Don Honorio Ventura Technological State UniversityBicolor, Pampanga

College of Engineering and ArchitectureElectronics Engineering

Summary of Report

Group tree:Guevarra, Michelle Sunnee S.

Puno, Jerome

Asuncion, Jeryll M.

ISOLATION BY THE RF AMPLIFIER

RF stage separates the mixer from the antenna circuit.The pre-selector is tuned to only the radio frequencies within the selected channel.

2 Problems Solved:

1. Any interfering RF signal outside the channel that exists in the antenna circuit is attenuated by the RF stage.

2. The attenuation of the RF stage in the reverse direction, from the mixer to the antenna. This feature is very important in preventing the local oscillator signal, which is at the mixer input, from reaching the antenna.

Any oscillator radiation from the antenna is a source of interference to other equipment.

UHF TUNER

Older TV receiver have a separate UHF Tuner UHF Tuner is similar to the VHF Tuner but it has a higher frequencies in the

UHF Band Sometimes it doesn’t include RF stage because low-noise RF amplifiers for

the UHF band are costly

The mixer is generally a high frequency diode making the circuit passive, without amplification

Notice that the IF output of the UHF Tuner is not routed directly to the IF amplifier. Instead, the IF signal is fed to the VHF Tuner

TUNER FUNCTIONAL BLOCKS

(Fig.14-7)

This circuit has an antenna input combiner that mixes together all the received RF signals

VHF and UHF tuners are all in single tuner assembly, only one put is needed In selecting the antenna signal path , the band switch will enable and

disable the appropriate local oscillator RF amp and the mixer of the VHF tuner are converted to IF amplifiers when

in the UHF mode

(Fig.14-8)

Functional Blocks of Electronic Tuner that will tune the VHF and YHF TV broadcast channels along with all the mid-band, super-band, hyper-band CATV channels

The system’s memory may be a separate IC or part of the system micro controller

Older tuners are mechanical, known as rotary type.

Questions:

1. What is the relation of the hidden lines of the local oscillator going through the VHF / UHF input in the block diagram?

2. Elaborate the second problem in the Isolation by the RF Amplifier.3. Why does it need to detect either it is a VHF or UHF in the input combiner?