Regenerative VHF-FM radio receiver. Scheme, description

Free technical library

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

Regenerative VHF-FM radio receiver. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / radio reception

Comments on the article

Now a simple VHF-FM broadcast receiver has ceased to be something that requires special measuring instruments and solid knowledge of this issue to set up. Many different microcircuits like the "legendary" K174XA34 did their job, and the manufacture of a pocket VHF-FM receiver became available to the most novice radio amateur. Some circuits, especially on assemblies like KXA058, are even simpler than many direct amplification receivers that were so popular in past years in terms of the simplicity of achieving the final result. Perhaps this is good - a novice radio amateur should be allowed to immediately get a positive result from his work. After all, one or two failures at the very beginning of your "creative life" can flatly discourage any desire to continue to engage in amateur radio.

And, nevertheless, there are many outwardly simple schemes, but intended for more experienced comrades, who usually do them not for the sake of quickly obtaining a positive result, but for the sake of "sports interest", in order to understand from their own experience all the nuances of this seemingly , simple scheme.

This regenerative VHF-FM broadcast receiver is one of such schemes. Therefore, if you are a beginner radio amateur, and this receiver didn’t work for you on the first try, don’t be upset, it may not work on the second attempt, and even on the third, fourth ... The schematic diagram of the receiver is shown in the figure. It consists of a regenerative detector on a VT1 transistor and a three-stage VLF, respectively, on VT2, VT3, VT4. Power source - one element with a voltage of 1,5V. Load - on the headphones from the audio player.

Regenerative VHF-FM radio receiver

Typically, regenerators are used in simple AM receiver circuits. In this case, in order to be able to detect FM, the receiver is tuned to one of the slopes of the radio station band, so that the frequency change caused by frequency modulation leads to receiver detuning and, as a result, a change in the signal level at the detector output.

The operating mode of the regenerative detector on VT1 is set by a variable resistor R1, which changes the bias voltage at the base of the transistor. Setting the position of R1, which provides the best reception, can vary significantly for different radio stations operating in different parts of the range and with different powers (or different degrees of remoteness).

The AF voltage is removed from the resistor R2 connected in series with the collector circuit of the transistor. Through the inductance L2, the AF voltage is supplied to the three-stage amplifier VT2-VT4, made according to the usual resistive circuit with a common emitter. Capacitor C6 suppresses high-frequency noise at the output of the last stage.

The L1 coil is frameless, first it is wound on a mandrel with a diameter of about 5-6 mm (thin ballpoint pen), then, having cut the conclusions, it is removed. The coil, for operation in the range of 87-108 MHz, must contain 8 turns of PEV 1,0 wire (or about this diameter). It must be stretched, initially, along a length of 12-13 mm (in the future, the length of the winding will need to be clarified when adjusting).

The tuning organ is a ceramic tuning capacitor C1.

Variable resistor R5 serves as a volume control. Initially, it must be set to the maximum volume position.

The antenna is a piece of mounting wire 20-40 cm long. It should be noted that powerful (or close) stations are received without an antenna.

Establishment. Set the resistor R1 to the extremely low position (R5 also, to the extremely low position). Gradually turn R1 until there is a sharp increase in noise in the headphones. Then, very carefully and slowly turn R1 in the same direction until the noise level decreases. Try to tune the receiver to the station with capacitor C1. When you first tune into a station, its sound can be very distorted, almost unintelligible. At the same time as adjusting C1 within small limits, very slowly, within small limits, adjust R1 in both directions until an undistorted reception with a low noise level and sufficient loudness is observed.

Since the design is experimental, the installation is made voluminous, on the tracks of the dismantled printed circuit board from the old TV.

Author: Gorchuk N.V.

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

DNA turned into logic gates 28.03.2019

A group of scientists led by researchers from the California Institute of Technology has been able to take a small but significant step in the development of arbitrarily programmable chemical computers. As basic computing elements in such systems, DNA sets are used, which, by their nature, have the ability to self-organize and grow. All that is needed to run DNA-based computing systems is warm brackish water, a DNA-encoded growth algorithm, and basic standard sets of DNA sequences.

So far, "calculations" with DNA have been carried out strictly using any one sequence. For arbitrary calculations, the existing methods were not suitable. Scientists from Caltech (Caltech) were able to overcome this limitation and presented a technology that can execute arbitrary algorithms using one basic set of conditionally logical DNA elements and a sample of 355 basic DNA sequences responsible for the "calculation" algorithm - analogous to computer instructions. A logical "seed" and a set of "instructions" are introduced into the saline solution, after which the calculation begins - the assembly of the sequence.

The basic element or "seed" is a DNA convolution (DNA origami) - a nanotube 150 nm long and 20 nm in diameter. The structure of the "seed" remains practically unchanged regardless of the algorithm that will be calculated. The periphery of the "seed" is formed in such a way that the assembly of DNA sequences starts at its end. A growing strand of DNA is known to be assembled from sequences that match the proposed sequences in terms of molecular structure and chemical composition, and not randomly. Since the periphery of the "seed" is represented in the form of six conditional valves, where each valve has two inputs and two outputs, DNA growth begins to obey a given logic (algorithm) which, as already mentioned above, is represented by a given set of DNA sequences placed in a solution of 355 basic options.

Scientists in the course of experiments have shown the possibility of executing 21 algorithms, including counting from 0 to 63, choosing a leader, determining division by three and others, although everything is not limited to these algorithms. The calculation process proceeds step by step as the DNA strands grow on all six outlets of the "seed". This process can take from one to two days. The production of "seed" takes from one to two hours.

Other interesting news:

▪ Football player in control

▪ Laughing depends on the genes

▪ Android named the most dangerous mobile operating system

▪ Good time to fly to Mars

▪ Human powered bioelectronics

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ Telephony site section. Article selection

▪ article by Quintus Curtius Rufus. Famous aphorisms

▪ article Why are sunsets crimson? Detailed answer

▪ article Desktop milling machine. home workshop