Feddit.frThe Ultimate Guide to Affordable NVIS Comms (How to Build a Regional Off-Grid Radio Box)
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ProdigalFrogwww.youtube.com/watch?v=ZZxR-qtGH7c
www.youtube.com/watch?v=ZZxR-qtGH7c
Thanks for dropping the abbreviation. :) For those who want text:
https://en.wikipedia.org/wiki/Near_vertical_incidence_skywave
Summary for those in hurry: with NVIS, the ionosphere is your reflector, but you must use bloody low frequencies (e.g. 8 MHz). This will require loooong antennas (which may be horizontal, e.g. between trees) and will limit the data rate considerably. Overcrowding of the narrow range of good frequencies may occur if it becomes popular.
Linking this with some sound modem to transmit text data, ideally with some automatic repetition to remove errors, will probably be much nicer to communicate with. But cool concept overall.
What makes me worry is the size of the “reflector”. I wonder what symbol rate it is possible to get if the “reflector” is literally everywhere above you - the time delay between start of reflection and end of reflection might be considerable.
I found a resource with practical advise about using NVIS, including using meteorological data (ionograms) to determine the best frequency, antenna diagrams and such.
https://www.ipellejero.es/hf/NVIS/english.php
Excellent info, thanks for digging into that and sharing! :)
Anyone know how this compares to the mesh network?
If by Mesh Network you mean Meshtastic, they have very different use-cases.
Meshtastic requires regular nodes/repeaters within its somewhat short range to be effective (putting repeater stations atop hills or mountains can drastically extend that effective range), it also exclusively operates via text, not audio.
NVIS is just a small long-range portable radio that bounces radio waves directly off the ionosphere which is reflected in a circular radius of 150 to 300 miles from the transmitting antenna, and is not reliant on being atop mountains to attain that range due to the reflected bouncing. The video gives details on how it is generally used.