Shematic.net
More than Circuit EngineeringActive Folded Antenna (Aerial)
Active Folded Antenna (Aerial)Active antenna (pic.1) belongs to the group of devices in which parts of antenna are the elements of oscillatory circuit of amplifier. Such constructions are narrow-band and it is hard to put it right. If length of cable from antenna to the TV more than 15...20 m, better to place amplifier on antenna, because it is unnecessary to make large antenna. Amplification factor is multiplied due to a amplifier, the losses in a cable are compensate, on the input of TV set correlation gets better signal / noise.
Pic. 1. Active Antenna (Aerial)
Circuit.
Pic. 2. Active Antenna (Aerial)
Circuit with Plus Power Supply.
Pic. 3. Active Antenna (Aerial)
Circuit with Minus Power Supply.
On pic. 2 and pic. 3 nonselective one-stage amplifier (transistors КТ3101, КТ372) is mounted directly in a dipol.
Pic. 4. Amplifier Circuit and
Dipole Equivalent
Circuit (with Plus Power Supply).
Pic. 5. Amplifier Circuit and
Dipole Equivalent
Circuit (with Minus Power Supply).
On pic. 4 and pic. 5 represented equivalent circuit of such connecting, where: "Ekv" - equivalent circuit of dipol, "Tr" - equivalent circuit of quarter-wawe loop, that passes into a dipol and co-ordinate initial resistance of amplifier with resistance of cable. The quarter-wawe loop is wide-band.
Pic. 6. Amplifier Circuit Board
for
Meter Range.
Pic. 7. Amplifier Circuit Board
for
Decimeter Range.
On pic. 5 and pic. 6 represented circuit board of amplifiers. Placing of such type is added to influencing of external factors from which amplifier need to be protected (for example humidity).
added 18.07.07 01:06:28 | 
looked over 2000 times
