This type of eye fatigue or eye strain is sometimes known as computer vision syndrome. It affects about 50%-90% of computer workers. Some estimates say computer-related eye symptoms may be responsible for up to 10 million primary care eye examinations each year.
MAST MOUNTED PREAMPLIFIERS. Chapter Eight-TV ANTENNA-MOUNTED AMPLIFIERS. A mast or TV antenna-mounted amplifier (preamp) is used primarily to eliminate snow on the TV screen.Snow is actually electrical noise that is generated by the TV receiver and other electrical devices.he preamp itself is mounted on the TV antenna boom or on the mast as close to the TV antenna as possible. The power supply unit is mounted indoors. Power is supplied to the preamp unit through the transmission line.
If you put the same antenna inside a metal enclosure in the shape of a can, with one end of the can open, then the RF energy is directed out the open end of the can. This increases the gain of the antenna by 3 or more times in the direction that the open end of the can is pointing.