Menu English Ukrainian russian Home

Free technical library for hobbyists and professionals Free technical library

Free library / Schemes of radio-electronic and electrical devices

Scanning mode in radio station ALAN-100+. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Civil radio communications

Comments on the article Comments on the article

The radio station "ALAN-100+" and similar ones are among the most accessible and widely used. Unfortunately, they have a limited set of service options. For example, these stations do not have an automatic scan mode that stops on a channel where a signal is present. They are not designed to work in the Russian standard. To introduce it, in addition to changes in the radio station, it will be necessary to refine the front panel to install additional switches. If this is undesirable, you should use the already existing switch designed to turn on the 9th channel.

The proposed revision can also be carried out in those radio stations in which the changes described by the author in the article "Refining CBS radio stations" ("Radio", 1996, No. 12, p. XIV -XV) have already been made.

Scanning mode in radio station ALAN-100+
(click to enlarge)

Schematic diagram of the scanning node is shown in the figure. The device contains an RS-trigger on the elements DD1.1 and DD1.2, a multivibrator on the elements DD2.1 and DD2.2, electronic keys on the elements DD3.1 - DD3.4. In the upper position of the switch SA1 according to the scheme (mode "5", European standard), a high level is supplied to the input 1 of the DD1.1 element, and at the input 6 of the DD1.2 at this time it is low. In this case, the output of the element DD1.1 will be a low level, which will go to the control inputs of the keys DD3.1 and DD3.2. They will be in a high transient state, so relay K1 is de-energized, capacitor C4 is open, and the radio is in mode "5". A high level from the output of the element DD1.2 opens the transistor VT2 and the HL2 LED is on.

In the lower position of switch SA1 according to the diagram, the output of element DD1.1 will be high, the keys DD3.1 and DD3.2 will go into a conductive state and relay K1 will work. With its contacts, it will connect an additional capacitor C4 to the reference oscillator of the radio station. The frequency of the oscillations generated by the generator will decrease and the radio will go into "0" mode (Russian standard). The transistor VT1 will open and the HL1 LED will light up.

If the switch SA1 is set to the middle position, then the RS-flip-flop will remain in the previous state, i.e. the mode "0" or "5" will not change. But a high level will go to the inputs of the DD1.3 element, and a low level - at the output of this element - will allow the signal to pass through the DD1.4 element from the output of the comparator of the radio station's threshold squelch system (IC2 chip). If the output of the comparator is a low logic level, which means there is no signal in the channel, then the output of the DD1.4 element will be high (and the output of DD2.3 will be low) and the pulses from the multivibrator will begin to flow through the DD2.4 element to the control inputs of the keys DD3.3 and DD3.4. Thus, with an interval of 0.2 ... 0.4 s, the keys will close the "UP" button for a time of about 0.02 ... 0.04 s. This corresponds to a tuning time for all channels of about 8...15 s. If you move the SA1 switch to the middle position, the radio will enter the automatic cyclic scanning mode for all 40 channels. Depending on what position the switch was in before, scanning takes place in the "0" or "5" mode.

Automatic scanning occurs until a signal with a level exceeding a predetermined threshold appears in any channel. As soon as this happens, a high level will appear at the output of the radio comparator and the capacitor C2 will quickly charge through the diode VD1. A high level will appear at pin 13 of the DD1.4 element, and the passage of the multivibrator pulses to the control inputs of the keys DD3.3 and DD3.4 will be prohibited. Automatic scanning will stop and the radio will remain on the channel where the signal is detected, as long as the signal is present and even for 1...2 s after it disappears. This is done so that during transmission pauses the radio station would not immediately go into scanning mode. When the signal fails, capacitor C2 slowly discharges through resistor R4, which provides a delay. If the detected signal is of interest to the operator, it is necessary to move the switch to one of the extreme positions and the scanning will stop.

In the extreme positions of the switch SA1, the inputs of the element DD1.3 will be low. So the same will be at the output of the element DD2.4. The keys DD3.3 and DD3.4 in this case have a high resistance, therefore there is no automatic tuning. And so that when switching modes from "0" to "5" and vice versa, the scanning mode does not turn on, the R1C1 circuit is installed.

It should be noted that the described refinement does not disrupt the operation of the radio station in the manual tuning mode by channels. If there is no need for light indication of modes "0" or "5", then transistors VT1, VT2, resistors R7, R8 and LEDs HL1 and HL2 can be excluded.

Almost all parts of the device are mounted on a segment of a unified board. Resistor R1 and capacitor C1 are installed on the terminals of switch SA1 (on the board it is designated SW2). Relay K1 and capacitor C4 are located on the radio board, and LEDs, if necessary, on the front panel. The additional board itself can be attached above the main board at the location of the IC1 chip.

It is permissible to use parts in the device: microcircuits of the K564 series, transistors KT315, KT312, KT3102 with any letter indices, capacitor C2 - K50-6, K53, K52, the rest - KM. Diodes can be any small-sized pulse, relay K1 - RES49, RES60, REK37 with a response voltage of 7 ... 8 V.

A device assembled from serviceable parts does not require adjustment. By selecting capacitor C3, the most convenient scanning speed is set. As for the setting of the "0/5" modes and the installation of the relay, this was described in detail earlier (see "Radio", 1996, No. 12). It may happen that connecting the capacitor C4 to TC1, X1 will lead to a breakdown in generation. Then you need to use a larger capacitor C4 and connect it to another output of the quartz resonator X1.

The radio needs to be done a little refinement related to changing the functions of the switch on the front panel. This switch is double, but its sections are connected in parallel, so you must first disconnect them. To do this, carefully cut the printed conductors going to the switch. In this case, broken contacts between other elements will have to be restored with pieces of the mounting wire. Then the switch is soldered in accordance with the diagram and the device board is connected to the radio station.

Author: I. Nechaev, Kursk; Publication: N. Bolshakov,

See other articles Section Civil radio communications.

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

Census in the ocean 17.08.2010

More than 2000 biologists from different countries of the world cooperate in the international project "Census of the population of the seas".

The project lasted ten years and is nearing completion. More than 50 new forms of marine life have been discovered, including 000 species of marine worms, hundreds of small crustaceans and many microbes.

It is believed that a billion species of microbes live in the seas and oceans, and their total number is nonillion - this is one followed by 30 zeros. By weight, microbes can make up 90% of all biomass in the sea.

Other interesting news:

▪ The stadium generates electricity

▪ Ancient Roman concrete can be restored

▪ Electric car Hyundai IONIQ 6

▪ Sanyo Hacti HD1 compact camcorder

▪ Lighting from a balloon

News feed of science and technology, new electronics


Interesting materials of the Free Technical Library:

▪ section of the site Electrician's Handbook. Article selection

▪ article Study, study and study. Popular expression

▪ article Whose brain is the largest compared to the size of the body? Detailed answer

▪ article Working with a device for cutting metal products (cutting machine). Standard instruction on labor protection

▪ article Automatic TV switch. Encyclopedia of radio electronics and electrical engineering

▪ article Appearance of a huge bouquet of flowers. Focus Secret

Leave your comment on this article:


Email (optional):

A comment:

All languages ​​of this page

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