Monday, June 16, 2014

UHF Signal Amplifier for TV

This is the circuit diagram of UHF Signal Amplifier for television device. It uses single transistor 2SC3358 as the main signal amplifiication component.

Components List:

Rl, R2 = 1 KOhm
R3 = 2K2 Ohm
R4 = 470 Ohm
PI = 5 preset potentiometer
CI, C2, C6, C7 = 10 pF surface mount
C3 = 10 -, 35 V
C4, C8 = 1 nF disc
C5, C9 = 1 nF disc
LI, L2 = air core, 2 turns of 3mm diameter enamelled copper wire
L3, L4 = 10- choke or 10 turns of 0.2 mm diameter enamelled copper wire on a ferrite bead.
T1 = 2SC3358

PCB Design:

This circuit offers 10- to 15-dB gain from 400 to 850 MHz and is therefore eminently suitable for situations where the television signal is weak. Moreover, the filters can be adapted to the individual needs of users. Construction is simplicity itself if the ready-made PC board shown on the next page is used. The tracks should be tinned or silvered for optimum performance and long life.

The opening at the center of the board is intended to accommodate the transistor. This device has two emitter pins, both of which should be connected to ground. The drawings show that the board is divided into two by a small piece of tin plate, which should have a small cut-out for the transistor.

The input and output terminals are made from small cable clamps and M3 nuts and bolts. One side of disc capacitors C4, C5, C8, and C9 is soldered direct to the board.

Input and output capacitors, C1/C2 and C6/C7 respectively are surface-mount types. C1/C2/L1 form an input filter and C6/C7/L2 form an output filter. The value of the capacitors might have to be lowered to 3.9 pF to obtain the correct frequency range.

The amplifier can be housed in a watertight case and then mounted near the antenna at the top of the mast (if used). The power is obtained from a simple stabilized 12-V supply: a mains adapter with a 78L12 will do nicely. This can be kept indoors, of course.

The amplifier can be powered via the coaxial feeder cable, for which purpose a 10- to 100- choke is inserted in the supply line. Calibrating the amplifier is straightforward: set PI to the center of its travel and then adjust it for optimum picture quality. In practice, the collector current of the transistor is then 5 to 15 mA. This may be checked by temporarily replacing jump lead A by one suitable meter.

About RF Amplifier
An RF power amplifier is a type of electronic amplifier which is utilised to convert a low-power radio-frequency signal into a larger signal of significant power, usually for driving the antenna of a transmitter. It is usually optimized to have high efficiency, high output Power (P1dB) compression, good gain, good return loss on the input and output, and optimum heat dissipation.

The basic applications of the RF power amplifier include driving to another high power source, driving a transmitting antenna, microwave heating, and exciting resonant cavity structures. Among these applications, driving transmitter antennas is most well known.
More explanation about power audio amplifier can be found at
This is a demonstration about 01A RF Amplifier which is build used old tube component to amplify the signal.

Watch the video:

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