ARES NVIS day is coming! ARRL Ohio section ARES organizes an event every year for stations to practice their NVIS skills. This is not a contest, instead it is an opportunity for Ohio amateur radio stations to practice using NVIS to contact other Ohio stations on the HF bands.
When is ARES NVIS Day?
DATE: Saturday April 23rd, 2022
Time: 10 AM – 4PM
Power: Up to but no more than 100 watts
Exchange: six-digit grid, power, and true—measured—signal report
What is NVIS?
NVIS stands for near vertical incidence skywave propagation. It is a type of radio wave propagation used mainly on the lower HF bands to communicate with nearby stations. Typically, NVIS is used on lower HF bands such as the 80 meter band. This will also work during daylight hours. Communications are typically within several hundred miles. NVIS signals are directed nearly vertical, refracted off of the ionosphere, then come back to the ground nearly vertical. This can give you communications in an emergency situation when repeaters may be down. It can allow you to communicate with a station that is on the other side of an obstruction such as mountains.
What antenna for NVIS?
Antennas used for NVIS do not have to be complicated. The most commonly used antenna for NVIS is a simple horizontally polarized 1/2 wavelength dipole. The most important part in making it an NVIS antenna is that it is hung less than a quarter wavelength above the ground. It is not uncommon for them to even be hung as low as 8 or 10 feet high. This gives it the nearly vertical propagation.
Here is a great Article from Rohde & Schwarz if you would like to take a more in-depth dive into radio wave propogation and NVIS.