afu.tools
DEEN Sign in

Home › Measure an antenna

Measure an antenna

The browser talks to a LiteVNA, NanoVNA-V2 or NanoVNA-H directly and logs resonance, SWR, resistance, bandwidth and Q. With a tunable antenna you turn the knob and the page measures each time you stop; with a fixed one a single pass is enough.

Never connect it to an antenna that is being transmitted on. The first transmission on a nearby frequency destroys the input. Transmitter off, cable disconnected, then measure. And don't stand next to the antenna, your body pulls the resonance.

What's on the end of the cable?

Everything else follows from this: a tunable antenna is tracked across its whole tuning range, a fixed one is measured in one pass.

Type of antenna
Measurement range
Frequencies by hand
What you enter here applies. The band selection above is cleared.
Without this note nobody can tell later what was actually measured.
More settings
How far beyond the band edges to measure. Without a margin the sweep won't find a detuned antenna.
A dip counts as a resonance when it is deeper than −3 dB and at least 2 dB below the median of the sweep.
1 is fastest, up to 80 possible.

Connect the analyser

Pick the device, connect, carry on. Everything after this needs a device on the cable.

Device

In the port picker the LiteVNA is usually called "DEMO", the NanoVNA-V2 and NanoVNA-H both "STM32 Virtual ComPort". Once connected, the device display freezes; disconnecting gives it its controls back.

You need a LiteVNA 64 or 62, a NanoVNA-V2 (SAA2) or a NanoVNA-H / H4. V2 and H share the same USB ID but speak different protocols, so pick the right type here: the port picker can't tell them apart. The NanoVNA-H sweeps at most 401 points (original firmware: 101), and the page takes what the device offers; averaging means sweeping several times on it. The entry "show all ports" is meant for clones with a different ID; the protocol is then detected from the first sign of life.
Got a different VNA? Let us know, with maker, model and if possible a pointer to the protocol description. Maybe it can be added.

Accuracy

You can skip this step. A first look at resonance and SWR doesn't need it; if you need to trust R and X, go through it.

Calibration

The device uses the calibration slot loaded on it. That is only right if it matches your cable. A NanoVNA-H without a loaded slot measures raw until SOL has been recorded here.

See what the analyser sees

One sweep, nothing is saved. With a standard on the end of the cable it tells you whether the calibration fits.

Record your own correction

Screw the three standards onto the end of the cable one after the other. From them the page works out the error terms and corrects every following sweep.

Reference plane

SWR survives the cable, R and X don't: they come from the phase, and that rotates along the way. Using the delay, the page takes the cable out of the calculation. From a run this works without a standard.

Measure

0Sweep
—Dip / MHz
—Return loss / dB
—SWR
0/3Standstill
readyState

Result

Shown once the run has ended.

After the run you'll find the bands the antenna works on, its key figures, the curves and every measured point here.

What R, X and SWR mean on the Smith chart and how to match the antenna, you can try out in the Smith chart. It shows a measurement file (.s1p) from your analyser as a curve there.

Not connected yet.

Shared measurements

What others have measured with this page and chosen to show.

Nothing shared yet.