Selecting an SDR transceiver. SDR HAM - Introduction

There was a time when I was interested in radio communications on the HF range, 160 and 80m, but when I moved to the city, I put it all on the top shelf due to lack of time and space to deploy the antenna, although the 160-meter range was “extinct.” At one time, for 25 hryvnia, I received permission with the call sign UU5JPP.

But I still feel like going on the air, and then I started surfing the Internet looking for new transceiver circuits, and came across this circuit, which will be discussed, which the author of this circuit will talk about.

Somehow there was a desire to make an SDR transceiver. And the search for information and diagrams on SDR transceivers began. As it turned out, there are practically no completed transceivers, with the exception of various versions of the SDR-1000. But for many, this transceiver is both expensive and complicated. Various versions of the main boards, synthesizers, etc. were also published. ,those. separate functional units. Tasa YU1LM, which also made the complete “AVALA” transceiver, did a lot in the field of development and popularization of simple SDR technology, and we can recommend its designs for beginners in this field and those who want to try what SDR is at minimal cost.

In the end, I decided to make my own, as simple as possible and at the same time high-quality SDR transceiver. YU1LM materials and other publications were used during development. It was decided to make the mixer on a 74HC4051 - Sergei’s US5MSQ direct conversion receiver was once made, with a mixer on this chip. And the use of 74HC4051 in a transceiver allows you to make a very simple mixer - common for both the receiving and transmitting paths. The quality of work of this mixer is quite satisfactory.

The transceiver is built using a direct conversion scheme from an operating frequency to an audio frequency for signal processing by a computer sound card... Therefore, much that has been written about the direct conversion technique also applies to SDR. In particular, the need to suppress the non-working sideband (in the SDR mirror channel) using the phase method.

• Operating frequency range 14.140 – 14.230 MHz. (When using a quartz crystal at a frequency of 14.185 MHz and a sound card with a sampling frequency of 96 kHz)
• The sensitivity is about 1 µV and highly depends on the quality of the sound card.
• The dynamic range of intermodulation is more than 90 dB - there was nothing more precise to measure it with.
• Carrier suppression for transmission is more than 40 dB (I got 45 - 60 dB) and depends on the specific instance of the 74HC4051, as well as on the quality of the tuning.
• Suppression of the mirror channel is more than 60 dB with the correction program.
• Output power is about 5 W.

It is clear that an SDR transceiver requires a control program, and my choice fell on the M0KGK program because of the program’s ability to correct amplitude and phase throughout the entire operating range of the sound card and memorize calibration points. This is very important. This property of the program allows you to suppress the mirror channel very well. Due to the lack of ability to store calibrations at several sound card frequencies in the program, I refused to use it - this program works great with SDR transceivers with built-in frequency synthesizers, where the frequency tuning is done by the synthesizer, and not by the sound card frequency.

Click on the image to enlarge

The circuit diagram is simple and I will not describe the operating principle. You can read this from Tasa YU1LM, although in English. No errors were found in the printed circuit board. For ease of soldering, I signed the values ​​of the elements in the drawing of the printed circuit board, and not the serial numbers of the elements.

The transceiver practically does not need configuration, and with proper installation it starts working immediately. With the correct settings of the M0KGK program, of course.

It is clear that many will have difficulties purchasing a quartz resonator. Therefore, in case of its absence or because of the desire to have the entire 20 m range, you can simply use an external VFO or synthesizer at the operating frequency, the signal from which must be fed to the 1st pin of the 74HC04 through a 10 nF coupling capacitor. Do not install capacitors C63 and C64.

Working with this transceiver is very pleasant and convenient. All computer mouse control. The entire spectrum in the 96 kHz band is visible, and by simply indicating or “dragging” the program filter, we instantly tune to the station of interest. Very quickly and clearly. After working on this transceiver, working on a regular one is already missing something - visual information about the situation on the band.

Questions and myths about SDR

Questions and myths

One of the most common questions today after purchasing an SDR radio is: “Which computer should I use?” or “What computer should I buy that will last for several years?” The short answer is, today – anyone. And this article could end here. I had the opportunity to test the transceiver on several computers with different parameters, from which I decided to compile a small article about “What and how much” in percentage.

Today, if after purchasing a transceiver you decide to immediately update your computer, then by contacting the nearest computer store, you can assemble any system in the range from 10 to 30 thousand rubles. Any computer system unit assembled today will ensure the Power SDR program runs with minimal resource load. But not everyone should immediately run to the store for a new computer. You should only run for a new computer if you have a fairly old system unit - this is from 2007 and older. My opinion is that today’s computers, even not the most expensive ones, are better suited for SDR than the most expensive ones from 3-5 years ago. For example, if we take a 2-core processor with a frequency of 2 GHz manufactured in 2007 and the same frequency in 2011, then their computing power will differ significantly! This means that the Power SDR program will use many times more resources on the old processor. How much it is in numbers - you will see for yourself a minute later.

For experiments, I used several computers of different configurations and different years of manufacture, several laptops, and even decided to try a couple of netbooks as particularly weak, but quite possible options for use. Today, all computers sold can be divided into several categories:

1. A computer with a classic configuration, including a system unit with a motherboard and a full-fledged processor - the fastest system today. Price category 8 – 40 thousand rubles. depending on the type of processor, motherboard, amount of RAM, hard drive and video card;
2. Miniature system units, nettops and monoblocks based on ATOM processors, which are soldered to the motherboard. Price category from 10 to 25 thousand rubles;
3. Laptops based on full-fledged processors, price category from 15 to 50 tr;
4. Netbooks based on ATOM processors with prices from 8 to 15 thousand rubles.
5. Tablet computers with ATOM processors from 15 to 25 thousand rubles.

All of these categories of computers today will work with the Power SDR program. They will differ only in the percentage of system load. Thus, netbooks based on the ATOM processor will load the system from 30% and above. And computers based on full-fledged processors, up to a maximum of 30%, and then 20-30% will be on the lowest-speed processors. You should also know that processor speed is not the only indicator of computer performance that is responsible for all the mathematics in the Power SDR program. This parameter also depends on the amount of RAM. Today it should be at least 1GB. At this minimum, Power SDR will still work tolerably. And the weaker the processor, the more critical its quantity is for normal operation. You will see this below in the text. Those. It’s better not to skimp on the amount of memory, and if possible, equip the motherboard with as much memory as possible.

For those who are thinking about changing or changing a computer, and also, if changing, then to which one, I present the systems I tested:

1. System unit based on AMD Athlon 64 x2 Dual Core Processor 4800+ processor with a frequency of 2.5 GHz. RAM 4Gb – load 13…16%; ()
2. System unit based on an Intel Pentium 4/800MHz processor (bus) with a frequency of 2.6 GHz, RAM 1Gb – load 25...30%; ()
3. System unit based on Intel ATOM D410 processor, RAM 2Gb – load 34...40%; ()
4. System unit based on Intel ATOM D525 processor, RAM 4Gb – load 20...25%; ()
5. System unit based on VIA PV530 processor, RAM 2Gb – load 65...70%; ()
6. Sony laptop processor Intel Core 2 Duo T6400 2GHz, RAM 4Gb – load 14…16% ()
7. HP laptop processor Core 2 Duo T8400 2.24GHz, RAM 3Gb – load 18..22%; ()
8. Netbook Asus EEEPC 900, RAM 2Gb – load 40-45%; ()
9. Netbook Asus EEEPC 4G, RAM 1Gb in light mode 630MHz – load 80...85%; ()
10. Netbook Asus EEEPC 4G, RAM 1Gb in full speed mode 900MHz – load 55...60%; ()

Recent data using older netbooks such as EEEPC 900 and EEEPC 4G shows that Power SDR can work on such weak computers. Moreover, EEPS 4G worked on an external 19" monitor, and in 2 modes - 630 MHz and 900 MHz. In both modes, the program worked, but with different amounts of processor load. Today you can buy a netbook with a more powerful processor and more RAM. Use they can, for example, be used as a second receiver or transceiver for a summer residence in conjunction with the Flex SDR-1500 transceiver. The laptops and AMD computer were running Windows 7, all others were running Windows XP Sp3. The transceiver was using the SDR Flex-1500.

All presented loading figures have an average value - we see this in the screenshots. The UR5EQF log program was installed on each computer and the load increased by no more than 5-7%. Also, I would like to note that processor load practically does not depend on the quality of the video card used and the amount of memory on it. When testing the Power SDR program on system unit No. 2 with an Intel Pentium 4 processor, I tried installing a very old Riva TNT 2 video card with 16Mb of video memory and a powerful GeForce 6600 gaming video card with 512Mb of video memory. The processor load figure has remained virtually unchanged. This suggests that all calculations of the DSP block in the program rest on the shoulders of the processor used. And the difference in boot numbers on laptops shows that RAM is actively used in calculations. The processor in the HP laptop is more powerful and faster than the 250 MHz Sony laptop, but it has less memory. Accordingly, the difference in load was about 7-10% in favor of Sony. Based on the figures shown, we can assume that full-fledged processors of today - Intel i3, i5, i7 will give even lower load figures, because they are made using more modern technology and have much greater performance than older processors at the same frequencies.

Of particular interest is the combination of the SDR Flex-1500 with a tablet computer based on the Atom N570 processor. Unfortunately, I did not have the opportunity to test such an interesting combination due to the lack of a tablet for testing. If you have the opportunity, conduct a test and share your impressions... You should probably expect a processor load of around 20-40% and a very interesting way to control the Power SDR program with your fingers.

To collect statistics on the degree of computer load, I suggest that everyone who has such an opportunity take a screenshot of the desktop similar to the screenshots above and send it with a description of the computer to. As information accumulates, it will be posted on the website.

The main myth is that a computer is scary, difficult and problematic.

A computer is already an urgent need of the modern world, helping to solve many problems, incl. and amateur radio nature. From calculations on a modern engineering calculator to modeling circuits and antennas. In the field of shortwave radio amateurs, this is mainly control of the transceiver, maintaining a hardware log, generating reports after the competition, printing, receiving and sending electronic QSL cards, monitoring progress, informing about the appearance of a rare, distant station on the air, and finally, today, Complete signal processing, both for reception and transmission, using SDR technology. Modern software is already well-honed and software failures have become a rarity.

The second myth is that computer hardware is buggy and it is difficult to assemble a stable computer yourself.

The times when individual components of a system unit could conflict with each other have already sunk into oblivion about 10 years ago. The main players in the computer market have long agreed with each other on protocols and specifications. Large companies have long ago bought up small ones. The main elements of a computer are already contained to a greater extent on the motherboard, and there is even a class of motherboards where “all in one”, incl. and the processor is soldered. But if you are still afraid to assemble a computer yourself, then today stores offer a large selection of already assembled system units for every taste and any price category. Basically, they already have installed software and have been tested for stability. For those who are especially worried, we can recommend a laptop. These computers are tested at the manufacturer's factory. Those. we can say that today a good laptop is not only a mobile computer, but also one of the most stable.

The third and most common myth is that SDR is difficult to set up and operate.

SDR was complex at the very beginning of its appearance. The first implementation of an SDR transceiver in the form of the Flex SDR-1000, and then all the countless clones of this transceiver, required the use of a separate sound card, a whole bunch of cables and wires. There were a lot of problems associated with this. From setting up the sound card to calibrating the program. Problems with connectors, sound routing, driver and operating system compatibility. Now all this is in the past! The youngest model of the SDR transceiver SDR Flex -1500 already contains a modern and high-quality ADC and is controlled via a single USB cable. Also, ADCs are already built into the older Flex-3000 and Flex-5000 models. The setup program will install the necessary drivers and calibrate the software of the radio receiver and transmitter. The problem of mirror channel suppression across bands no longer exists. The SDR Flex-3000 and Flex-5000 transceivers (in the Flex-5000ATU package) contain an auto-tuner, and you do not need to re-tune the antennas if you have replaced the old transceiver with a new SDR transceiver. Now you can simply insert headphones and a microphone into the appropriate sockets and work on the air. And the main feature of the new Flex-radio transceivers is full support and compatibility of all released versions of software and hardware with all new versions of Microsoft's Windows operating systems.

Myths about earthing

In addition to questions related to choosing a computer for an SDR transceiver, there are also several myths about grounding. In my opinion, this is the most dangerous and most widespread myth. Story Not the use of grounding shows that history teaches no one. And every person who once suffered quite severely, then laments, “Why didn’t I ground myself?”, but it’s too late - everything burned down or he himself was injured. In the worst case, violation of the rules for operating electrical equipment leads to death. The most common option is damaged equipment. And it’s especially offensive when this equipment costs a lot of money. SDR class transceivers are more susceptible to failure due to violation of operating and grounding rules. This is due to the specific operation of power supplies. The consequences of improper RF grounding manifest themselves in the form of computer and transceiver freezes. In especially severe cases, this manifests itself as a “burning” of the computer case or transceiver.

Let's consider two types of grounding. The first is electrical grounding. The second is radio frequency grounding.

Electrical grounding- this is a wire through which constant electrical potential flows to the ground. Those. a conductor having 0 electrical resistance for direct current between a device at potential and ground. In a particular case, this is a wire for electric current with a frequency of 50 Hz.

How does this grounding work?

If, quite by accident, any element of the amplifier or transceiver that is under high voltage burns out (usually in the power supply), or the power cord simply falls off and the fuse does not blow, then the housing of the device, amplifier, power supply and/or transceiver will be under high voltage potential. If you touch it, you risk receiving an electric shock. In extreme cases, your fingers will be pinched, and in worst cases, they can kill you. A good example of a gross violation of screening safety rules. To remove high potential from the body, you need to provide it with a conductor that will have significantly less resistance than the human body. This is the ground wire.

Every computer case contains a switching power supply. The circuit design of all small-sized switching power supplies is such that on the computer case Always there is a potential equal to half the power supply of the electrical network between the computer power supply case and the ground or the 0th wire. Sometimes even in the off state (depending on the power supply). Those. 100 - 120 Volts are always present on the body. For some, this potential has repeatedly “bitten” their fingers. Now imagine the situation. We connect the transceiver to the computer. This transceiver is connected by a coaxial cable to an antenna, which on the roof or in the garden/field has good contact with the ground or is well grounded. In this case, an electrical potential of 100-120 Volts will be present between the transceiver and the computer. And the moment you connect the transceiver to the computer, you may notice a spark. Now imagine how the transceiver feels? If you are lucky and the common contacts of the connector devices are touched first, then the potential difference is removed from the case and the connection proceeds normally. And if the common contacts touch second, then this potential is directly applied to the elements of the communication port and as a result we have a “defective” transceiver or computer with a burnt-out port. Friends, is this not about you? Well, thank God! This is not about you yet. But for those who were unlucky, it is probably sad now to remember the dead transceiver or computer and the headaches associated with the repair and subsequent sale of the former dead one. Therefore, friends, be sure, before using an SDR transceiver with a computer, find any point with zero potential or grounding, for example, a cold water pipe for those who live in an apartment. Those living in a private house, do not be lazy and make a grounding loop, and only then, after grounding, use the transceiver and computer to your health.

Those who say that they do not use grounding in their lives, and those who recommend not to use it at all, are in the “risk group” for the time being. Run away from such advisors, because they themselves do not follow safety precautions, and they will also advise you to endanger your life and the life of your equipment.

This is especially true for users of SDR transceivers!

Radio grounding e - the wire through which the HF potential, not emitted by the antenna, “flows” to the ground.

Imagine that a hot colorless liquid runs along the antenna cable and evaporates at the antenna feed point. And the part that has not evaporated flows back through the cable into the transceiver, at the same time wetting the transceiver, the power wires and the computer. This is a liquid in a superfluid state. Moreover, it is also hot, flammable and also poisonous. Flowing into the microphone, it begins to squelch, and flowing into the amplifier, it begins to burn. In the computer, this liquid closes all contacts, and it begins to malfunction. Flowing through electrical wires, this liquid stinks and stings the eyes.

In most cases, correct RF grounding and RF shielding help solve all these problems. The first RF ground point should be on a properly constructed antenna. One of the main elements of the antenna is such a well-known construct as the “balun”. It allows you to compensate for the RF voltage on the cable at the antenna feed point with the cable and thereby minimizes the penetration of RF through the cable into the room where the transmitter is located. A sizing device can be compared to a basin into which excess liquid drains and is removed. Quite often the balancing device is neglected. But in vain. Technically, the balun is not an RF ground, but in the context of solving the problem, it plays a major role. A correctly executed antenna design has high-quality RF grounding through an electrically grounded mast or antenna mounting platform. Also, the main RF grounding is good antenna counterweights. This applies to a greater extent to vertical asymmetrical antennas. If their number is large enough (>4..8) and they are tuned into resonance, then the RF traveling along the cable will also be minimized. You can also get rid of RF energy interference and RF energy penetration through the cable using RF barriers or RF insulators. These include ferrite latches or ferrite rings, such as . It is enough to wind a few turns of cable around such rings, and for RF energy such a cable will have high resistance. This method of RF isolation effectively shields the computer and transceiver from RF energy, but does not remove RF energy from cables and wires. This method of suppressing RF energy is most effective if a powerful SDR transceiver such as the Flex SDR-3000 and Flex SDR-5000 is used, as well as if an external power amplifier is used.

A special case of RF grounding is the electrical grounding of the amplifier and transceiver housings. Through it, the RF potential will also effectively flow to the ground. Remember, if there is RF potential on the wires and housings during transmission, then it is also there for reception! This means that all interference that is in the reception area will be received not only by the antenna, but also by the cable and the housing of the transceiver and computer. Those. By moving the antenna outside the transmitter room, but without getting rid of HF interference, you will catch all the interference from this room.

In amateur radio practice, there are situations when there is no access to electrical grounding and the antenna is designed in such a way that during transmission literally all electrical wiring is “phonic”. For example, this could be a completely insulated glazed balcony and a “long rope of random size” antenna. In this case, such a wonderful box as “artificial earth” will help remove the potential from devices. What is she? Essentially, this is a small antenna made of a short wire (from 1 to 2 meters) tuned to resonance by LC circuits in a separate housing. This small antenna sucks the remaining potential from the transceiver body and re-radiates it into space elsewhere from the low-efficiency antenna. An analogy is a small vacuum cleaner that sucks out the dangerous liquid that has flowed from the cable from the body. Such devices can be connected not only to the transceiver, but also to a computer in particularly harsh electromagnetic operating conditions of the transceiver. The main thing is to move the main antenna away from these re-emitters. The American company MFJ produces ready-made “artificial soil” called.

Thus, if you have frequent problems with your computer not related to its contents, but related to the operation of the transceiver for transmission, then most likely these problems are associated with the presence of stray RF currents along the antenna cable, the housing of the transceiver and the computer. It is enough to properly build the antenna and ground everything, and these problems will disappear. You can check the nature of computer freezes by connecting it to the transceiver output instead of an antenna. If the computer freezes have stopped, then we make grounding and an antenna.

Software Defined Radio is a software-defined radio, a new trend in the construction of amateur radio designs, where some of the functions of the receiver (sometimes the transmitter) are transferred to a computer (microprocessor, microcontroller). Let's take a look at the block diagram:

The signal from the antenna enters the input circuits, where it is filtered from unnecessary signals, can be amplified or divided, it all depends on the tasks of the device. In the mixer, the desired signal is mixed with local oscillator signals. Yes, yes, exactly with signals! There are two of them, and they are out of phase by 90 degrees relative to each other.

At the output of the mixer we already have audio frequency signals, the spectrum of which lies from the local oscillator frequency above and below. For example: the local oscillator is 27.160 megahertz, and the frequency of the useful signal is 27.175 megahertz, at the output of the mixer we have signals with a frequency of 15 kilohertz. Yes! Two again. They are also called IQ signals. The audio amplifier adjusts the level to the desired level and feeds it to the ADC. Based on the phase shift of IQ signals, the program determines whether the useful signal was above or below the local oscillator and suppresses the unnecessary mirror reception band.
By the way, the SDR transmitter works on approximately the same principles: a phase-shifted low-frequency signal from the DAC is mixed with a local oscillator in the mixer, and at the output we have a modulated high-frequency signal, suitable for amplification in power and supply to the antenna.
It should also be noted that even more modern SDR systems have appeared, in which the useful signal is directly supplied to a high-speed ADC.

In amateur radio equipment of the lower and middle segment, computer sound cards are mainly used as ADCs. Both built into the motherboard and external, connected via USB or inserted into the PCI connector of the motherboard. The reason for this is simple: usually the sound cards built into the motherboard do not have good characteristics and this is compensated by installing external ones. The span (the band in which the sdr is able to receive a useful signal without tuning the local oscillator) directly depends on the sound card: the higher the frequency that the sound card can digitize, the wider the span. Typically these values ​​are 44 kilohertz (bandwidth 22), 48 kilohertz (bandwidth 24), 96 kilohertz (48) and even 192 (96) kilohertz. In high-end technology, high-quality and expensive ADCs are used, the signal from which is converted by a microprocessor built into the SDR to an understandable computer.
The main advantage of SDR technology in amateur radio practice: a large number of types of modulations, adjustable transceiver parameters (after all, signal processing is done in software) and a panoramic view of the range.

Since SDR transceivers and receivers are essentially direct conversion receivers and transceivers, it will be useful to familiarize yourself with the theory of the processes occurring in these devices. How exactly the required sideband is allocated or formed in SDR becomes clear after reading the document.

The most important advantages of SDR are an amazing panorama of broadcast events, when you don’t just stare blankly at a digital scale, but see and feel its real situation. The second quality is an “awesome” receiver, which for some reason does not hiss or make noise, allowing you to make any conceivable bandwidth without “chimes” and additional costs.

I first tried SDR in 2010. Since then, I have firmly saddled this horse and have no plans to get off it in the foreseeable future. No one is better - the expensive Yaecomwood/Elecraftor is no longer worthy of my ears. My only regret is that I didn't get around to doing this sooner. There was enough information, but I was confused by an inexplicable internal prejudice, as in all likelihood many are today.

Since almost all known SDR devices have been in my shack, I think I can give an inexperienced amateur advice on choosing a worthy purchase.

First generation SDR

It all started with the American Flex-1000. Thanks to the selfless efforts of a group of enthusiasts, among whom I would primarily like to mention RW3PS and UT2FW, SDR technology has become quite widespread throughout the CIS. Thousander clones appeared. I myself started with the model from UR4QBP. It was then that I realized - this is a dream radio and I need to move on. Thousanders and their numerous clones, of course, remain workable, but starting from the second version of the PowerSDR control program, FlexRadio no longer supports this series. Since progress is moving forward by leaps and bounds, I consider purchasing a Flex-1000 such a transceiver as a futile exercise. Among other things, you need to be deeply friends with HT.

The outgoing generation from FLEX

Flex-5000 undoubtedly the most advanced of the entire line. It has excellent receiver parameters, 100 watts of output power, and an auto tuner. Its special quality is the most powerful antenna selector, which allows you to switch antennas and additional converters, transceivers, receivers, splitters in the most unimaginable combinations. Plus the possibility of optionally expanding the transceiver with a second autonomous receiver (with the same high parameters) and a VHF/UHF transverter. In a word, EXTRA class. Two drawbacks. The first is the need to have a specific IEE1394 (FireWire) port on the computer. The second is the relatively high price. Basic configuration about 3td. (The company released the 5000C modification, which was a candy bar with a computer together. Firstly, it is insanely expensive. Secondly, this is a road to nowhere, because computer progress is so rapid that you can’t keep up with it. The computer built into the 5000C is antediluvian by today's standards).

Flex-1500 A small, cute device on a USB cord. For those who do not compete in competitions, for those who have a limited budget, this toy is just right. For 600-700 USD you get visually the same as in other SDRs - a gorgeous panorama no different from its older brothers. After all, the PowerSDR control program from FlexRadio is the same for the entire line of the 1000-1500-3000-5000 series. The receiver here is average, because... It is not the most advanced audio codec that is used, which mainly determines the quality indicators of the receiver (although how to look at it: in the rank of the QST Magazine Product Reviews table it is higher than the multi-kilobuck top models).

Flex-3000— in my opinion, the best option, the best choice in terms of price/performance ratio. At the beginning, a certain absurdity of his appearance repelled him from me, but this property turned out to be absolutely deceptive. The device fits perfectly on my desktop and is now my main one. The receiver is almost the same as the older model 5000. The span is smaller, it is 96 kHz versus 192 kHz for the Flex-5000. But, by the way, 96 kHz is the most convenient span. It also works well with digital programs. At the transmitter output we have 100-120 watts and an auto-tuner, which is a plus in the absence of antennas. The device is very unpretentious and can be easily disassembled for cleaning and repair, if necessary. I'll add. To reduce the noise level, I replaced the cooling fans. Now the transceiver is practically inaudible.

Let me note that there were no clones of this generation from our craftsmen, because... In addition to the hardware circuits, Firmware control microprograms were required, and this apparently turned out to be inaccessible and unaffordable.

New generation SDR

Based on the technique of direct digitization of the radio frequency signal - DDC. The leader here is undoubtedly the open source HPSDR project, which began its journey with the publication of Phil Harman VK6APH (now VK6PH) in 2008 and was first presented at the Dayton Hamvention in 2010. The result of the project was a single-board transceiver HERMES, on the basis of which a number of completed designs have been made: Indian Anan and Angelia, Ukrainian DUCSI.VD, Voronezh design with a 300-watt amplifier, and, probably, there are other manufacturers. The device is super. By obtaining the HERMES board and attaching any suitable amplifier to it, the shortwave radio operator receives an unrivaled tool for on-air work. A small board (up to 10-15 watts) can be built into the hard drive bay of a computer and powered from the same power supply. This results in a wonderful monoblock. An additional plus is that the control program is built on the basis of PowerSDR, which allows the operator not to have to retrain or adapt to a new way. There is a built-in ability to control the transceiver using the HERCULES media remote control. A number of interesting programs and useful programs have been created for HERMES by third-party programmers. One of them is HermesVNA, which turns the transceiver into a high-precision vector analyzer (analogous to multi-kilobuck devices). Nowadays, HPSDR adherents have begun to master the technology of linearization of amplifiers using distortion compensation. You can read, watch and “touch” it at this link. The effect is stunning.

Taganrog radio amateur designers created a Russian DDC transceiver SunSDR2. The principle of operation is the same, the details are different. But the software shell has a different appearance, to which the previous owner of Flex-like systems will have to adapt. But in the end, it's a matter of taste and habits. The hardware itself is wonderful, it has a great future for software development. We cannot discount the fact that this is a domestic manufacturer, which means warranty and post-warranty service will not be burdensome. For information: a trivial repair of a Flex-5000 in the States cost my friend half a grand. At the same time, it is worth paying attention to an interesting article by RN3KK.

Interesting development of DDC transceiver ZS-1 from St. Petersburg. Although the dynamic qualities of the receiver are higher than those of the Taganrog model, there is also an undoubted drawback - the lack of a built-in DAC, which leads to noticeable signal delays during its processing.

However, the Zeus Radio program is currently under active development and who knows what will happen next. The desire of the authors to make it multi-platform is respectable. The guys from St. Petersburg are striving for development.

Italian should appear on the market in the coming days DDC transceiver FDM-DUO, which allows you to work without a computer, i.e. has a built-in DSP unit and a control microcomputer.

What about the legendary Flex?

The company launched a line on the market in 2013 DDC transceivers 6000 series. The processing principle is the same as in HPSDR. Unfortunately, the manufacturer's pricing policy is aimed at wealthy buyers. The software has not been fully developed and the first fully functional version of SmartSDR is expected only by the end of 2014 and will be paid for subsequent updates.

I see that HPSDR clones will soon be sold like pie on the market by a variety of manufacturers, including guys from the Middle Kingdom. So most likely the pricing policy of Flex will have to change.

At the end of April 2014 the smallest one appeared (100x75mm) DDC transceiver HiQSDR-mini from David Fainitski from Germany, which was originally conceived as a clone of the well-known HiQSDR, but later the circuit design departed significantly from the original. According to the author, this will be the cheapest SDR DDC transceiver to date.

The background of HiQSDR-mini was the Minor SDR DDC receiver of the same author with PCB dimensions 90x60mm. The receiver is great, there are no words. Works great under PowerSDR (by OpenHPSDR). Implementation of VAC&CAT - 100%. Built-in support for Hercules DJ Control. What I really liked: minimal signal processing delay (compared with IC-756, signals are almost equal). This delay can be neglected even when receiving high-speed CW.

In July 2014, David prepared the final version of Minor ver.1.7 for release. Significant upgrades have been added to the receiver to further improve the quality of reception, incl. and bandpass filters at the input. The size of the receiver in the case, along with its highest parameters, is admirable, only 98x70mm. This is one and a half times smaller than my mobile phone. The price of the receiver is very affordable and today it is the cheapest DDC RX of this class on the world market (250 USD).

As you might expect, Flexradio Systems launched the 6300 model at a more or less reasonable price of $2,499.00. That is, this is a kind of similarity to the Flex-3000 from the previous line. The parameters are almost the same as those of the older brothers 6000, but without frills and baubles. But useful options such as an autotuner, a remote control with a valcode and control buttons will have to be purchased for a separate fee. I'm pleased with the free delivery, although it's not clear whether it applies to the whole ball or just the states.

Boris RW6HCH purchased a ready-made HiQSDR-mini board and built a complete DDC transceiver on its basis:

I was pleased with the result.

Conclusion

If you want to try SDR technology and not fool yourself with computer and network knowledge, start with the inexpensive but cool Afedri DDC receiver (download/launch the free program and work - almost plug-n-play). It can also be used in conjunction with a conventional transceiver. A very suitable and more advanced option for solving this problem could be the Minor DDC receiver, which has higher dynamics and a lower signal processing delay. If you want to immediately switch to SDR, there is a direct path to a suitable DDC transceiver design. It's all about your capabilities.

There is a lot of talk about the difficulties of using SDR in competitions. Basically they come from those dogmas who have only seen SDR in pictures. Without going into details, I will emphasize that it is SDR that provides unique opportunities for participation in competitions, which a traditional chest does not have in principle. Just to name a few, victory in the Russian Cup, victory in the SAC contest, victory in the Southern Federal District championship, victory in the CQ-M subgroup, a number of prizes in quite prestigious competitions in 2012, etc., etc. Although I am not a contester in the full sense of the word. So-so, just fussing for old time’s sake 😉

The SDR owner should pay attention to the computer and monitor. The first one must be quite high-performance and trouble-free. The second with maximum physical dimensions and resolution in order to accommodate as many windows as possible with running programs on one screen. I use a 27″ monitor with a matrix resolution of 2560x1440. Although I love a laptop, I consider it unsuitable for an amateur radio shack.

Today, an amateur radio station should not be built on the basis of a transceiver (as many mistakenly believe), but on the basis of a good computer that connects all devices of the radio station, the Internet, and the operator into a single information and communication field and allows solving amateur communication problems at the most modern level.

Good luck. 73,
de R6YY

Fans of the group PELAGEYA ("Polefans") VKontakte

Concert on Minin Square in Nizhny Novgorod May 9, 2013

Mini-concert in Magas (Ingushetia) June 4, 2014

Create a topic (if it has not already been created) on the forum http://ra3pkj.keyforum.ru

SDR HAM - Introduction

Attention! In winter, the CY7C68013 microcircuit may fail due to breakdown by static electricity, which accumulates in the air and on surrounding objects, and then flows down an unpredictable path. It is necessary that the equipment is grounded, and the SDR ground bus is connected to the computer case with a separate wire. Touch boards and parts on boards that are connected to the equipment only after removing static electricity from your hands, for example, by touching massive metal objects. I STRONGLY recommend connecting the USB connector body (which is on the SDR board) directly to the SDR ground bus, for which you need to short-circuit the parallel circuit C239, R75 (near the USB connector).

To purchase blank boards, contact Yuri (R3KBL) [email protected]

I’ll say right away that I did not make this transceiver, I’m just interested in the topic itself and the results. Moreover, the transceiver uses an AD9958 synthesizer of my design, and I also wrote new firmware for the USB adapter integrated into the board, which replaced the original outdated firmware “from the German” (this is discussed below).

general information

The SDR HAM transceiver is a clone of the SDR-1000, structurally designed by Vladimir RA4CJQ. The transceiver uses well-known circuit solutions developed by many radio amateurs. The difference from the well-known “Kyiv” clone SDR-1000UA is quite noticeable. Brief description of features:

1. Single board design.

2. Transmitter power amplifier of at least 8 W (those with talent can squeeze out more).

3. Frequency synthesizer on the DDS AD9958 chip with a low level of spurs (the synthesizer is described here:).

4. Transceiver control via USB ( The USB adapter is structurally described here: but there is special firmware for SDR-HAM!!!).

5. Power supply: +13.8V and bipolar +-15V.

6. Two-stage relay attenuator at the receiver input.

7. SWR and power meter.

8. Work without brakes in ANY Windows operating systems without installing a driver (the system HID driver of Windows itself is used), which became possible after replacing the firmware of the USB adapter integrated into the board (this is discussed below).

Information about firmware and software

The transceiver works with official PowerSDR from FlexRadio Systems versions no higher than 2.5.3 (starting from version 2.6.0, the SDR-1000 transceiver and its clones are not supported), but works with PowerSDR 2.8.0 from KE9NS, which in turn was adapted for SDR -1000 radio amateur Excalibur (the latest in fashion). Here's more about this version 2.8.0.

The AT91SAM7S controller (used to control the AD9958 synthesizer) should be flashed as described here:.

Now let's talk about the firmware and 24C64 memory chips, which are necessary for the CY7C68013 controller to function as a USB adapter. Historically, when the transceiver went to the masses, the firmware of the USB-LPT adapter from the “German” (described on my website) was “poured” into the memory chip (described on my website), but as it turned out, in versions of Windows higher than Windows 7-32, the firmware is humanly does not work. Brakes and problems with the digital signature of the driver!!! (owners of Windows XP and Windows 7-32 can sleep peacefully). The problem was solved after I wrote a new firmware that works in any operating system without any problems and also does not require driver installation (Windows itself will find an HID driver in its bins). The firmware was created by me in collaboration with US9IGY.
But there is a nuance - reflashing the memory chip located onboard, requires exercises with a soldering iron, since it involves lifting one leg of the microcircuit and connecting a temporary toggle switch (this will be discussed below). Flashing a CLEAN microcircuit into a board (i.e. in a freshly manufactured transceiver or when a memory chip is installed from a store) does not require additional exercises with a soldering iron. Both options for your behavior are described below:

1. A blank 24C64 memory chip should be flashed as described here: except that a special new firmware is used and the main working driver mentioned at the end of the page is not installed. Download the new firmware sdr_ham.iic: sdr_ham.zip. The firmware is flashed into the transceiver itself via USB (the same archive contains the sdr_ham.hex firmware for those who want to flash the memory chip outside the transceiver, i.e. using a programmer). Before flashing, do not forget to move the jumper on the board (which is about 24C64) to the programming enable position, and also do not forget to return it to its original position after flashing.

2. whoever will reflash the 24C64 memory chip (which has old firmware from the “German”) must do everything the same as described above in paragraph 1, but taking into account the following: temporarily unsolder pin 5 of the 24C64 chip (we pretend that we have clean microcircuit) and connect it via a toggle switch, move the jumper on the board (which is about 24C64) to the programming enable position and, with the toggle switch open, connect the SDR to the USB socket of the computer. Next, turn on the power to the SDR and run the flash program. Immediately before flashing, close the toggle switch. After flashing, turn off SDR and restore everything back.

For reference. The SDR (or rather its USB adapter) is defined by the computer as an HID Device, the properties of which have the following ID values: VID_0483 and PID_5750.

After all the hassle of flashing is completed, you can safely exhale and calmly place the Sdr1kUsb.dll file from RN3QMP in the folder with PowerSDR - download sdr1kusb_rn3qmp.zip. In PowerSDR, in the General -> Hardware Config menu, check the "USB Adapter" box.

Information for owners of various other SDR transceivers!!! In the firmware of the 24C64 memory chip (for CY7C68013), I limited myself to only what is necessary for SDR HAM. The firmware is not intended for upgrading USB adapters to CY7C68013 for SDR-1000 with DDS AD9854. This is confirmed by the UR4QOP experiment in the transceiver from UR4QBP - DDS AD9854 does not work! So I can state that the firmware is intended only for SDR HAM. I don’t have the time or motivation to adapt anything in the firmware for other applications (except for SDR-HAM).

Clean boards from yuraws

Clean boards with hole plating, solder mask and markings.

Straight side:

Back side:

Scheme

Download and unpack the diagrams (as well as drawings of the board on both sides) in PDF format: sdr_ham_shema_pdf.7z The same diagrams are shown below for general reference.

Input attenuator, UHF:

Range bandpass filters (in the diagram the Amidon rings are indicated in color - red T50-2, yellow T50-6):

Mixers, receiver and transmitter amplifiers:

Automatic control_1:

Automatic control_2:

Frequency synthesizer:

USB/LPT adapter:

Microcontroller for controlling the frequency synthesizer:

Transmitter power amplifier and ADC for SWR and power meter:

Pay

High-quality board drawings in PDF format are in the same document as the schematics (download in the previous paragraph). Below is a general view for your reference:

Design project

Download the project (with schematic and board): project_sdr_ham.7z AltiumDesignerViewer viewer on the official website: http://downloads.altium.com/altiumdesigner/AltiumDesignerViewerBuild9.3.0.19153.zip

List of elements

The list from RA4CJQ is generated automatically by the PCB layout program, so the names of many elements are not specific, but conditional. Keep in mind that such names are often not suitable for ordering items in stores. Download the list of elements in Excel 2007-2010 format: sdr_ham.xlsx.

List from Steve (KF5KOG). This list also includes links to Mouser and Digikey stores (item names are clickable). The catalog names of these stores are indicated (they differ slightly from the names of the element manufacturers themselves): Parts List with Manufacturer part Numbers 18 Sep 2014.pdf

Bugs and improvements

Sometimes radio amateurs post messages on forums about noticed errors, and also suggest various improvements. I will publish them here as soon as possible.

#1. On the board, the positional designations of resistors R90 and R94 in the wiring of one of the transistors RD06 of the power amplifier are mixed up. The figure shows the correct designation (resistors are marked with highlight):

#2. In the UHF circuit, in the power circuit of the DA1 AG604-89 microcircuit, resistors R5 and R6 should be 130 Ohms each.

#3. It has been repeatedly reported that on clean boards from the manufacturer (link to the manufacturer at the top of the page) there are shorts in the area of ​​the DFT elements. Moreover, the resistance of the shorts can be very different, for example, several Ohms and higher. In reception mode this is not particularly noticeable to the ear, but during transmission the output power is low. Shorties were also found in the area of ​​the INA163 microcircuits, which was expressed in an imbalance of the signals supplied to the left and right channels of the sound card. Often short spots are not visible even at high magnification. In such cases, the short ones must be “burned out” with an electric current of low voltage but sufficient power.

#4. Please note that the DD6 chip on the board is initially rotated 180 degrees. compared to microcircuits DD4, 8, 9. That's right! You can mechanically solder DD6 in the same way as DD4, 8, 9 and this will not be correct.

#5. The transceiver requires an external bipolar voltage of +-15V (in addition to the +13.8V voltage) for power supply. In principle, it can be powered from a +-15V transformer source, but many radio amateurs use DC/DC converter microcircuits, putting up with a slight increase in noise from such converters. To do this, a scarf is made on which the microcircuit and wiring elements are soldered, and the scarf itself is placed on the transceiver board. They use MAX743 microcircuits (a converter from +5V to +-15V), link to the datasheet http://datasheets.maximintegrated.com/en/ds/MAX743.pdf, the datasheet contains a drawing of a printed circuit board, the wiring of the microcircuit is quite complex. They also use microcircuits P6CU-1215 (from +12V to +-15V) or P6CU-0515 (from +5V to +-15V), which require fewer wiring elements, link to the datasheet http://lib.chipdip.ru/011/DOC001011940 .pdf. Also mentioned are the RY-0515D and NMV0515S microcircuits (both from +5V to +-15V), the latter makes little noise. It must be said that when using converters from +5V to +-15V, an enlarged radiator is required for the +5V stabilizer, because The current consumption of the converters is noticeable.

#6. To obtain an output power of 10W (or more), you should replace the RD06HHF1 transistors with RD16HHF1. Set the quiescent current of each transistor to 250mA. If the size of the radiator allows, then the quiescent current can be made significantly larger. Stew KF5KOG in the yahoo group suggests changing the values ​​of the wiring elements of these transistors. Change capacitors C254,268 to 0.1 μm, and change resistors R91,102 to 680 Ohms.

#7. The HF transformer on the BN-43-202 binoculars at the output of the power amplifier gets very hot. It is proposed to replace the core with tubes 2643480102 FERRITE CORE, CYLINDRICAL, 121OHM/100MHZ, 300MHZ. Dimensions Dext.12.3mm x Dint.4.95mm x Length 12.7mm, material-43. Datasheet http://www.farnell.com/datasheets/909531.pdf (the photo on the right shows the previous transformer on the binoculars for comparison):

Stew KF5KOG in the yahoo group suggests replacing the core with a BN43-3312. Change capacitor C261 to 100pF, while the output power on the 6m range is at least 8W (using RD16HHF1 transistors). Secondary winding 3 turns!

A radio amateur with the nickname Lexfx (CQHAM forum) solved the problem differently. He installed an additional choke (in red in the diagram), while the middle output of the binoculars is no longer used. Choke core 10x6x5mm (probably 1000NN), 7 turns in two wires with a diameter of 0.8mm:

#8. Information from the yahoo group. To reduce UHF noise, you need to cut off the ground trace in one place (Bridge gap in the picture), and add SMD inductance in another place, breaking the conductor in this place (Cut Trace in the picture):

#9. To level out the noise track in the PowerSDR panorama, it is recommended to reduce the capacitance value of capacitors C104, 107, 112, 113 (at the outputs of the FST3253 receiver mixer) to 0.012 microns or even to 8200 pf.

#10. Error when wiring the board. Pins 2.3 (source, drain) of transistor VT2 IRLML5103, which supplies power to the UHF chip, must be swapped. Decide for yourself how to do this. Possibly wires. Datasheet IRLML5103.pdf

#eleven. Unsuccessful power amplifier bypass circuit. When switching to transmit, the bypass cable remains connected to the amplifier input, which drives the amplifier at 50 MHz. It is suggested to use the free contacts of the K26 relay to completely disconnect the bypass cable. Relay K26 has two groups of contacts. We unsolder K26 (if it was already soldered) and perform it according to the diagram and figure below. We use PEV winding wire for jumpers. You may have to bend the relay legs a little before soldering. It will be almost unnoticeable. On a fragment of the board, white lines show where the tracks are cut, and thin black lines show wire jumpers:

The radiator is an aluminum plate 3...4 mm thick, fixed to the bottom of the board on racks. The power amplifier transistors and the +5V stabilizer are soldered on the back side of the board and screwed to the heatsink.