Ryan Malloy
6f61e1c217
Reusable Astro component placed on 6 pages, cross-linking to nanovna-h.warehack.ing and nanovna-f.warehack.ing with cards matching the NanoVNAFamily visual style.
138 lines
3.5 KiB
Plaintext
138 lines
3.5 KiB
Plaintext
---
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title: Antenna Analysis
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description: Using mcnanovna to analyze antenna performance
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---
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import { Tabs, TabItem, Aside } from '@astrojs/starlight/components';
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import HardwareCards from '../../../components/HardwareCards.astro';
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This tutorial covers common antenna analysis tasks using mcnanovna.
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## Basic SWR and Impedance
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The most common antenna measurement is SWR (Standing Wave Ratio) and impedance at the feedpoint.
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Say: "Analyze my antenna from 144 to 148 MHz"
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Your assistant will:
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1. Run a sweep across the band
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2. Find the resonant frequency (minimum SWR)
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3. Calculate impedance at resonance
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4. Report bandwidth where SWR < 2:1
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**Example output:**
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```
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Resonant frequency: 145.2 MHz
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SWR at resonance: 1.15:1
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Impedance at resonance: 48.5 + j2.3 Ω
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Bandwidth (SWR < 2:1): 143.8 - 146.9 MHz (3.1 MHz)
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Return loss at resonance: -23.4 dB
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```
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## Finding Resonance
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For antennas with multiple resonances (like a multi-band antenna):
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Say: "Find all resonances from 1 to 30 MHz"
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This uses `analyze_s11_resonance` to find all points where the antenna is resonant.
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## Impedance Matching
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If your antenna doesn't match 50Ω, design a matching network:
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Say: "Design a matching network for 35+j25 ohms at 145 MHz"
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This uses `analyze_lc_match` to compute L-network solutions:
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```
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Solution 1: Series L (27 nH) + Shunt C (18 pF)
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Solution 2: Shunt C (12 pF) + Series L (42 nH)
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```
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## Antenna Types
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<Tabs>
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<TabItem label="Dipole">
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**Expected characteristics:**
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- Resonant impedance: ~73Ω
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- Narrow bandwidth
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- Figure-8 radiation pattern
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Say: "Analyze my dipole on 20m"
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</TabItem>
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<TabItem label="Vertical">
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**Expected characteristics:**
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- Resonant impedance: ~36Ω (ground-mounted)
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- Needs matching network or radials
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- Omnidirectional pattern
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Say: "Analyze my vertical on 40m"
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</TabItem>
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<TabItem label="Yagi">
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**Expected characteristics:**
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- Low impedance at feedpoint (~25Ω)
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- Narrow bandwidth
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- Directional pattern
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Say: "Analyze my Yagi from 144 to 148 MHz"
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</TabItem>
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<TabItem label="Loop">
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**Expected characteristics:**
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- Variable impedance based on size
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- High Q (narrow bandwidth)
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- Figure-8 pattern (small loop)
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Say: "Analyze my magnetic loop on 40m"
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</TabItem>
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</Tabs>
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## Troubleshooting Antennas
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### High SWR everywhere
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Possible causes:
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- Feedline not connected properly
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- Antenna not resonant in measurement range
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- Major construction problem
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What to check:
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- Verify feedline continuity
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- Widen the measurement range
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- Check physical dimensions
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### SWR dip but wrong frequency
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The antenna is resonant but not where you want it.
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- **Too low**: Antenna is electrically long → shorten
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- **Too high**: Antenna is electrically short → lengthen
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<Aside type="tip">
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For a dipole, each side is approximately λ/4 in length. At 145 MHz, that's about 51 cm per side.
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</Aside>
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### Good SWR but high reactance
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The antenna is resonant but not at 50Ω.
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Say: "Design a matching network for my measured impedance"
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### Narrow bandwidth
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High-Q antennas (small loops, loaded verticals) have narrow bandwidth. Options:
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- Accept it (tune for the portion of band you use)
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- Add loading to lower Q
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- Use an antenna tuner
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## Radiation Patterns
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For a quick analytical pattern based on antenna type:
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Say: "Show the radiation pattern for my dipole"
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This uses the S11 data to determine resonance and impedance, then generates an idealized 3D pattern.
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For measured patterns, see [3D Pattern Measurement](/tutorials/pattern-measurement/).
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<HardwareCards show="h" heading={false} />
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