VHF converter. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / radio reception
Comments on the article
VHF FM broadcasting in the CIS countries is carried out in two bands: 65,9 ... 74,0 MHz-VHF1 and 100,0 ... 108,0 MHz-VHF2. However, radios usually only have one of these. The converter offered to the attention of readers allows you to receive stations of both ranges. It is connected to the antenna and a common wire - the "ground" of the radio receiver, and the radio receiver antenna also serves as the converter antenna. The converter turns on when the supply voltage is applied.
Schematic diagram of the converter is shown in the figure. It is a modernized version of the converter proposed by I. Aleksandrov in the article "VHF Converter" ("Radio", 1992, No. 8, p. 44). Modernization consists in replacing the frequency converter on a field-effect transistor with a diode mixer.
The load of the frequency converter of the VHF converter is the relatively low input impedance of the radio receiver Rin = 75 Ohm.
If the frequency converter is made on a field-effect transistor, as is done in the converter mentioned above, then its voltage transfer coefficient K will be equal to
Cp< 20lg(0.25KinSmaxRin)=-11dB,
where Kin = 5.0 is the transfer coefficient of the input circuit of the converter, Smax = 0,003 A / V is the maximum value of the steepness of the direct transmission characteristic of the KP303G field effect transistor at a frequency of 100 MHz, i.e. the sensitivity of the receiver when using the converter deteriorates by almost four times.
From the point of view of matching the output impedance of the frequency converter and the input impedance of the receiver, it is more advantageous to use a diode mixer, the transfer coefficient of which is -7...-9 dG> at a load of 75 Ohm, and the converter becomes simpler.
The oscillations of the local oscillator, made on the transistor VT1, with a frequency (fg) of about 34 MHz, are fed to the anode of the VD1 diode, and the radio station signal received by the receiver antenna is sent to its cathode. At the same time, there are also voltages of frequency conversion products: fc + fg or fc-fg, which are allocated respectively by receivers with VHF1 or VHF2 bands. Thus, any receiver can receive two-band radio stations.
About the design elements, features of manufacture and adjustment of the converter are described in the article by I. Aleksandrov. Any low-power high-frequency germanium diode can be used as a VD1 diode. A DM choke with an inductance of 1 μH was used as a coil L10. Coil L2 contains 2 + 8 turns of wire PEV-2 0,4, wound on a frame with a diameter of 5 mm, a length of 10 mm with a brass trimmer 6 mm long.
The disadvantage of the converter is that the input circuit of the receiver, together with the antenna, is not tuned to the frequency of the received station when the converter is operating, which somewhat reduces the sensitivity. This disadvantage is less pronounced in lower class radios with a non-tunable broadband input circuit. AT) a significant signal level at the reception point, this disadvantage pays off by the simplicity of the proposed design.
If several stations operate in each VHF band, then for the convenience of operating the converter, you can connect a 5 ... In this case, the dimensions of the converter are determined by the dimensions of the existing KPI.
If it is possible to switch the antenna when switching from range to range, then a diode ring mixer can be used in the converter, which allows using a tuned input circuit and has a transmission coefficient of -7 ... -8 dB at a load of 75 ohms.
Author: N. Turkin, St. Petersburg; 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 Dogs and primates see magnetic fields
02.03.2016
Some animals have the ability of magnetoreception, that is, they can notice magnetic fields. Now scientists have found that the molecules responsible for this trait are also found in the eyes of dogs and some primates, which means they too can see magnetic fields.
Cryptochromes are a common group of light-sensitive molecules that exist in bacteria, plants, and animals. In addition to regulating circadian rhythms, these specialized proteins allow some animals (birds, insects, fish, and reptiles) to sense magnetic fields, thus allowing them to sense direction, height, and location. Some mammals, such as bats and moles, also have this ability, but its distribution among other mammalian species is virtually unknown.
Now, in the first study of its kind, scientists at the Max Planck Institute and several other institutions have examined the presence of a version of this molecule called cryptochrome 1 in the retinas of 90 mammalian species. It turned out that canine carnivores like dogs, wolves, bears, foxes, and badgers have it, but cats don't. And among primates, orangutans, rhesus monkeys, crabeater monkeys, and others have cryptochrome 1. Details of the study can be found in Nature Scientific Reports.
Although magnetoreception is considered the "sixth sense", it is actually related to vision. Magnetic fields activate cryptochrome 1 in the retina, and animals "see" the slope of the magnetic field lines relative to the earth's surface. Active cryptochrome 1 is located in the light-sensitive outer segments of the mammalian "cones", and therefore the researchers believe that they are responsible for magnetic perception, and not for controlling circadian rhythms or some other visual capabilities.
It's not entirely clear how mammals like dogs and primates use magnetoreception, but foxes can help here. When they hunt, more successful attacks on mice are carried out by attacking from the northeast direction. In primates, a built-in compass can affect the orientation of the body in space, or it can be just an evolutionary atavism, now practically unused.
The next step for scientists will be to prove that animals are using cryptochrome 1 to its full potential, or that the molecule is performing some other task in the retina.
|
Other interesting news:
▪ Free Internet from Facebook
▪ Liquid Cooled TeamGroup M.2 SSD
▪ Asus ZenPower Max portable battery
▪ Smartphone Nokia N9
▪ New Class Drones Dragonfly Pictures
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ site section Voltage converters, rectifiers, inverters. Article selection
▪ Watergate article. Popular expression
▪ article How does a male emperor penguin help a female in breeding chicks? Detailed answer
▪ article Working on a machine for creasing covers and sticking ribbons on the cover. Standard instruction on labor protection
▪ article Automatic defrosting of the refrigerator. Encyclopedia of radio electronics and electrical engineering
▪ article Attachment for a soldering iron. 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
www.diagram.com.ua
2000-2024
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese