VHF receiver with PLL 2. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

VHF receiver with PLL. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / radio reception

Comments on the article

The radio receiver with a PLL offered to the attention of readers is designed to receive programs from broadcasting stations in the VHF band (65.8 ... 73 MHz). It is distinguished by a low supply voltage (6 V) and increased thermal stability.

(click to enlarge)

Schematic diagram of the radio frequency part of the receiver. 1. The signal received by the WA1 antenna goes to the input circuit L1C1C2, tuned to the middle frequency of the VHF band, and from it - through the R2C3 circuit - to the mixer. made on back-to-back diodes VD2, VD3. The local oscillator is assembled according to the multivibrator circuit with generation voltage stabilization by collector junctions of transistors VT1, VT2. The tuning frequency of the heterodyne circuit L2C8C9VD4 is two times lower than the frequency of the received signal. Over the range, the local oscillator is tuned by a variable capacitor C9. Auto-tuning is provided by a VD4 varicap matrix connected in parallel to the local oscillator circuit. The local oscillator voltage is supplied to the mixer through the R5C6 circuit. Resistor R5 reduces the ability to convert the mixer to the harmonics of the local oscillator. which significantly increases the stability of the mixer-local oscillator system when the latter is tuned in frequency.

The signal from the output of the mixer through the resistor R6 is fed to the input of a DC amplifier (UCA), made on transistors VT3, VT4. The initial bias voltage on the mixer diodes corresponds to the initial bias voltage at the input of the UPT and is provided by the diode VD1 and resistors R2. R4. The PLL loop is formed by resistor R12, through which the voltage from the output of the UPT is fed to the varicap array of the local oscillator. Zero potential on both matrix anodes is provided by resistor R8.

The stability of the frequency tracking system when the received signal level changes is ensured by a ladder filter formed by elements R7, C7, R11, C11 and the collector-base capacitance of the transistor VT3.

In addition to the PLL loop, the frequency tracking signal (and it is the modulating signal of the FM radio station) is fed through the R13C13 pre-distortion circuit to the input of the 3H amplifier.

Since the thermal stability of the voltage at the connection point of the resistors R2, R4 is determined by the transition of the silicon diode VD1, the mixer-local oscillator system is determined by the transitions of the diodes VD2, VD3 and transistors VT1, VT2, and the input voltage of the UPT is determined by the emitter transition of the transistor VT3, all voltages that determine the balancing of the UPT. when the temperature changes, they change proportionally in one direction, without introducing a significant unbalance into it.

Additional stability is provided, as already mentioned, by the resistor R5 and the OOS circuit (R14) in the UPT, which limits its voltage gain to 1000 ... 2000.

The device is mounted on the long-wave band of the VEF-201 receiver (Fig. 2).

VHF receiver with PLL
Fig. 2

During installation, MLT resistors and capacitors KT (C1, C2. C8) and KM (the rest) were used, C9 is a section of the KPE block available in the VEF-201 receiver. Coil L1 is wound on the body of the MLT-1 resistor with a resistance of more than 100 kOhm and contains 8 turns of PELSHO 0,5 wire, L2 - on the frame of the heterodyne circuit of the LV range (on its lower, not sectioned half) and consists of 9 turns of PELSHO 0.3 wire. The KT361B transistor can be replaced with a KT3107 with any letter index and a static current transfer coefficient h21e of at least 100, KT342B - with a KT3102 with h21e of at least 200. KT316B - with any of this series or KT368. Instead of KD503 diodes, you can use KD512A, KD514A. and instead of KD521V - any other diode of this series.

Setting up a receiver is easy. First, with the antenna turned off, resistor R4 is selected until a constant voltage of 2.5 ... 3 V is obtained at the output of the UPT. Then, by connecting the antenna and changing the distance between the turns of the L2 coil, the required tuning range of the local oscillator is set.

Within the boundaries of Sverdlovsk, the receiver steadily receives programs from all local VHF radio stations. With an excessively strong signal, the "jumping" effect of the radio station, observed due to a too large PLL holding band, could always be eliminated by reducing the length of the telescopic whip antenna. The current consumed by the receiver does not exceed 4,5 mA. operability in the VHF range is maintained when the supply voltage is reduced to 4,5 V.

Author: I. Pogartsev, Sverdlovsk; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section radio reception.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Portable Pet Hair Vacuum Cleaner 25.11.2022

Dyson has released a new tool to help make homes healthier for people who have pets.

The device is called the Dyson Grooming Kit for Pet. The new vacuum cleaner aims to provide better hygiene in homes with pets by removing hair from the room.

In fact, this is a cordless vacuum cleaner that cleans pet hair. The device is suitable for pets with medium and long hair.

Kit includes pet grooming tool, extension hose and quick coupler adapter. The care brush consists of 364 smooth bristles that can be used without turning on the vacuum cleaner. It can also be used to clean human hair.

The Dyson Grooming Kit for Pet is priced at $121.

Other interesting news:

▪ Flexible nano-thin touchscreen

▪ On the Benefits of Prayer

▪ Airships put out fires

▪ New stage of human evolution

▪ Computer of the future from Intel

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Electrician's tool. Article selection

▪ Article He who has ears, let him hear. Popular expression

▪ article What are anesthetics? Detailed answer

▪ article The structure of the legislation of the Russian Federation on labor protection

▪ article Frequency meter on a microcircuit. Encyclopedia of radio electronics and electrical engineering

▪ article Low-power power supply. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews