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A. Receiving Antenna
B. Tuning
C. Oscillator
D. Microphone Tool Sound (Loudspeaker)
E. Amplifier MF (Middle Frequency) Electric Current Source
F. Detector
G. Sound Amplifier
H. ...


A. Receiving Antenna
B. Tuning
C. Oscillator
D. Microphone Tool Sound (Loudspeaker)
E. Amplifier MF (Middle Frequency) Electric Current Source
F. Detector
G. Sound Amplifier
H. Final Brace

A six transistor radio receiver is also called a superheterodyne radio. Super means the most, high quality or better, hetero means various, more than one or more copies, and dyne means power. So a superheterodyne radio is a radio receiver consisting of complete parts, which can produce the best sound quality and high power or loud sound.

six transistor radio parts

There are four reasons why this type of superheterodyne radio was chosen to be studied and practiced, namely as follows.
1. Sensitive and sensitive, meaning that it is able to pick up radio frequencies even though they are small (weak) and located far away.
2. The frequency range is wider, meaning that it can capture a larger number of radio waves.
3. High power, meaning that it can produce a louder sound.
4. Easy to develop, meaning that almost all radio factories produce superheterodyne radios and are used by the general public. So that if there is a radio breakdown, we can fix it. It is different if we only study and practice straight radio which is no longer developed, then we will miss the development of technology.

In general, the parts of a six transistor radio set consist of:
1) receiving antenna,
2) tuning,
3) oscillator,
4) mixer,
5) amplifier / F / MF,
6) detector,
7) sound amplifier,
8) final amplifier,
9) sound tools, and
10) current source.

The relationship between the heterodyne radio parts can be described in a block schematic such as Figure 4.1.

radio block schematic

Do you know how a radio receiver works so that it can pick up radio waves and eventually be heard? To find out, you must understand the function of the ten parts of a six transistor radio. Here are the functions of all parts of the superheterodyne radio.

In addition to its function of receiving or capturing radio frequencies from space and forwarding these radio frequencies to the receiving plane, the receiver's antenna also functions to assist radio reception power. The antenna part is always offended by radio vibrations emanating from several transmitting stations.

Rod Antenna
Rod antennas are used in small radio receivers or portable (portable) radios. Because this antenna stands upright, signals from all directions can be received. Look at Figure 4.2 below!

rod antenna on radio

Ferrite Antenna
The ferrite antenna consists of a coil with a ferrite core. This antenna can pick up a signal strongly if the direction of the signal coming is perpendicular to the direction of the coil axis. In this antenna transistor radio is permanently installed, cannot be moved or rotated in its direction. To pick up the signal at maximum strength, the radio set must be positioned facing the correct direction.

Tuning is also called tuner loop. The functions, components, and how tuning works you learned in Chapter 1.

The oscillator (oscillator) serves to generate high vibrations. The high vibrations produced by this oscillator must be 455 kHz (kilohertz) greater than the transmitter frequency (FP) selected by the tuner loop section. This is a condition that must be met so that the radio can pick up radio waves. Thus in the mixer section (discussed next), there are two vibrations or frequencies to be mixed, each oscillator frequency (FO) and transmitter frequency (FP).

The main component of the oscillator is an oscillator spool consisting of a primary coil and a secondary coil. Between the two coils there is a ferrite which can be adjusted up and down because it has a thread. Setting this ferrite oscillator by turning on the ferrite groove using the tip of a flat screwdriver (-) which is made of non-metal material (a special screwdriver for crimping)

Figure 4.3 The shape of the oscillator spool and the oscillator symbol
The relationship between FO and FP is:
FO = FP + 455 k and FP = FO - 455 kHz
Example problem: A transmitter broadcasts at a frequency of 500 kHz. How many kHz frequency must be generated by the oscillator so that the transmitter frequency can be captured by the radio receiver?
Solution: Given: FP = 500 kHz
Wanted: FO =?

Answer: FO = FP + 455 kHz = 500 kHz + 455 kHz = 955 kHz So, the frequency generated by the oscillator is 955 kHz.

The mixer serves to mix the transmitter frequency (FP) with the oscillator frequency (FO). The result of the mixture of these two vibrations is a middle frequency with a weak frequency of around 450 kHz - 500 kHz. The intermediate frequency which is still weak needs to be amplified by the MF amplifier. Often times the oscillator is combined (combined) with a mixer and controlled by a transistor. The combined circuit of these two parts is called a converter. For more details, consider the mixer circuit in Figure 4.4 below.

the shape of the oscillator spool and the oscillator symbol

MF amplifier
The MF (middle frequency) or IF (intermediate frequency) amplifier functions to amplify weak intermediate frequencies into stronger intermediate frequencies. This amplification process is carried out by transistors TR4 and TR5.
Apart from the two transistors, the main components of this MF amplifier are three MF transformers, each colored yellow, white, and black. The results of the gain on the MF amplifier are then forwarded to the detector section.

mikser circuit

You learned about the functions, basic components and division of the detector circuit in Chapter 1.
The way the detector works starts from the sound waves in the form of a news signal fed to the audio amplifier. The next process, involves the parts of the detector circuit.

the process of reflection of the ionosphere layer

The filter in the detector circuit is useful for separating the 455 kHz frequency from the carrier frequency, so this filter is called a low pass filter. The rectifier circuit on the detector uses nonlinear components (such as diode tubes) or semiconductor components (such as germanium diodes or transistors).

There is no difference in the rectification of the waves in the detector circuit and in the power supply because the basic scheme of a detector circuit is no different from the basic circuit of a power supply.
Table 4.1 Differences and Similarities between Detector and Power Supply
No. Power Supply Detector
1. Its operating frequency is 455 kHz. Its operating frequency is 50 Hz - 60 Hz
2.Small working voltage (10V maximum) Large working voltage (as required)
3. Small current (in mA) Large current (as needed)
4. The input amplitude varies depending on the modulation. The input amplitude is fixed
5. At the output there is an alternating voltage - At the output there is an inverse voltage with a low frequency (news frequency) (the alternating voltage is very small, so it can be ignored).

Sound amplifier, its components, and functions you learned in Chapter 1.

The final amplifier serves to amplify the sound frequency in order to vibrate the membrane or loudspeaker paper. The rest of the final brace you learned in Chapter 1.
This section functions to convert the electrical vibrations of sound into audible sound vibrations. A loudspeaker has data in inches, ohms, and watts.
• Inch is the diameter of the loudspeaker width (1 inch = 2.54 cm).
• Ohm is the resistance value of the loudspeaker when used. Existing sizes for example 4 ohms, 8 ohms, and 16 ohms.
• Watt is the maximum power of the loudspeaker. Existing units for example 5W, 10W, up to hundreds of watts. You learned about the parts and how the loudspeaker works in Chapter 1.

The functions and parts of the source of electric current have also been discussed in the previous chapter of this book. Read it again and make sure you understand it.

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