No, a NanoVNA is not a spectrum analyser, although the two instruments are related and can complement each other. For amateur radio astronomy, they serve quite different purposes.
1. NanoVNA — Vector Network Analyser (VNA)
Measures how radio-frequency signals behave in circuits and antennas.
- Antenna resonance and SWR
- Impedance and matching
- Cable loss and return loss
- Filter response
It generates its own test signal and measures what happens to it.
2. Spectrum analyser
Shows the strength of signals arriving at its input across a range of frequencies.
- Identifies signals at particular frequencies
- Measures signal strength and bandwidth
- Reveals interference and unwanted emissions
- Displays noise and spectral peaks
It is useful for examining signals received by an antenna.
What is the difference for radio astronomy?
| Task | NanoVNA | Spectrum analyser |
|---|---|---|
| Test antenna resonance | Excellent | Limited |
| Measure antenna impedance | Excellent | Generally no |
| Find interference | Not its normal function | Excellent |
| Examine the 1420 MHz hydrogen line | No, not directly | Yes, with suitable frequency coverage and sensitivity |
| Measure received radio spectrum | No, not normally | Yes |
One important qualification: some NanoVNA models have a frequency range extending to around 3 GHz or higher, but that does not make them spectrum analysers. They are designed primarily to measure network parameters, not to analyse signals received from the sky.
For your radio astronomy work, a suitable SDR with spectrum-analysis software can be a more economical starting point for examining received signals. For the 1420 MHz hydrogen line, you would need an SDR and antenna system capable of operating at that frequency, with sufficient sensitivity and frequency stability.
A NanoVNA would still be valuable for checking the antenna, feed cable and filters in that system.