Questions tagged [nvis]

Near Vertical Incidence Skywave refers to (normally HF) signals being radiated nearly vertically from the antenna, then reflected in the ionosphere resulting in an almost circular transmission coverage pattern. It is achieved by placing the antenna at low height and is commonly used for near-range communications on the lower HF bands, particularly 3.5 MHz.

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1 answer
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Where to begin with SDR?

I want to make a ground to ground non-line-of-sight (NLOS) data link. As I understand SDRs are perfect for this because I can specify frequency, bandwidth, channel size, etc., making it suitable for ...
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1 vote
2 answers
250 views

What is the minimum height required for a 60 meter NVIS antenna?

Various answers include 1/8th of the wavelength all the way down to 1/10th, but would 1/15th or even 1/20th of the wavelength be sufficient for a 60 meter (5 MHz) horizontal NVIS antenna?
2 votes
2 answers
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Does a NVIS antenna have to be exactly below the maximum NVIS frequency to have NVIS characteristics?

For example if the maximum NVIS frequency is 5 MHz in a given region, would a NVIS antenna have to be resonant at less than 5 MHz to have NVIS propagation characteristics or can it be slightly above ...
1 vote
1 answer
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Recommendations for Antennas installation with Steep slopes

I have a property that I am trying to figure out the right antenna setup for. Transmission Goals North of this property is 900 miles to communicate 80M or 40M. Also want to communicate to another ...
5 votes
4 answers
2k views

Can a vertical antenna be used for NVIS?

I know that verticals are normally chosen for their low angles of radiation without obscene heights, but I'm not especially interested in DX and am primarily looking for local coverage via NVIS. I've ...
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6 votes
1 answer
12k views

How to determine antenna height for given HF frequency and coverage radius?

I'm planning on setting up a low-HF antenna for near to mid-range contacts. In my particular case, ideally I would like to be able to cover a radius of approximately 1000-1200 km with good ...
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