Theoretical prerequisites and initial experiments

The beginning of the radio history is associated with research in the field of electromagnetic radiation, conducted by scientists such as Michael Faraday and James Clerk Maxwell, in the middle of the 19th century. However, the key figures who made the main contribution to the emergence of radio are Guglielmo Marconi and Nikola Tesla.

In 1891, Nikola Tesla demonstrated the wireless transmission of energy using a Tesla coil. This became a defining event in the formation of radiocommunication, however, Tesla himself did not create a holistic radio system.

Guglielmo Marconi’s contribution

Guglielmo Marconi, an Italian scientist and inventor, is often called “the father of radio.” In 1895, Marconi developed a system that could transmit wireless signals over considerable distances. Marconi improved and advanced radio technology, creating radio stations and transmitters in different parts of the world.

In 1899, Marconi made the first wireless communication across the English Channel in world history, and in 1901 he demonstrated the reality of transatlantic radiocommunication.

Advancement of Broadcast

Communication In the early 20th century, the initiation of radio broadcasting set the stage for a revolution in global communication. In 1906, Reginald Fessenden’s landmark transmission of the first audible message featuring music and speech using amplitude modulation (AM) set a significant precedent in the journey of radio towards a mainstream communication medium.

By the 1920s, the radio had found its way into countless households worldwide. The United States led the charge in this global penetration with KDKA station in Pittsburgh, Pennsylvania, launching the first commercial radio station to commence regular broadcasts in 1920.

Nowadays, radio communication stretches far beyond traditional AM/FM signals, encompassing online radio stations, podcasts, and streaming platforms. The medium continues to evolve, mirroring technological advancements and shifting audience tastes, maintaining its role as a vital communication tool for millions across the globe.

Podcasts and Streaming: A New Era The rise of podcasts and streaming platforms can be attributed to their wide-ranging subject matter and the ease of content creation. Podcasts, a contemporary reincarnation of the classic radio show, offer audiences the flexibility to access programming on diverse topics as per their convenience.

Streaming companies like Spotify and Apple Music democratize radio by providing access to a vast collection of songs and podcasts anytime, anywhere. This freedom of choice hands listeners the power to control their content consumption.

20th Century Radio Revolution

The 1930s saw radio receivers becoming a standard household item across the US and Europe. This was radio’s golden era as it brought a revolution in news broadcasting, introduced innovative entertainment formats like radio shows and serials, and morphed into a potent instrument for political propaganda, notably during World War II.

The invention of frequency modulated (FM) signals in 1933 by American scientist Edwin Howard Armstrong was another significant step in the evolution of radio. FM offered superior sound quality compared to AM, making it the preferred choice for music broadcasts.

The Digital Radio Shift

The late 20th century heralded the transition to digital radio broadcasting, offering enhanced sound quality, expanded radio station offerings, and more informative broadcasts with details like track titles and artists.

Europe witnessed the introduction of the first digital radio systems like DAB (Digital Audio Broadcasting) in the 1990s. In contrast, the United States adopted HD Radio as its primary digital broadcasting format in 2002.

The Advent of Satellite and Internet

Radio As the 20th century drew to a close, the realm of radio expanded further, with satellite radio services like Sirius XM launching in the US in the early 2000s. These services offered hundreds of ad-free, genre-specific stations.

Internet radio extended broadcasting’s geographical reach, enabling anyone with an internet connection to establish their radio station. Modern platforms like Spotify, Apple Music, and Pandora deliver radio streaming services to mobile devices, reaching millions of listeners globally. The evolution of radio persists in response to technological advancements and societal shifts. Even today, radio remains a pivotal societal component, delivering news, entertainment, and crucial links in emergencies. Despite the advent of various new media forms, radio continues to hold its ground, reaffirming the significance of wireless communication in our world.

The post Radio – history of origin and development appeared first on SigHF.

The hidden aspects of the gaming atmosphere

In the context of online casinos, the discussion about music is not limited to background melodies, but also includes sound effects that accompany the player’s actions. They form a sense of reality and complement visual perception. Music and sound in online casinos deepen the player’s emotional response, increasing his involvement and satisfaction from the game process. New online casinos are becoming more and more popular nowadays and we recommend that you try playing at the best new online casinos in Brazil.

Music as a tool of psychological influence

Music in online casinos functions not only as an element of atmosphere creation but also as a means of psychological influence. It can stimulate the game, attracting players and maintaining their interest. Energetic melodies and rhythms can inspire players to take more risks, while more peaceful and relaxing compositions contribute to reducing stress and fatigue levels.

Sound effects as indicators of victory

Another key role of sound design in online casinos is success indication. Sound effects that accompany a win amplify positive emotions and encourage continued play. This contributes to increasing the duration of the gaming session and the likelihood of the player returning to the casino.

Thematic music accompaniments

Music in online casinos is usually selected in line with the game’s theme. This creates a unique atmosphere and helps the player immerse in the world of the game. For example, in a Western-style game, you could hear country music, while in a game with a maritime theme, the sounds of waves and seabirds would resonate.

Use of music in marketing strategies

Musical design not only improves the player’s interaction with the game but also serves as a powerful marketing tool. Quality music and sound effects can become a distinguishing feature of an online casino, which sets it apart from competitors. Moreover, a well-chosen soundtrack can evoke associations in the player that remain in his memory even after the end of the game, bringing him back to the service again and again.

Psychoacoustic effects

Psychoacoustics is an area of science that studies sound perception. In the context of online casinos, psychoacoustic effects can be used to enhance the sensation of excitement and thrill. For example, the use of high-frequency sounds can create a sense of time acceleration, prompting players to play more actively. Additionally, sound signals can create a “near-win” effect, which increases the player’s motivation to continue the game.

Music as a mechanism for creating communicative interaction

The musical and sound design in online casinos can become a topic for discussion in social media and forums, attracting attention and maintaining interest in gaming services. Gamers can debate about their preferences in music tracks and sound effects, exchange views and impressions, leading to the formation of communities around the casino.

Personalized approach to musical accompaniment

In the era of technologies that provide increasingly accurate methods for customizing the user experience, individualization of music accompaniment becomes increasingly important. Some online casinos already offer the possibility to adapt the music accompaniment according to the player’s preferences, allowing him to create his own unique sound space.

Breakthroughs in sound design

Modern technologies and innovations in sound design open new possibilities for music accompaniment in online casinos. The use of 3D sound or binaural recordings can significantly increase the level of immersion in the game, creating the illusion of actual presence in the casino. Technologies such as artificial intelligence and machine learning can also be used to create adaptive sound design that responds to the player’s actions and changes according to the progress of the game.

Sound accompaniment in mobile casinos

With the rise of mobile gaming, sound accompaniment becomes an increasingly important component of this format. Even on the small screen of a smartphone, the right soundtrack can create the atmosphere of a real casino and improve the overall impression of the game. Online casinos are a complex and dynamic industry that continually evolves and adapts to changing demands and interests of players. Music accompaniment plays a vital role in creating a unique gaming experience, ensuring participation and retention of players. With its ability to motivate, calm, and inspire, music remains one of the most potent tools that online casinos use to create an exciting and engaging atmosphere.

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Plan and prepare ahead of time

A key aspect of successful amateur radio contests is to plan and prepare in advance. Study the rules and requirements of the contest and determine your participation goals and strategy. Prepare your equipment, make sure it’s working and set up. Think about working plan with frequencies and bands.

Optimize time and manage resources

In amateur radio contests, time is of the essence. Plan your time and manage it efficiently. Allocate enough time for each band activity and set up your equipment in advance. Use various tools such as logs and logs to keep track of your contacts and manage your resources.

Be flexible and adapt

Successful amateur radio operators know how to be flexible and adapt to changing conditions. Learn the current propagation conditions and choose the most effective bands and frequencies to operate on. Be prepared to change your strategy depending on what’s happening on the airwaves. Stay alert to changes and respond quickly to opportunities.

Maintain good communication skills

Communication plays an important role in amateur radio contests. Refresh your transmission and reception skills. Be clear and concise in your messages. Consider the characteristics of different types of modulation, such as SSB, AM, and FM, and choose the most appropriate one for the contest.

Learn and learn from experience

Amateur radio contests are a great opportunity for self-education and development. Study and analyze your results after each contest. Identify your strengths, weaknesses, and areas where you can improve. Network with other amateur radio operators and learn about their strategies and best practices.

Successful amateur radio contests require careful preparation, optimization of time and resources, and flexibility and communication skills. By following these secrets and best practices, you can increase your chances of success and improve your amateur radio skills.

The post Secrets of Successful Amateur Radio Contests: Strategies and Best Practices appeared first on SigHF.

What is digital modulation?

Digital modulation is the process of converting information into a digital form for transmission over a radio channel. Instead of using analog signals, digital modulation presents data as binary numbers (bits) that are encoded and transmitted using various modulation schemes such as PSK (Phase Shift Keying), RTTY (Radio Teletype) and FT8 (Fast Fourier Transform 8).

Benefits of Digital Amateur Radio

Digital radio amateurism has a number of advantages over traditional analog radio amateurism:

Efficient use of the radio spectrum: Digital modulations allow you to transmit more information in a given bandwidth, which makes use of the radio spectrum more efficient.

Improved transmission quality: Digital modulations provide better immunity to interference and noise, resulting in a clearer, higher quality signal.

Advanced signal processing capabilities: Digital Amateur Radio allows you to use a variety of signal processing algorithms, such as coding/decoding, data compression, and error correction.

How to get started in digital amateur radio

To get started in the world of digital amateur radio, you’ll need the following:

Radio: Choose a radio station that supports digital modulation. There are special radios that are designed to work with digital signals, as well as some traditional radios that can be modified to work in digital mode.

Computer or other device: You will need a computer or other device that supports the appropriate software to process digital signals and communicate with the radio.

Software and Drivers: Install the necessary software and drivers that allow you to operate the radio station and process digital signals. There are various programs and packages, such as Ham Radio Deluxe, fldigi, and WSJT-X, which provide a wide range of options for working with digital modulation.

Study and Practice: Learn the basics of digital modulation and how the software works. Try transmitting and receiving digital signals, experiment, and join digital amateur radio networks.

Digital Amateur Radio offers exciting opportunities to expand your radio communications and delve into the technical aspects of amateur radio. Start by learning the basics, experiment, and enjoy the new possibilities that digital radio amateurism has to offer.

The post Introduction to Digital Amateur Radio: What It Is and How to Get Started appeared first on SigHF.

Semiconductors

Some crystals, such as silicon, germanium and others, are dielectrics. But they have a peculiarity – if some additives are added, they become conductors with special properties.

Some additives (donors) produce free electrons, while others (acceptors) create holes.

If, for example, silicon is doped with phosphorus (donor), we get a semiconductor with an excess of electrons (n-Si structure). If boron (acceptor) is added, the doped silicon will become a semiconductor with hole conductivity (p-Si), that is, positively charged ions will dominate its structure.

One-way conductivity

We conduct a mental experiment: we connect two different types of semiconductors to a power source and give energy to our structure. Something unexpected happens. If we connect a negative wire to an n-type crystal, the circuit closes. However, when we reverse the polarity, there will be no electricity in the circuit. Why does this happen?

By connecting crystals with different conductivity types, a region with a pn junction is formed between them. Some of the electrons (charge carriers) from the n-type crystal will flow into the crystal with hole conductivity and recombine the holes in the contact area.

As a result, uncompensated charges arise: in the n-type region from negative ions and in the p-type region from positive ions. The potential difference reaches values from 0.3 to 0.6 V.

The relationship between voltage and impurity concentration can be expressed by the formula:

φ = VT * ln (Nn * Np) / n2i, where

VT is the value of the thermodynamic voltage, Nn and Np are the concentration of electrons and holes, respectively, and ni is the intrinsic concentration.

When the plus is connected to the p-conductor and the minus to the n-type semiconductor, the electric charges will overcome the barrier because their motion will be directed against the electric field inside the pn junction. In this case the junction is open. But if the poles are reversed, the junction will close. Hence the conclusion: the pn junction forms a one-way conductivity. This property is used in the design of diodes.

From diode to transistor

Let’s complicate the experiment. Let’s add another layer between two semiconductors with the same structure. For example, we insert a conductive layer (n-Si) between p-type silicon wafers. It is not difficult to guess what will happen in the contact zones. By analogy with the process described above, areas with pn transitions are formed, which will block the movement of electric charges between emitter and collector, regardless of the polarity of the current.

The most interesting thing happens when we slightly stretch the layer (base). In our case we supply a current with a negative sign. As in the case of the diode, an emitter-base circuit is formed through which the current will flow. This will start to saturate the layer with holes, which will lead to hole conduction between the emitter and collector.

We have a visual model of a bipolar pnp transistor.

When the base is de-energized the transistor returns to its original state very quickly and the collector junction closes.

The device can also operate in gain mode

The collector current is directly proportional to the base current: Ik = ß * IB, where ß is the current gain, IB is the base current.

If you change the value of the control current, the intensity of hole formation on the base will change, resulting in a proportional change in the amplitude of the output voltage while maintaining the frequency of the signal. This principle is used to amplify signals.

By feeding weak pulses to the base, we get the same amplification frequency at the output, but with a much higher amplitude (set by the magnitude of the voltage applied to the collector-emitter circuit).

NPN transistors work similarly. Only the polarity of the voltages changes. Devices with the npn structure have direct conduction. Reverse conduction are pnp type transistors.

It remains to add that the semiconductor crystal reacts similarly to the ultraviolet spectrum of light. By turning the photon flux on and off or adjusting its intensity, you can check the operation of a triode or change the resistance of a semiconductor resistor.

The post How Does a Bipolar Transistor Work? appeared first on SigHF.

Unfortunately, the article doesn’t say a word about the fact that in civilian radio communications (whether CB, LPD or PMR), and by the way, in professional radio communications too, the main thing is not the range, but the intelligibility and stability, because these types of communications are utilitarian. In contrast to the amateur radio, where DX-QSO with, say, one of the islands of Polynesia “from the third run” barely over the noise of the air – it is an unequivocal success.

Only in passing we will touch on the fact that single-band (SSB) radios have many times more significant cost. Because formation of this type of modulation requires more complicated technical solutions, first of all related to the requirement of a very stable frequency retention in all operating modes, ranging from sudden temperature changes during a communication session (left the house in the frost) and ending with power “drawdowns” during the transition from reception to transmission. If the frequency shifts by just a few tens of hertz, you will hear a “robot-like” voice of your interlocutor. That’s why all single-band radios have a “fine” frequency tuning device.

However, this is the end of the “disadvantages” of SSB radios. But they have a lot of advantages. Despite the fact that SSB modulation is amplitude modulation, so it “catches” all noise of amplitude nature, compared to “classic” amplitude modulation (AM), these noise on the receiving end will have half the power, because one SSB band is twice as small as the double band of classic AM: that is, half the noise is cut off. It’s not hard to guess that because there is one band instead of two, the sensitivity of the single-band receiver, limited by the internal noise of its first stage, will also be twice as high. And in the transmit mode, compared to the same AM, a single-band transmitter of the same power is almost four times better: twice as much due to the fact that the signal again occupies only one band of two, and about twice as much due to the fact that half of the AM transmitter power goes to the “useless” carrier frequency modulated by the audio signal. Total total by total power of radio channel SSB in theory wins from AM 2x2x2x2=16 times! This can be disposed of in different ways: either to “shoot” further, or – on the same amount, but with cardinally reduced transmitter power, many times increasing the operating time of the radio on the same set of batteries, if it is portable. Another option is to get the transmission range as on AM (but with less interference), using full transmitter power and a couple or three times shorter antennas (provided that there is something to match them with your radio).

That’s the arithmetic

However, the multiple (in practice – still much lower than 16) benefit of the SSB over AM is possible only on the VHF and “upper” SW bands (including CB) away from cities and industrial sites, near which the industrial noise is ten times greater than the internal noise of electronic components and noise of “pure” ether, completely nullifying our energy advantage.

To the disadvantage of amplitude modulation we should add another thing: if two AM radio stations, having receivers with insufficiently steep dip of the audio frequency filter at its upper boundary, “stand up” on the band with the difference of carrier frequencies about 6 kHz (that is the edges of their spectra “against each other”), besides speech you will hear the constant whistling with this very frequency: a natural “nail in the head”.

Now I understand why AM has disappeared from the amateur bands?

But then why is it still in common use by “civilian” radio operators?

More precisely, in the CB environment, because LPD and PMR are governed by narrowband frequency modulation (FM).

It’s one of the “historical atavism” caused exclusively by the tradition of using AM by the truckers, they don’t need long distances: it’s hundreds of meters to kilometers in “their” caravan; to talk for a couple of minutes with an “encounter” when both cars are going a hundred kilometers per hour to the vanishing point – 5 km maximum; to warn the caravan behind at two hundred meters about a radar or a dangerous hole in the road – 3. …4 kilometers is enough.

And because the CB is cutting into “tight” grids with the step of 10 kHz, the situation with the “whistling” of extraneous carrier frequency and “splinters” of voice signal on AM is possible only if some radios work in the standard Euro grid, and the other – in so called “Russian” (it’s also “Polish”) shifted from the European by 5 kHz.

Further, it should be said that away from the cities with the accompanying strong interference background on the CB, with AM you can conduct longer connections than with FM, which sometimes saves in all kinds of critical situations. But only if you turn off the squelch at all and try to understand unhurried speech through the constant noise of the air. Uncomfortable, but effective. And since the useful signal barely exceeds the noise power, narrowband FM becomes inapplicable in this situation: it requires quite a significant threshold of noise excess by the useful signal, having approximately the same energy as AM.

But in the radius up to this threshold, FM has an indisputable and dramatically higher quality of voice signal relative to AM, as it is virtually immune to interference of amplitude nature and is clearly preferable in cities. I suspect that the “emergency” CB channels of the standard Euroset C, 9th and 19th, are “tied” to FM precisely because of the named “resistance” to amplitude interference. Another advantage of FM is the undemanding linearity of the transmitter, since this type of modulation emits a constant signal amplitude. It is desirable to have only a good bandpass filter between the antenna and the transmitter so that in case of overload on the input of the latter, to reliably damp out the “cut” by it out of band harmonic components.

In conclusion I will mention a nuance, characteristic for absolutely all types of modulation with speech signal (including many newfangled digital), not knowing about which many are trying to argue about the quality of signal and range of radio channel, transferring all “bumps” exclusively on the type of modulation with approximately equal parameters of receivers and transmitters of different radios.

We will talk about audio signal compression and the notion of peak factor, which is inseparable from it. Let’s start from the end: the peak factor is the ratio of the maximum signal to some average signal. The smaller the ratio, the more useful power the transmitter will emit. But the trick is that the “natural” peak factor at the output of, say, a dynamic microphone (which, unlike the amplifier following it, can hardly be overloaded) reaches ten or more. What to do? This is where compression is used, i.e. non-linear amplification of the signal: when it exceeds a certain threshold, a tenfold increase of the signal turns into, say, a threefold one and a twentyfold one into a fivefold one. This eliminates the overload of the modulation amplifier and increases the peak factor. But. with all that, the high-frequency component of the speech spectrum decreases significantly on “strong” signals, which leads to a decrease in its intelligibility (muttering). Therefore, the quality of the transmitted signal in balance with its power (optimal peak factor) is in no small measure determined by the formation of also balanced with a compressor amplitude-frequency response (AFC) of the microphone amplifier. About all this do not care much in simple and therefore cheap radios, which have some “gray” parameters, allowing more to guess what your interlocutor said, rather than hear it with full clarity and at much greater distances.

The post Civilian Radio: SSB, AM, FM and Microphone Amplifier Quality appeared first on SigHF.

What is a “Radio” or “Station”?

A walkie-talkie is a radio transmitting device. It consists of a receiver, transmitter, battery and antenna. A radio is used to transmit voice from one person to another over a distance. You do not pay a penny for it when you talk between radio stations. Therefore, at work, on a trip to hunting, fishing, picnic, ski resort, and just at the cottage or in the woods, put their phones in bags and talk on the radio for free.

What kind of walkie talkies to buy?

There is no perfect walkie talkie for all occasions. For optimum choice you need to know and take into account many parameters, such as: the anticipated conditions of use, what you need radios for, the frequency of operation, the frequency range and the power of the radio.

Operating conditions

When selecting radios, it is necessary to determine in what conditions they will be mainly used. For work in urban conditions more suitable frequency range UHF (400 to 520 MHz), to work in rough terrain, the forest, on the water or in the mountains more suitable frequencies LB band (25 to 50 MHz) or VHF range (136 to 174 MHz). If you plan to work in different conditions and in the city and on rough terrain, a large range of radios is produced:

• dual-band handhelds:
  Yaesu VX-3R, Yaesu FT-60R, Yaesu VX-8GR, Kenwood TH-F7E, Icom IC-E7(P7), Wouxun KG-UVD1P, Vector, Joker TH-UVF1, etc.
• Tri-band handhelds:
  Yaesu VX-6R, Yaesu VX-7R, Yaesu VX-8R, Yaesu VX-8DR, etc.
• multi-band automotive:
  Kenwood TM-V71E, Kenwood TM-D710A,E,K. Icom IC-706Mk2G, Icom IC-7000, Yaesu FT-7900R, Yaesu FTM-10SR, Yaesu FT-8800R, Yaesu FT-8900R, Yaesu FT-817ND, Yaesu FTM-350R, Yaesu FT-857D, Yaesu FT-897D, etc.

What you need the radio for

The design of the radio depends on this. If the radio is taken for various tasks, more suitable amateur radio stations, allowing you to change the radio settings manually. For professional tasks, such as construction or installation work, for security activities, professional radio stations are suitable. If the radio is to be used in conditions of high humidity and dust pollution, it must meet at least IP54, but if you want protection from moisture in the case of careless falling into water, the radio must comply with the standard not less than IPX7.

The main frequency bands used in radio communication

Shortwave (SW, frequencies 1.8-30 MHz), CB (Citizen Band, frequency 27 MHz), LB (Low Band, frequency 30-54 MHz), VHF (frequency 136-174 MHz) and UHF (frequency 400-470 MHz).

• SW band

It extends from 160 to 10 meters (frequencies from 1.8 to 30 MHz). This range allows radio communications over enormous distances due to reflection from layers of the atmosphere. Short waves are used for radio broadcasting as well as for amateur and professional radio communications. The quality of reception depends on various processes in the ionosphere, related to the level of solar activity, time of year and time of day. So in the daytime better propagate shorter wavelengths (25 and 31 meters), and at night – longer (41 and 49 meters). If the radio waves pass well, it is possible to contact Argentina from America without any problems. Radios operating on these frequencies are designed for marine applications (HF/HF), for radio amateurs, as well as professional work where long distance communication is important.

• CB band – 27 MHz.

With these frequencies produced radios for long distance drivers, for TAXI as well as a wide range of car enthusiasts. Radio 27 MHz range are poorly friends with electromagnetic interference, so their use is justified in nature – especially in dense forests and in conditions of very rugged terrain. Acceptable types of modulation are amplitude AM, frequency FM, single-band SSB. Besides, the 27 MHz band is an emergency channel (reporting and receiving messages about traffic jams, accidents, etc.) as well as an emergency service.

• LB band – frequencies from 30 to 50 MHz.

Signals in the Low Band are most susceptible to the influence of industrial interference, interference from household appliances, broadcast and television transmitters. The use of equipment of this range is optimal in rural areas, where the level of interference is much lower than in dense urban areas. The range is characterized by a good envelope irregularity of the landscape and the spread beyond the line of sight. The range for civilian communications is not authorized, and requires obtaining frequencies for work, or renting frequencies.

• VHF band – frequencies from 136 to 174 MHz.

One of the most versatile bands. Despite the fact that the radio stations in this range works well in the countryside and in urban areas, still the main use is justified in rough terrain, both in the flat landscape and in the hilly, as well as on the water. In the conditions of dense urban development quality of communication is significantly reduced. In the case of stationary operation of the radio plays a very important role the height of installation of the antenna, to increase the range of radio communication requires a much greater height of installation of the base antenna. Also these frequencies are used for maritime communications; they operate at 156.025 -157.425 MHz for transmitting and 156.050 – 163.275 MHz for receiving. According to the decision of SCRF from 01.06.99 3338-OR, frequencies in the band of 144-146 MHz are allocated for radio amateurs on a secondary basis. Recently, more and more radio amateurs devote their leisure time to a fascinating activity – amateur radio communication on VHF. The variety of processes occurring in the atmosphere and ionosphere of the Earth allows radio amateurs to conduct the most interesting radio communications. Along with distant tropospheric propagation of VHF amateurs use VHF reflection from sporadic ionized EM layer, from northern lights, from meteor trails. Radio communication using reflection of radio waves from the moon is of great interest.

• UHF range – frequencies from 400 to 520 MHz.

UHF range is considered an urban range and shows its best qualities in dense urban areas. The choice of this range is optimal when it is necessary to obtain a stable connection over short distances, for example, within the city and even when using portable radios provided a stable connection. For open terrain frequencies are not very convenient, as the radio waves of this range poorly envelope the irregularities of the terrain and have a strong attenuation in the wooded area. In the case of stationary operation of the radio station to get a long communication range will require a very high installation of base antennas. In accordance with the decision of the SCRF from 01.06.99 N3338-OR for radio amateurs frequencies of LPD and PMR are allocated on a secondary basis.

Radio stations operating on special frequencies are also operated, such as:

• Aviation band – 108-136 MHz frequencies.
• Naval range – frequencies 156.025 – 163.275 MHz.
  Ship-to-ship, ship-to-shore, NOAA weather channels and service channels are available on these frequencies.
• River band – frequencies 300-350 MHz.

Radio power

As for the output power of the radio – increasing the transmitter power is justified only when using the radio in a difficult electromagnetic environment. The best amplifier is an effective and well-tuned antenna, high selectivity and sensitivity of the receiver.

The post The Eternal Question of How and Which Radio Station to Choose! appeared first on SigHF.

Immediately a warning. If you want to build a cheap radio not for study or experimentation, you are in the wrong place. Immediately buy this LPD or a couple of these radios, for further you will not be interested.

When assembling the radio, you must have experience in soldering components, skills in determining the ratings of components and their installation on circuit boards by soldering. The tools for work are a low-power soldering iron with solder and rosin, wire cutters and a Phillips screwdriver.

The basis of the construction set is a set of JC986A radio parts which includes all needed components (except for the 9V battery) to assemble one radio in the range of radio telephones (frequencies around 49.8MHz). In total it is necessary to assemble at least two radios. All parts of the construction set are shown on the photo. The body is well made, but not of shockproof polystyrene. All of the plastic parts fell into place without any problems. The board withstood all soldering and troubleshooting and the tracks did not flake off. All tracks are covered with flux, soldering was performed without problems. The parts were complete.

Schematic of a simple radio

The radio is controlled by two switches. A floating switch S1 switches the transmit/receive mode of the radio (in the schematic the switch is in the receive mode). Switch S2 supplies power to the radio station. Transistor Q1 operates to receive in the superregenerative receiver circuit. The RF signal to the receiver is fed from the antenna Ant and the coil L1 to the circuit C1T1C4. The reception frequency is mainly determined by this circuit. The resonance frequency of the circuit can be changed with a tuning core. When switching switch S1 to transmit mode the receiver circuit goes to the mode of RF oscillator at the receiving frequency. Transistors Q2-Q5 are used to build a transformerless LF amplifier. In the LF reception mode the receiver signal through the chain R5, C10, C14 goes to the LF input and is amplified. The load of the VLF is the speaker SP. In the transmit mode the speaker is connected by the switch S1 to the capacitor C14 (it becomes a microphone) and the VLF amplifies the signal from the speaker. The load of the LPF is the high-frequency generator which is supplied with alternating voltage from the middle point of the LPF amplifier through the limiting resistor R9. The AC voltage modulates the RF output signal into the antenna. The antenna is connected through an extension coil – choke L1. On the board there are places for three more elements of the tone call when transmitting – R10, C7 and the button (these parts are not included in the kit).

Step-by-step instructions for assembling the radio station with your own hands

Step 1. When you receive the parcel, check the completeness of parts of the case and radio components. Study the markings. Resistor ratings are color-coded. A key to read is included on the page. Do not confuse the L1 choke with the resistors, it is much larger. Smaller parts are best kept in a closed box. Examine the circuit board from the parts side to understand where to mount the parts.

Step 2: Start the soldering process by installing the resistors. Form the electrodes of the resistor. Solder it to the board and cut off the protruding electrodes with wire cutters. This is how we install all the elements with long electrodes. The position of each element is marked on the board. Be careful not to make mistakes. Solder all the resistors one after the other.

Step 3: Solder the extension coil L1.

Step 4: Solder the capacitors.

Step 5. solder the electrolytic capacitors. The elements have the polarity of the installation.

Step 6. solder the circuit coil T1, switch S1. Make sure to solder the metal body of the switch to the board.

Step 7. solder the transistors by strictly following the markings on the board.

Step 8. With the cut off electrodes we solder jumper J1 to the board.

Step 9: Check the correctness and quality of elements installation. You can rinse the board from the flux residue with alcohol. Install the plastic button for switching between transmit and receive. Fix the board to the housing with two self tapping screws.

Step 10. Install antenna. On top of the antenna we put the plastic cap. Solder the connection wire to the board to the lobe of the antenna. Pieces of wire from the parts solder the switch S2. Check the operation of the power switch. The switch lever should move when you rotate the plastic knob.

Step 11: Re-solder the solder wires to the battery compartment terminals. Install the terminals in the battery compartment. Solder the speaker connection wires and the power supply wires from the battery compartment. Observe the polarity! You can insert the battery and, if you are sure that everything is assembled correctly, apply power. You should hear the hiss of the receiver working from the speaker. You can check the operation of the transmitter with the field indicator. Connect the two halves of the case with 5 tapping screws.

Step 10. Assemble the second radio station in the same way. For proper operation, the receiving and transmitting frequencies of each radio must be identical. To do this, the board of one radio station is removed from its fasteners. An improvised dielectric screwdriver with a straight slot is made from a match. We turn on one radio station to receive, the second disassembled one to transmit (the distance between the stations is 1 meter) and by turning the core of the circuit with a wooden screwdriver we achieve a loud sound of the voice on the reception of the first radio station.

Repeat these operations at distances of 5 and 20 meters. It is better to tune up in the open air. Do not forget, radio stations are simple and the signal will be influenced directly close to the antenna objects and signal capture by the receiver may not work. It is very useful to use SDR USB receiver. Watch this video. It will allow you to estimate the signal strength, frequency, frequency stability and quality of modulation. Assemble the case of the second radio station.

This completes the configuration of the radios in this circuit solution. The communication range between the radios in the open area is about 100 meters. But this is not the limit, with appropriate modification or simply by connecting appropriate antennas communication range can easily be several kilometers. If interested in the topic, the author will publish some of the improvements. The station is interesting for its range and amplitude modulation. Interference in your conversations is possible, but unlikely. The radiated power in the radio antenna is less than the limits that require a permit or registration.

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