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.
Some people who are infected with the influenza virus can actually transmit the illness before they begin to feel any symptoms. Most of the time, you will become contagious about 24 to 72 hours after contracting the influenza virus and remain that way for up to five days after the onset of symptoms. But children or people with compromised immune systems can be contagious to those around them for up to two weeks.