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NVIS, Another Look

NVIS, Another Look. Fixed Installation Tri-Band. Tom Sanders, W6QJI Ed Bruette, N7NVP. Near Vertical Incident Skywave. Cloud Warmer. What is NVIS?. Propagation Theory. NVIS Effect. 300 Mile Coverage. 5/8 Wave 75 Meter Vertical Radiation Pattern. Propagation Considerations.

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NVIS, Another Look

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  1. NVIS, Another Look Fixed Installation Tri-Band Tom Sanders, W6QJI Ed Bruette, N7NVP

  2. Near Vertical Incident Skywave Cloud Warmer What is NVIS?

  3. Propagation Theory

  4. NVIS Effect

  5. 300 Mile Coverage

  6. 5/8 Wave 75 Meter Vertical Radiation Pattern

  7. Propagation Considerations • “D” layer losses • Ionospheric scattering for vertical propagation • Importance of critical frequency

  8. 75 Meter SWR

  9. Bandwidth 75 Meters • 4005 – 1.5:1 • 3950 – dip • 3875 – 1.5:1

  10. 75 Meter Vertical Radiation Pattern

  11. 75 Meter Current Distribution

  12. 60 Meter SWR

  13. Bandwidth 60 Meters • 5390 – 1.5:1 • 5360 – dip • 5317 – 1.5:1

  14. 60 Meter Vertical Radiation Pattern

  15. 60 Meter Current Distribution

  16. 40 Meter SWR

  17. Bandwidth 40 Meters • 7295 – 1.5:1 • 7245 – dip • 7225 – 1.5:1

  18. 40 Meter Vertical Radiation Pattern

  19. 40 Meter Current Distribution

  20. Dual Band • Yes; you can remove the 60 Meter elements!

  21. 75 Meter SWR

  22. 75 Meter Vertical Radiation Pattern

  23. 40 Meter Dual Band SWR

  24. 40 Meter Vertical Radiation Pattern

  25. Omni Pattern

  26. Feed Point Impedance vs. Height

  27. Depth of Current Penetration

  28. Where is your RF ground?

  29. How It Went Together • Materials • Construction • Modifications

  30. Parts List • 1 - Feed point - 50 Ohm • #14 insulated stranded wire – 280’ • 3 - ½” x 10‘ PVC cut to length • 2 – Insulators • Tie wraps • 3/16” rope cut to length • Coax to the shack

  31. Spreader Lengths • 2 – 17” Next to center insulator • 2 – 34” 2nd from center insulator • 2 – 50.5” End of 40 M element • 2 – 25.25” End of 60M element • Another spreader could be used between the center insulator and the end of the 40M element

  32. Element Lengths • 75 Mtr legs = 57.33 ft • 60 Mtr legs = 45.4 ft • 40 Mtr legs = 34.25 ft • Prune these lengths to meet your ground conditions

  33. 40 Meter Tension

  34. Tensioning method for 40M

  35. Spreader keepers

  36. 60 Meter tension UV resistant line

  37. 60 Meter Tension

  38. Beamwidth • 75 Mtrs 38 deg. To 142 deg. • 60 Mtrs 36.5 deg To 143.5 deg. • 40 Mtrs 34 deg. To 146 deg.

  39. Night Time Ionosphere (300 mi.)

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