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INVERTED L 40M ANTENNA
TECHNICAL DATA SHEET
Document Number: TM-INVERTED-L-4-001 Rev A Equipment: INVERTED L 40M ANTENNA Classification: UNCLASSIFIED — Amateur Radio / Field Use Date: 2026-05-24 Supersedes: None (initial issue)
RECORD OF CHANGES
| Change No. | Rev | Date | Description | By |
|---|---|---|---|---|
| 1 | A | 2026-05-24 | Initial formatted release | M. Martin |
Bands: 40M (7.0–7.3 MHz) Approach: Center-loaded vertical element with horizontal top-loading section, multiband capable Compaction: 50%
CHAPTER 1 — DESCRIPTION
Center-loaded vertical element with horizontal top-loading section, multiband capable
Special parameters: 35 ft vertical + 15 ft horizontal, loading coil at top junction, 50Ω feedpoint, broadband RX trap optional
CHAPTER 2 — TECHNICAL CHARACTERISTICS
| Parameter | Value |
|---|---|
| Frequency bands | 40M (7.0–7.3 MHz) |
| Feedpoint impedance | 50 Ω (nominal) |
| SWR target | < 2.0:1 |
| Efficiency | 70–95% |
| Gain | 0–12 dBi |
CHAPTER 3 — COMPONENTS AND MATERIALS
See detailed specification in inverted_l_40m_specs.csv
CHAPTER 4 — FABRICATION
- Review design parameters and dimensions
- Procure materials per component list
- Fabricate elements per specifications
- Install feedpoint connector
- Assemble and secure structure
- Verify physical dimensions match design
- Test with antenna analyzer (nanoVNA)
CHAPTER 5 — TESTING
Use nanoVNA and tinySA per FIELD_TESTING_WITH_INSTRUMENTS.md:
- Resonance: Find zero-reactance dip on Smith chart
- SWR: Measure across band, target < 2.0:1
- Impedance: Record R and jX at center frequency
- Spectrum: Use tinySA to verify radiation pattern
CHAPTER 6 — TROUBLESHOOTING
High SWR: Check physical dimensions, verify feed connection Frequency offset: Adjust element length or loading Impedance mismatch: Use antenna tuner or feed network
APPENDIX A — PARTS LIST
See inverted_l_40m_specs.csv
APPENDIX B — DIAGRAMS
See figures/ folder for antenna layout, circuit schematic, construction detail
APPENDIX C — NEC MODEL
See inverted_l_40m.nec for electromagnetic simulation
Navy Technical Manual Level — Generated with NEC2 modeling
Figures
