# NanoVNA Antenna Testing

## Overview

A **NanoVNA** (Vector Network Analyzer) is the essential tool for verifying antenna performance before deployment. It measures SWR (Standing Wave Ratio) and impedance - telling you how well your antenna is matched to the 50 Ω system and whether it is resonant at 915 MHz. A 10-minute NanoVNA check before mounting an antenna can save hours of troubleshooting range problems later.

## Models

<table id="bkmrk-modelscreenfrequency"><thead><tr><th>Model</th><th>Screen</th><th>Frequency Range</th><th>Price</th></tr></thead><tbody><tr><td>NanoVNA-H</td><td>2.8″</td><td>50 kHz - 1.5 GHz</td><td>~$30 - 50</td></tr><tr><td>NanoVNA-H4</td><td>4.0″</td><td>10 kHz - 1.5 GHz</td><td>~$50 - 70</td></tr><tr><td>NanoVNA-F</td><td>4.3″ (metal case)</td><td>10 kHz - 1.5 GHz</td><td>~$50 - 70</td></tr></tbody></table>

Kit includes: NanoVNA unit, calibration standards (Open/Short/Load), two SMA cables, USB-C charging cable.

## Five-Step Testing Procedure

### Step 1 - Initial Setup

1. Charge the NanoVNA via USB-C before first use.
2. Power on.
3. Set the frequency range: **START = 850 MHz**, **STOP = 950 MHz**.

### Step 2 - Calibration (Most Critical)

**Calibrate every session or any time you change the frequency range.** Calibration compensates for cable and connector losses - skipping it invalidates all measurements.

1. Navigate to **Menu → CAL → CALIBRATE**.
2. Connect the **OPEN** standard → select OPEN → wait for measurement.
3. Connect the **SHORT** standard → select SHORT → wait.
4. Connect the **LOAD** (50 Ω) standard → select LOAD → wait.
5. Save calibration to a slot (0 - 4).
6. Verify: reconnect LOAD → SWR should read **~1.0**, impedance **~50+j0 Ω**.

**Recalibrate when:** changing frequency range; moving to a significantly different temperature environment; switching to different cables.

### Step 3 - Configure Display

- Set **Trace 1** to **SWR**.
- Optionally set **Trace 2** to Smith Chart or R+jX for impedance detail.
- Add a **marker at 915 MHz**.

### Step 4 - Connect Antenna

- Connect antenna cable to **CH0 (Port 1)**.
- Use the shortest possible cable between the NanoVNA and antenna.
- Tighten connectors finger-tight only - do not over-torque SMA.
- **Check connector type:** LoRa antennas commonly use SMA or RP-SMA. These look identical but are not compatible - verify before connecting.

### Step 5 - Interpret Results

#### SWR Ratings

<table id="bkmrk-swrratingaction-1.0%E2%80%93"><thead><tr><th>SWR</th><th>Rating</th><th>Action</th></tr></thead><tbody><tr><td>1.0 - 1.5</td><td>Excellent</td><td>Deploy with confidence</td></tr><tr><td>1.5 - 2.0</td><td>Good - acceptable</td><td>Fine for most deployments</td></tr><tr><td>2.0 - 3.0</td><td>Marginal - some power loss</td><td>Investigate connector quality</td></tr><tr><td>3.0+</td><td>Poor - significant loss</td><td>Replace antenna or diagnose connector</td></tr></tbody></table>

#### Resonant Frequency

The **lowest SWR dip** on the sweep is the antenna's resonant frequency.

- Dip **at 915 MHz** - optimal
- Dip **below 915 MHz** - antenna is slightly long (resonates lower)
- Dip **above 915 MHz** - antenna is slightly short (resonates higher)

## Common Problems &amp; Diagnosis

<table id="bkmrk-symptomlikely-cause-"><thead><tr><th>Symptom</th><th>Likely Cause</th></tr></thead><tbody><tr><td>High SWR across entire 850 - 950 MHz band</td><td>Antenna tuned for 868 MHz (European band); damaged or loose connector; missing ground plane on whip antenna</td></tr><tr><td>SWR varies wildly / unstable reading</td><td>Loose connector; damaged cable - wiggle connections while watching display</td></tr><tr><td>Excellent SWR but poor range</td><td>SWR measures *impedance match only*, not gain. A perfectly matched 0 dBi antenna will outperform a mismatched 6 dBi antenna at short range, but not at distance. Evaluate antenna gain separately.</td></tr></tbody></table>

## PC Software: NanoVNA-Saver

**NanoVNA-Saver** is free, open-source software (Windows/Mac/Linux - search GitHub for "NanoVNA-Saver") that connects to your NanoVNA via USB and provides:

- Larger, higher-resolution graphs
- Data export (CSV)
- Smith chart display
- Touchstone (.s1p) file export for import into antenna modeling software
- Multi-antenna comparison - overlay sweeps from different antennas

Recommended for antenna selection decisions and documentation of deployed infrastructure antennas.

## Common Mistakes to Avoid

- **Skipping calibration** - all measurements are invalid without calibration
- **Calibrating at the wrong frequency range** - calibration is only valid for the range it was performed at; recalibrate if you change START/STOP
- **Testing indoors near metal objects** - nearby metal detuning antennas; test in the open or simulate the actual mounting environment
- **Using adapters without accounting for electrical length** - SMA adapters add a small but measurable electrical length; minimize adapter use
- **Confusing SMA and RP-SMA** - SMA has center pin on plug; RP-SMA has center pin on jack. Forcing mismatched connectors damages both.