Production of TV antenna amplifiers ----- RF AMPLIFIER

Keywords: production of TV antenna amplifier Cable TV has not yet entered the net user, watching TV shows, there is also a TV antenna, here is an amplifier suitable for indoor TV antennas, which is simple, but the use is good. 1. Circuit principle The circuit of the indoor TV antenna amplifier is shown in Figure 1. It consists only with one ultra-high frequency triode. This amplifier is powered by G1 and G2 dual power supply. It is characterized by high frequency communication. The circuit is a common-emitted electrode circuit, but is a common base circuit for a DC channel. Therefore, this amplifier has a high voltage gain, but the noise is small. Also, because the power supply is divided into two groups, the B, E junctions of the triode do not affect each other, so there is a good isolation in the input of the circuit and the output of the circuit effectively improve the operating frequency of the circuit, guarantee A sufficient frequency band width, the single-stage amplifier gain can reach 8 dB, if the receiving point is far from the television station, can assemble the two-stage amplifier, the gain can reach 15 dB or more. During the level of level, when assembled two-stage amplification, it will not produce severe mismatch or self-excited. The input of the amplifier, the output feeder uses a 75Ω coaxial cable, so it can match the port of the TV antenna and the TV. 2. Component selection and production The Vt uses 3dG141, 3DG30C, 3DG30D, 3DG80, 2G911 type silicon NPN ultra-high frequency triode, requiring FT ≥ 600 MHz, β≥100. In addition to the three extraction of C, B, E, there are quadrants that take out the foot, the housing grounding, and the attachment should be taken away. Electrical resistance uses RTX-1/8 W-type carbon film resistors, and capacitors are CC1 ultra high frequency porcelain dielectric capacitors. Inductance L1, L2 requires self-made, with φ0.51mm enamel lines around 20 turns on a drill bit of 3.5 mm, and removes it. Power G1 and G2 are used in two batteries. Fig. 2 is a printing circuit board of this unit. The printed circuit board size is 55 × 25 mm. The printed plate should be made of a small epoxy resin, a high-frequency medium, and a large-scale grounding method. At the time of installation, each component leads should be cut shortly as possible, and the hood of the triode should be embedded in the circular hole of the printed circuit board, and the four leaders are welded in the reverse surface in the reverse surface. The printed board is surrounded by about 15 mm of copper or tin plated iron, and is soldered, and the upper and lower is sealed, sealed into a metal case (see Figure 3) to prevent interference of the external clutter signal. Input, output lines are taken from the box with a 75Ω coaxial cable. The plastic power cord is then taken from the side hole, and the power supply can be reliably operated.