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NVIS Propagation Ron Hranac, N0IVN. VHF and UHF simplex and repeater operation can provide generally reliable local and regional communications But these.

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Presentation on theme: "NVIS Propagation Ron Hranac, N0IVN. VHF and UHF simplex and repeater operation can provide generally reliable local and regional communications But these."— Presentation transcript:

1 NVIS Propagation Ron Hranac, N0IVN

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

3 Source: Line-of-Sight Propagation

4 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? NVIS Propagation

5 The solution? NVIS Near vertical incidence skywave RF propagation suited for close-in radio communications, typically in the 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 NVIS Propagation

6 Source: Ionospheric Propagation

7

8 Source: 300 mile radius coverage

9 Source: Dipole Radiation Pattern vs. Height

10 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 NVIS Frequencies

11 Source: Australian Government IPS Radio and Space Services North America Ionospheric Map

12 Source: Australian Government IPS Radio and Space Services Hourly Area Predictions (HAP) Chart

13 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 NVIS Antennas

14 “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 NVIS Antenna Height

15 “Near Vertical Incident Skywave (NVIS) Antenna” by Pat Lambert, W0IPL “NVIS - What it is and how to use it” by Patricia Gibbons, WA6UBE “Some Notes on NVIS Cloud Burners” by L.B. Cebik, W4RNL “Make A Quick, Easy, Cheap, NVIS Antenna for Roadside Operating” by D. W. Thorne, K6SOJ Australian Government IPS Radio and Space Services NVIS References


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