 mS	Conductance
`TRC_B`	B	S	4 (center)	10 mS	Susceptance
`TRC_Y`	\|Y\|	S	0	20 mS	Admittance magnitude
`TRC_Rp`	Rp	ohm	0	100 ohm	Parallel resistance
`TRC_Xp`	Xp	ohm	4 (center)	100 ohm	Parallel reactance
`TRC_sC`	sC	F	4 (center)	10 nF	Series capacitance
`TRC_sL`	sL	H	4 (center)	10 nH	Series inductance
`TRC_pC`	pC	F	4 (center)	10 nF	Parallel capacitance
`TRC_pL`	pL	H	4 (center)	10 nH	Parallel inductance
`TRC_Q`	Q	-	0	10	Quality factor

S21 (Transmission) Trace Types

These trace types work with both S11 and S21 channels, but some are specifically designed for S21 transmission measurements.

Universal Types (S11 and S21)

Type	Name	Unit	Ref Position	Scale/Div	Description
`TRC_LOGMAG`	LOGMAG	dB	7 (top)	10 dB	Logarithmic magnitude
`TRC_PHASE`	PHASE	deg	4 (center)	90 deg	Phase angle
`TRC_DELAY`	DELAY	s	4 (center)	1 ns	Group delay
`TRC_SMITH`	SMITH	-	0	1.0	Smith chart display
`TRC_POLAR`	POLAR	-	0	1.0	Polar plot
`TRC_LINEAR`	LINEAR	-	0	0.125	Linear magnitude
`TRC_REAL`	REAL	-	4 (center)	0.25	Real part
`TRC_IMAG`	IMAG	-	4 (center)	0.25	Imaginary part

S21-Specific Types

Type	Name	Unit	Ref Position	Scale/Div	Description
`TRC_Rser`	Rser	ohm	4 (center)	100 ohm	Series resistance (from S21)
`TRC_Xser`	Xser	ohm	4 (center)	100 ohm	Series reactance (from S21)
`TRC_Zser`	\|Zser\|	ohm	4 (center)	100 ohm	Series impedance magnitude
`TRC_Rsh`	Rsh	ohm	4 (center)	100 ohm	Shunt resistance (from S21)
`TRC_Xsh`	Xsh	ohm	4 (center)	100 ohm	Shunt reactance (from S21)
`TRC_Zsh`	\|Zsh\|	ohm	4 (center)	100 ohm	Shunt impedance magnitude
`TRC_Qs21`	Q	-	0	10	Quality factor (from S21)

Common Trace Types — Visual Reference

The four most-used trace formats. Each screenshot is captured directly from the NanoVNA-H LCD.

LOGMAG — Return loss or insertion loss in dB:

LOGMAG trace showing S11 and S21 magnitude from 100 to 200 MHz

SWR — Standing wave ratio for antenna tuning:

SWR trace showing standing wave ratio for S11

Smith Chart — Complex impedance on a normalized grid:

Smith chart display showing S11 impedance trace

Phase — Reflection or transmission phase in degrees:

Phase trace showing S11 phase angle across frequency

Trace Type Categories

Rectangular Grid Types

Most trace types display on a rectangular grid with frequency on the X-axis:

LOGMAG, PHASE, DELAY, LINEAR, SWR, REAL, IMAG,
R, X, Z, ZPHASE, G, B, Y, Rp, Xp,
sC, sL, pC, pL, Q,
Rser, Xser, Zser, Rsh, Xsh, Zsh, Qs21

Circular/Polar Grid Types

These types display on a circular grid:

SMITH: Normalized impedance on Smith chart (real axis 0-infinity, imaginary axis -j to +j)
POLAR: Complex reflection coefficient (magnitude 0-1, angle 0-360 deg)

Nano-Scale Types

These types use nano/pico unit scaling for input values:

DELAY (nanoseconds), sC, sL, pC, pL (nanofarads/nanohenries)

Display Format Strings

Each trace type has associated format strings for marker readout:

Type	Value Format	Delta Format	Example Output
LOGMAG	`%.2f dB`	`delta %.3f dB`	`-3.25 dB`
PHASE	`%.2f deg`	`delta %.2f deg`	`45.00 deg`
DELAY	`%.4F s`	`%.4F s`	`1.234 ns`
SWR	`%.3f`	`delta %.3f`	`1.500`
R, X, Z	`%.3F ohm`	`delta %.3F ohm`	`50.0 ohm`
G, B, Y	`%.3F S`	`delta %.3F S`	`20.0 mS`
sC, pC	`%.4F F`	`delta %.4F F`	`10.00 pF`
sL, pL	`%.4F H`	`delta %.4F H`	`100.0 nH`

The %F format applies automatic SI prefix scaling (k, M, G, m, u, n, p).

Trace Configuration

Each trace has the following configuration parameters stored in trace_t:

typedef struct trace {
  uint8_t enabled;       // 0=disabled, 1=enabled
  uint8_t type;          // TRC_LOGMAG, TRC_PHASE, etc.
  uint8_t channel;       // 0=S11, 1=S21
  uint8_t smith_format;  // Smith chart marker format (MS_LIN, MS_LOG, etc.)
  float scale;           // Units per division
  float refpos;          // Reference position (0-NGRIDY)
} trace_t;

Maximum trace count is 4 active traces (TRACES_MAX = 4), plus 1 stored trace (STORED_TRACES = 1).

Source Code Reference

Trace type definitions are located in:

Enum definition: nanovna.h lines 837-847
Trace info table: plot.c lines 564-596 (trace_info_list[])
Trace structure: nanovna.h lines 989-996