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[TowerTalk] NVIS (not exactly towers, but HF)

To: towertalk <towertalk@contesting.com>
Subject: [TowerTalk] NVIS (not exactly towers, but HF)
From: jimlux <jimlux@earthlink.net>
Date: Mon, 8 Jun 2020 11:02:53 -0700
List-post: <mailto:towertalk@contesting.com>
I guess if you have a tower, you're not so interested in NVIS <grin>
Interesting paper (behind IEEE paywall unfortunately) in this month's Antennas and Propagation Magazine. The authors have a series of papers over the past few years of interest, looking at various performance factors.


P. J. Coetzee and W. P. du Plessis, "Performance Limiters of Near-Vertical-Incidence Skywave Propagation: A Scientific Approach," in IEEE Antennas and Propagation Magazine, vol. 62, no. 3, pp. 39-44, June 2020, doi: 10.1109/MAP.2019.2943313.


Abstract:
Near-vertical-incidence skywave (NVIS) propagation is defined as providing continuous coverage from nearly 0 km (just beyond the line of sight) to a couple hundred kilometers from the transmitter with no skip or dead zones. NVIS communications are especially effective during disaster-relief operations when infrastructure is severely damaged. The ability to accurately determine the performance limiters of NVIS propagation can help in the planning of high-frequency (HF) (3-30 MHz) emergency communication links. In the literature, widely varying radial distances (from as few as 50 to up to 160 or even 320 km) for the coverage attainable by NVIS propagation have been reported. It is very difficult to plan an NVIS link for homeland security or disaster relief when the published guidelines vary to such a degree. In this study, a scientific approach was utilized to determine the NVIS performance limiters for varying solar conditions, times of day, and geophysical locations.
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