APPLICATIONS Horn antennas are widely used as satellite dishes and radio telescopes. Antennas 6 2. PARABOLIC ANTENNAS A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves.
Flu (influenza). Flu is usually infectious a day before symptoms start and remains infectious for about five to six days. Children and people with lowered immune systems may be infectious for a few days longer.
Influenza's incubation period is 1-4 days with 2 days being the most common for showing symptoms. There are many viruses that cause cold and flu symptoms that are not the common cold or influenza. If you were exposed to one of those it may take up to 7 days before symptoms appear.