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K9AY LOOP 40M ANTENNA

TECHNICAL DATA SHEET

Document Number: TM-K9AY-LOOP-40-001 Rev A Equipment: K9AY LOOP 40M ANTENNA Classification: UNCLASSIFIED — Amateur Radio / Field Use Date: 2026-05-24 Supersedes: None (initial issue)

RECORD OF CHANGES

Bands: 40M (7.0–7.3 MHz) Approach: Directional receiving loop, tuned with variable capacitor for null rejection, non-radiating Compaction: 0%

CHAPTER 1 — DESCRIPTION

Directional receiving loop, tuned with variable capacitor for null rejection, non-radiating

Special parameters: 20 ft square loop, 1000 pF air-gap variable capacitor, cardioid null pattern, impedance step-up transformer

CHAPTER 2 — TECHNICAL CHARACTERISTICS

CHAPTER 3 — COMPONENTS AND MATERIALS

See detailed specification in k9ay_loop_40m_specs.csv

CHAPTER 4 — FABRICATION

1. Review design parameters and dimensions
2. Procure materials per component list
3. Fabricate elements per specifications
4. Install feedpoint connector
5. Assemble and secure structure
6. Verify physical dimensions match design
7. Test with antenna analyzer (nanoVNA)

CHAPTER 5 — TESTING

Use nanoVNA and tinySA per FIELD_TESTING_WITH_INSTRUMENTS.md:

1. Resonance: Find zero-reactance dip on Smith chart
2. SWR: Measure across band, target < 2.0:1
3. Impedance: Record R and jX at center frequency
4. 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 k9ay_loop_40m_specs.csv

APPENDIX B — DIAGRAMS

See figures/ folder for antenna layout, circuit schematic, construction detail

APPENDIX C — NEC MODEL

See k9ay_loop_40m.nec for electromagnetic simulation

Navy Technical Manual Level — Generated with NEC2 modeling

Figures