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NVIS Propagation

NVIS Propagation. Ron Hranac, N0IVN. NVIS Propagation. VHF and UHF simplex and repeater operation can provide generally reliable local and regional communications But these modes are limited to line-of-sight!. Line-of-Sight Propagation. Source: http://www.ycars.org. NVIS Propagation.

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NVIS Propagation

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  1. NVIS Propagation Ron Hranac, N0IVN

  2. NVIS Propagation • VHF and UHF simplex and repeater operation can provide generally reliable local and regional communications • But these modes are limited to line-of-sight!

  3. Line-of-Sight Propagation Source: http://www.ycars.org

  4. NVIS Propagation • What happens if there is no repeater coverage available, and VHF/UHF simplex doesn’t work because of terrain obstructions or distance? • Is there an option for regional or statewide radio communications?

  5. NVIS Propagation • The solution? NVIS • Near vertical incidence skywave • RF propagation suited for close-in radio communications, typically in the 50-300 miles range • Ideal for regional or statewide communications in the MF and HF spectrum • Works well in rugged terrain where line-of-sight communications is difficult or impossible

  6. Ionospheric Propagation Source: http://www.radio-electronics.com

  7. Ionospheric Propagation

  8. 300 mile radius coverage Source: http://www.mapquest.com

  9. Dipole Radiation Pattern vs. Height Source: http://www.moonraker.com.au

  10. NVIS Frequencies • Amateur bands in the lower part of the HF spectrum • 75 meters/80meters • 60 meters • 40 meters • In Colorado, 80 meters and 60 meters are likely to provide the most reliable NVIS communications

  11. North America Ionospheric Map Source: Australian Government IPS Radio and Space Services http://www.ips.gov.au/HF_Systems

  12. Hourly Area Predictions (HAP) Chart Source: Australian Government IPS Radio and Space Services http://www.ips.gov.au/HF_Systems

  13. NVIS Antennas • Full-size half-wave dipole • Reduced-length half-wave dipole (that is, trapped or inductively loaded) • Multi-band dipole • End-fed random wire • Full- or half-wave square • Dual Hamstick dipole or Buddipole

  14. NVIS Antenna Height • “The Near Vertical Incident Skywave (NVIS) antenna is a half-wave dipole antenna mounted not over 1/8th wave above ground (at the highest operating frequency). While 1/8th wave works reasonably well, better coverage is obtained if the antenna is mounted at about 1/20th wavelength above ground. A second advantage of lowering the antenna to near 1/20th wavelength is a lowering of the background noise level.” • Pat Lambert, W0IPL

  15. NVIS References “Near Vertical Incident Skywave (NVIS) Antenna” by Pat Lambert, W0IPL http://www.w0ipl.com/ECom/NVIS/nvis.htm “NVIS - What it is and how to use it” by Patricia Gibbons, WA6UBE http://www.tactical-link.com/field_deployed_nvis.htm “Some Notes on NVIS Cloud Burners” by L.B. Cebik, W4RNL http://www.cebik.com/wire/cb.html “Make A Quick, Easy, Cheap, NVIS Antenna for Roadside Operating” by D. W. Thorne, K6SOJ http://www.emcomm.org/projects/nvis.htm Australian Government IPS Radio and Space Services http://www.ips.gov.au/HF_Systems

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