---

1. 5 RF Transmitter Measurements Every Engineer Should Know
   
   
    

   ---

2. ZigBee Alliance Launches Smart Energy Profile 2.0 For HANs
   
   The ZigBee Alliance has finalized its Smart Energy Profile 2.0 (SEP2) standard, which is an application for short-range radios using the ZigBee standard for wireless networking. It implements all the various features needed for home energy management.
                       

   ---

3. Understanding Signal Analyzer Architectures
    

   Many engineers who use spectrum analyzers on a regular basis might be content to know that their instruments will produce a display of “power versus frequency” with little idea of what’s going on inside. Despite this, understanding the architecture of these instruments is important to maximizing their performance in practical applications.

   An RF signal analyzer must downconvert signals from RF to a frequency range that can be digitized with an analog-to-digital converter (ADC) with anywhere from 12 to 16 bits of resolution. The mixer—and its frequency translation properties—is at the heart of the downconversion process, though I won’t focus on mixer theory of operation here (see “What’s Inside Your RF Signal Analyzer?”). Instead, I want to focus on two main vector signal analyzer (VSA) architectures, exploring both the theory of how they downconvert signals to baseband and the tradeoffs between them.

   
    

   ---

4. The Fundamentals of Oscilloscope Triggering
   
    

   A trigger is defined as “anything, as an act or event, which serves as a stimulus and initiates or precipitates a reaction or series of reactions.” The same definition applies to an oscilloscope trigger. An oscilloscope trigger involves waiting for an event to occur, triggering upon occurrence of the event, and then the oscilloscope capturing and displaying the electrical signaling (data) that follows the trigger event. For more complex events, it’s important that an oscilloscope incorporate advanced triggering capabilities. Overall, oscilloscope triggers have become important to the point where they’re often the deciding factor when purchasing an oscilloscope.

   • The Importance Of Triggering
   • The Edge Trigger
   • Edge-Trigger Limitations
   • Advanced (Smart) Triggers
   • Runt Triggering
   • Setup-And-Hold Triggering
   • Pulse-Width Trigger
   • Software Trigger
     
     
      

     ---

5. Essential Steps For Making High-Quality Electrical Measurements
   
   Accurate measurements are central to virtually every scientific and engineering discipline, but measurement science tends to suffer for a couple of reasons. For one, it musters little attention in the undergraduate curriculum. Secondly, even for those engineers who received a thorough grounding in measurement fundamentals as undergraduates, it’s certainly possible—and forgivable—if they’ve forgotten some of the details.
   
    

   ---

6. Understanding Onboard Flash Programming
   
   Firmware often is preprogrammed into flash memory devices prior to the printed-circuit board’s (PCB) manufacture to maintain high throughput and avoid slowing the manufacturing beat rate. Yet there are advantages to programming the flash memory after it has been soldered to the PCB. In-circuit test (ICT), the Joint Test Action Group (JTAG) interface, and external connectors all can be used to program flash devices without impacting manufacturing beat rates. Image size, existing manufacturing infrastructure, system capability, and required programming methods also should be considered in choosing an optimal preprogramming solution.
   
    

   ---

7. Software Defined Radio Handbook
   
   SDR (Software-Defined Radio) has revolutionized electronic systems for a variety of applications including communications, data acquisition and signal processing. This handbook shows how DDCs (Digital Downconverters) and DUCs (Digital Upconverters), the fundamental building blocks of SDR, can replace legacy analog receiver and transmitter designs while offering significant benefits in performance, density and cost. In order to fully appreciate the benefits of SDR, conventional analog receiver and transmitter systems will be compared to their digital counterparts, highlighting similarities and differences. The inner workings of the SDR will be explored with an in-depth description of the internal structure and the devices used. Finally, some actual board- and system-level implementations and available off-the-shelf SDR products and applications based on such products will be presented.
   
   
   
    

   ---

8. PCBWeb, The Latest PCB Design Tool to Hit the Web
   
    

   Several browser-based PCB design tools have emerged in the past couple of years, yet the vast majority of designers are still using the same desktop applications that have dominated the EDA industry for decades.

   Now PCBWeb, a new design tool from the founders of Aspen Labs, the media company behind the electrical engineering community EEWeb, is the latest product to be introduced into this competitive space. Their goal? To provide a full-featured online circuit design and manufacturing solution for professional engineers.
   
   
    

   ---

9. Circuit Generates High-Frequency Sine/Cosine Waves From Square-Wave Input
   
   Although quite a few direct digital synthesis (DDS) ICs can generate high-frequency sine waves, their complexity excludes them from many designs. However, designers can use simple high-frequency CMOS logic and two switched-capacitor filters to create a sine/cosine generator. With newer filters, a 1-MHz output at 1.7 V p-p is possible.
   
   The example circuit uses an MSHFS6 5-V, low-power 12.5:1 switched-capacitor filter with selectable Butterworth, Bessel, or elliptic filters in the lowpass mode and full-, 1/3-, or 1/6-octave filters in the bandpass mode. Since the lowpass mode would cause a 3-dB loss of the signal output, the circuit uses the 1/6-octave bandpass filter, which is selected by tying pins 1 and 3 high on the MSHFS6 (Fig. 1).
   
   
    

   ---

10. Understanding The Internet Of Things
    
    Recent developments in connectivity technologies have spurred the adoption of Internet-connected “smart” devices for remote sensing, actuating, and intelligent monitoring using advanced analytics and real-time data processing. As the pace and the scale of such solutions increase rapidly, there will soon be a problem getting these disparate solutions to work seamlessly together to realize a large-scale Internet of Things (IoT). Recent developments in protocols and standardization initiatives for the IoT, particularly application layer protocols, aim to address these issues.
    
    
     

    ---

11. Understanding Wireless Range Calculations
    
    One of the key calculations in any wireless design is range, the maximum distance between transmitter and receiver for normal operation. This article identifies the factors involved in calculating range and shows how to estimate range to ensure a reliable communications link.
     

    Since dBm is based on a logarithmic scale, it is an absolute power measurement. For every increase of 3 dBm there is roughly twice the output power, and every increase of 10 dBm represents a tenfold increase in power. 10 dBm (10 mW) is 10 times more powerful than 0 dBm (1 mW), and 20 dBm (100 mW) is 10 times more powerful than 10 dBm.

    You can convert between mW and dBm using the following formulas:

    P(dBm) = 10 · log₁₀(P(mW))

    P(mW) = 10^(P(dBm)/10)

    For example, a power of 2.5 mW in dBm is:

    dBm = 10log2.5 = 3.979

    or about 4 dBm. A dBm value of 7 dBm in mW of power is:

    P = 10^7/10 = 10^0.7 = 5 mW

    
    
     

    ---

12. Understanding Lithium Battery Tradeoffs In Mobile Devices
    
    Lithium-ion (Li-ion) batteries give mobile-device designers choices that affect product convenience, durability, and style. These choices involve tradeoffs among several parameters, though (see the table). Understanding how these factors interact requires some knowledge of Li-ion construction and chemistry.
    
    
     

    ---

13. Fundamentals of Communications Access Technologies: FDMA, TDMA, CDMA, OFDMA,
    AND SDMA
    
    Access methods are multiplexing techniques that provide communications services to multiple users in a single-bandwidth wired or wireless medium. Communications channels, whether they’re wireless spectrum segments or cable connections, are expensive. Communications services providers must engage multiple paid users over limited resources to make a profit. Access methods allow many users to share these limited channels to provide the economy of scale necessary for a successful communications business. There are five basic access or multiplexing methods: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and spatial division multiple access (SDMA).
    
    
    
    
    
    
    
    
     

    ---

14. An Introduction to LTE-Advanced: The Real 4G
     

    Long-Term Evolution (LTE) is being adopted around the world as the primary cell-phone communications service. Multiple 2G and 3G cellular radio methods are being phased out as carriers build their new LTE networks. It will be years before this expansion is complete, and older radio technologies like GSM and CDMA will coexist with LTE for a while (see “The Evolution Of LTE,” www.demo.electronicdesign.com/content/evolution-lte ).

    LTE is likely the most complex wireless system ever developed. It incorporates features that could not have been economically implemented as recently as a decade ago. Today, with large-scale ICs, LTE can be easily accommodated in basestations and battery-powered handsets alike. The complexity is a function of the advanced wireless methods used as well as the many options and features that can be implemented.

    In the meantime, the next phase of the LTE standards as put forth by the Third Generation Partnership Project (3GPP) is ready to be deployed.¹ Called LTE-Advanced (LTE-A), this significant upgrade to the LTE standard will provide more speed and greater reliability. While LTE-A is still being developed, some LTE-A service could begin late in 2013.
    
     

    ---

15. Raise Your Decibel Awareness In Audio Measurements
    
    In the radio-frequency (RF) microwave test and measurement world, engineers often deal with the power measurement unit of dBm instead of wattage (W). However, when entering the audio measurement arena also need to understand the unit dBu, which is decibel (dB) relative to 1 mW into 600 Ω.
    
     

    The dBm unit is defined as:

    

    if a 600-Ω load results in 0 dBm. Therefore:

    

    Therefore:

    

     

    The “u” in dBu represents the word “unloaded.” It also implies that the load is un-terminated, or the load impedance is unspecified, and will likely be high. Thus, the 0.7746 V rms is an open circuit source.
     

    ---

16. The Fundamentals Of Short-Range Wireless Technology
     

    Wireless has become a major feature for just about every new electronic product. It adds flexibility, convenience, and remote monitoring and control without expensive wiring and cabling. The range of applications is staggering, from simple toys to consumer electronic products to industrial automation.

    This great rush to make everything wireless has produced a flood of different wireless technologies and protocols. Some were established primarily for one application, while others are more general and have many uses.
    
    

    ---

17. How Do Operational Amplifiers Operate?
    
    Though sometimes taken for granted, designers shouldn’t overlook the intricacies of voltage- and current-feedback op amps—integral players in the analog and mixed-signal worlds. Op amps amplify tiny signals from sensors so analog-to-digital converters (ADCs) can digitize them. They also make it possible to craft active filters with better characteristics than filters built of just coils and capacitors. Although an IC op amp’s circuitry tends to be subtle and complex, its application principles—at least to a first approximation—are relatively simple.
    
    
     

    ---

18. Understanding Trusted Computing From The Ground Up
    
    Why is trust related to computing such a big deal? Imagine if the data on your computer is visible to others. Or, what if others have changed the data on your computer? Trust doesn't only refer to "secrets," it also encompasses the ability to count on your computer to act the way you expect it to, without unanticipated crashes and appearance of viruses becoming part of your computing routine. These issues have made "trusted computing" the electronics industry's biggest 21st-century buzzwords.
    
    
     

    ---

19. Fundamentals Of Crystal Oscillator Design
     

    Appropriately cut quartz crystals can be used as high-quality electromechanical resonators. Their piezoelectric properties (voltage across the crystal deforms it; deforming the crystal generates a voltage) allow them to be the frequency-determining element in electronic circuits. Crystals are widely used in oscillators, timebases, and frequency synthesizers for their high quality factor (QF); excellent frequency stability; tight production tolerances; and relatively low cost.

    This article covers the primary design considerations for fundamental-mode oscillators using AT-cut crystals. These include load capacitance; negative resistance; startup time; frequency stability versus temperature; drive-level dependency; crystal aging; frequency error; and spurious modes. This information is based on experience from more than a decade designing ISM-band (industrial, scientific, medical) radios. (Topics relevant in other types of radio systems, such as crystal oscillator phase noise, aren’t limiting factors in ISM radios and aren’t covered.)

    • Crystal Modeling Basics
    • Load Capacitance
    • Negative Resistance
    • Startup Time
    • Frequency Stability versus Temperature
    • Aging
    • Compilation of Frequency Error Sources
    • Drive-Level Dependency
    • Spurious Modes
    • References

    ---

20. Relate ADC Topologies And Performance To Applications
    
    Don’t believe the hype. The digital revolution hasn’t conquered everything. We still need analog technologies to gather data and turn it into ones and zeroes, and the analog-to-digital converter (ADC) remains the foundation of that process. Different topologies (or architectures) are available for particular applications, though, so choose your ADC wisely (see “The Real World Versus Your ADC”).
    
     
     

    ---

21. The Real World Versus Your ADC
    
    Sensors that measure real-world variables seldom have output signals that can be directly connected to a data converter in a system. Typically, there are requirements to amplify, filter, shift offset, and perform other conditioning functions. Various device families perform these analog signal processing functions, each with unique strengths and application requirements.
    
     
     

    ---

22. Microcontrollers Tackle Networking Chores
    
    Developers have a range of wired and wireless mechanisms to connect microcontrollers to their peers (Table 1). On-chip peripherals often dictate the options, but many of the interfaces are accessible via off-chip peripherals. External line drivers and support chips are frequently required as well.
    
    
    
    An I²C network uses two control lines and is typically implemented using open drain drivers. There is a range of I²C protocols based around 7-bit and 10-bit device addressing.
    
     

    ---

23. How To Create And Program USB Devices
    
    The Universal Serial Bus (USB) standard has been with us for many years, but making USB devices is still a daunting task. The USB specification comprises thousands of pages spread over dozens of documents, and although good books have been written on the subject, they are rarely shorter. In addition, the application programming interface (API) offered for programming USB devices is often complex and intricate. This article describes how to program your own software-based USB devices. It is not limited to standard class devices, but also presents a way to implement any device, whether it complies with a standard class or not.
    
    
    
    
     

    ---

24. Understanding MPEG Audio Codecs From mp3 To xHE-AAC
    
     

    ---

25. Understanding HTML5
    
     

    ---

26. Get More Out Of Your Digital Oscilloscope
    
     

    ---

27. The Fundamentals Of Spectrum Analysis
    
    The analysis of electrical signals, otherwise known as signal analysis, is a fundamental challenge for virtually all electronic design engineers and scientists. While it provides valuable insight into a signal’s properties, signal analysis is only as good as the instrument with which it is performed. Spectrum analyzers and vector signal analyzers are two instruments commonly employed to analyze electrical signals. This tutorial covers the basics of how to make the best use of these instruments.
    
     
     
     

    ---

28. Understanding Amplifier Operating "Classes"
    
    “Class” is in session. This discussion of electronic amplifier circuits offers an overview of the characteristics that define commonly used class designations. The class designations described are A, B, AB, C, D, E, F, G, and H.

    • Amplifiers and Their Applications
    • Background of the Class Nomenclature
    • Amplifier Classes (Short Summary)
    • Classes A, B, and AB (Detailed Descriptions)
    • Class B and Bridge-Tied Load Amplifiers
    • Classes G and H
    • The Doherty Amplifier
    • Class C
    • Classes E and F
    • Class D
    • References

     

    ---

29. The Fundamentals Of Flash Memory Storage
    
    
     

    ---

30. Back to Basics: Impedance Matching (Part 1)
     

    The term “impedance matching” is rather straightforward. It’s simply defined as the process of making one impedance look like another. Frequently, it becomes necessary to match a load impedance to the source or internal impedance of a driving source.

    A wide variety of components and circuits can be used for impedance matching. This series summarizes the most common impedance-matching techniques.
    

    Fig 1. Maximum power is transferred from a source to a load when the load resistance equals the internal resistance of the source.
    

    Fig 2. Varying the load resistance on a source shows that maximum power to the load is achieved by matching load and source impedances. At this time, efficiency is 50%.
     

    ---

31. Back to Basics: Impedance Matching (Part 2)
    
    During impedance matching, a specific electronic load (R_L) is made to match a generator output impedance (R_g) for maximum power transfer. The need arises in virtually all electronic circuits, especially in RF circuit design.
    
    
     

    ---

32. Back to Basics: Impedance Matching (Part 3)
    
    The L-network is a real workhorse impedance-matching circuit (see “Back to Basics: Impedance Matching (Part 2)” ). While it fits many applications, a more complex circuit will provide better performance or better meet desired specifications in some instances. The T-networks and π-networks described here will often provide the needed improvement while still matching the load to the source.
    
    
     

    ---

33. Understanding Noise Terms In Electronic Circuits
    
    
     

    ---

34. Understand Signal Analysis In The Time, Frequency, And Modulation Domains
     

    Modern oscilloscopes capture, view, measure, and analyze complex RF signals in the time, frequency, and modulation domains. Time-domain analysis, the original oscilloscope function, allows users to see the signal’s modulation envelope. It also enables measurement of signal-transition times, overshoot, and other time-related characteristics.

    The frequency-domain view shows the signal’s spectral content, the power distribution as a function of frequency. The modulation-domain view allows us to demodulate the signal and view the modulation data. This multi-domain analysis capability reduces the number of test instruments required to completely characterize signals and provides a simultaneous view of all domains.

    We will look at a couple of examples of signals that benefit from this multi-domain analysis and show a comprehensive view of the three domains.

    
     

    ---

35. Fundamentals Of Low-Power Design
     

    In the realm of design, the quest for low power continues ad infinitum as a primary goal. Yet low-power requirements place significant additional constraints on designs, constraints that ordinarily would be secondary or non-existent. Often, a simple oversight in the firmware executing on a part can substantially reduce battery life.

    When on this quest, designers must ask—before writing any code, selecting components, or creating schematics—what “low power” means. Almost always, the answer is that it depends. For instance, it depends on the application, the typical use case, and a whole slew of tradeoffs involving cost, performance, size, and other factors.

    
     

    ---

36. Understanding Modern Digital Modulation Techniques
    
     

    Fundamental to all wireless communications is modulation, the process of impressing the data to be transmitted on the radio carrier. Most wireless transmissions today are digital, and with the limited spectrum available, the type of modulation is more critical than it has ever been.

    The main goal of modulation today is to squeeze as much data into the least amount of spectrum possible. That objective, known as spectral efficiency, measures how quickly data can be transmitted in an assigned bandwidth. The unit of measurement is bits per second per Hz (b/s/Hz). Multiple techniques have emerged to achieve and improve spectral efficiency.

    Table of Contents

    • Amplitude Shift Keying (ASK) and Frequency Shift Keying (FSK)
    • Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK)
    • Data Rate And Baud Rate
    • Multiple Phase Shift Keying (M-PSK)
    • Quadrature Amplitude Modulation (QAM)
    • Amplitude Phase Shift Keying (APSK)
    • Orthogonal Frequency Division Multiplexing
    • Determining Spectral Efficiency
    • Other Factors Affecting Spectral Efficiency
    • Implementing Modulation And Demodulation
    • The Pursuit Of Greater Spectral Efficiency
    • Acknowledgment
    • References

    

    
     

    ---

37. Use Li-Ion Batteries In Your Next Mobile Computer
     

    Lithium-ion (Li-ion) cells come in three basic form factors: cylindrical, prismatic (rectangular brick shape), and flat lithium-polymer (LiPo) cells. The most commonly used Li-ion cell is the cylindrical 18650 cell (Fig. 1). Several million cells per month are manufactured, and they’re used in most notebook computer applications.

    The 18650 offers the lowest cost per watt hour. The “18” refers to the cell diameter in millimeters, and the “650” means it’s 65 mm long. Li-ion cylindrical (and prismatic) material layers are rolled like a jelly roll. Li-ion cylindrical (and prismatic) cells are packaged in metal cans. Typical capacities of an 18650 cell range from 2.2 to 3.0 Ahrs.

    Prismatic or brick-shaped cells are often cost-effective and available in myriad sizes. They also come in a variety of heights ranging from about 4 mm to about 12 mm. The most common size is the 50-mm length and 34-mm width footprint.

    Li-ion prismatic batteries with a thin layered polymer can be housed in a metal can (Fig. 2). Note that the prismatic cell has a pressure vent with the terminals on the metal can. The positive and negative terminals on the polymer cell are tabs protruding from the cell. The typical capacity of a prismatic cell ranges from 1 Ahr to 3 Ahrs.

          
     

    ---

38. Mixology 101: Mixers And Modulators In High-Speed Communications
    
     

    In high-speed wireless communications systems, signals must be translated in frequency by up-conversion or down-conversion for signal propagation and processing. Traditionally known as mixing, this frequency conversion is fundamental to both receive and transmit chains.

    Mixers and modulators, then, are the basic building blocks for radio-frequency (RF) systems. As wireless communications standards continue to evolve, it is essential to review the characteristics of these building blocks and to understand how mixers impact the overall system performance.

    In any radio design, mixers and modulators allow frequency translation and enable communication. They establish the basic specifications for the entire signal chain. And, they see the highest power in the receive chain, up-convert signals from the digital-to-analog converter (DAC) in the transmit path, and enable digital pre-distortion (DPD) systems, impacting the performance of the complete communication system.

    So how does the basic mixer work, which specifications are important to consider, and what options of mixers and modulators are available today to improve and simplify system design?

    
    
    
    
     

    ---

39. Take Time For A Clock-Chip Update
    
    In choosing clock chips for high-performance data converters, the most critical datasheet characteristic is jitter, which translates to phase noise in the frequency domain (Fig. 1). You can look at the jitter as uncertainty in the placement of the data conversion. But from an analytical standpoint, it may be useful to look at that phase noise as a limitation on signal-to-noise ratio (SNR). Really high-performance, high-speed converters require clocks with RMS jitter below 200 fs.
    
    

    ---

40. The ABCs Of ADCs
    
    
     

    ---

41. Rechargeable-Battery Power Management Demands Multiple ICs
    
    
     

    ---

42. Can Home Networking Find A Happy Medium?
    
    
     

    ---

43. Batteries 101: From Nickel To Lithium And Beyond
    
    Virtually all battery-based power-management designs depend on the associated battery, so design starts by picking the specific battery type. The battery may be the non-rechargeable primary type or the rechargeable secondary type. The most widely used rechargeable battery-based systems may employ nickel-cadmium (NiCd), nickel-metal-hydride (NiMH), lithium-ion (Li-ion), or Li-ion polymer, though silver-zinc batteries are now emerging.
     

    ---

44. Modern DSP Chips Serve Up Variations On A Theme
    
    
     

    ---

45. Welcome To Antennas 101
     

    Antennas are much more than simple devices connected to every radio. They’re the transducers that convert the voltage from a transmitter into a radio signal. And they pick radio signals out of the air and convert them into a voltage for recovery in a receiver.

    Typically taken for granted and left for the last minute in a design, antennas are nonetheless critical for establishing and maintaining a reliable radio connection. They may look complex and enigmatic to most engineers, especially EEs working with wireless applications for the first time—not to mention that they come in a seemingly infinite variety of sizes and shapes. However, a brief review of the essentials can help allay any design worries.

    
    
    
    
     

    ---

46. Antennas 102: More Questions And Answers
    
    
     

    ---

47. Without Thermal Analysis, You Might Get Burned
    
    
     

    ---

48. DDS Basics
    
    
     

    ---

49. DDS vs/ Si570 ... Hans Summer, G0UPL ... http://www.hanssummers.com/ddssi570.html
    
    The Si570 is a relatively new device made by Silicon Labs. It's a very small device containing a crystal reference oscillator, digital Phase Locked Loop (PLL), and I2C interface so it can be programmed for any frequency between 10MHz and 945MHz (selected frequencies to 1.4GHz). Direct Digital Synthesis (DDS) chips such as those from the market leader Analog Devices have been around for longer. They are very different kinds of parts, even though they are both oscillators. Accordingly the best choice depends heavily on the application. These are my opinions about the relative advantages and disadvantages which may be important factors for your decision.
    
    

    So after all that [discussion by category], here's my summary of my opinion on the various criteria by which to judge these two kinds of oscillator. Bear in mind that every application is different! In some applications, some of these criteria don't matter to you at all, or the decision of what is better will be clear (and opposite to my conclusion). In others, you are faced with the usual decisions about trade-offs. Performance and complexity; features and cost; etc. But I'll generalise and operate in typically bi-polar manner and give my overall winner in every category regardless, and leave the judging of your applications to you.

    Category	Winner
    Ease of construction	Si570
    Output waveform	DDS
    Frequency range	Si570
    Frequency stability/accuracy	DDS
    Frequency agility	DDS
    Programming interface	DDS
    Performance: Spurs	Si570
    Performance: Phase noise	DDS
    Power Consumption	Si570
    Cost	Si570
    Other features	DDS
    Overall Complexity	Si570

     

    ---

50. Back To Amp Camp  
    
    
     

    ---

51. Temperature Sensors Are Hot In Circuit Design
    
    
     

    ---

52. Stop The Waste In Your Battery-Charger Conversion
    
    
     

    ---

53. Make Your Next Design As Solid As A Rock
    
    
     

    ---

54. Secure That Microcontroller
    
    
     

     

     

    ---

    Cool Product of the Month ... Ultimate2 QRSS Kit, by Hans Summers, G0UPL

     

    The ultimate QRSS Transmitter Kit is a new version of the original Ultimate QRSS kit. This new version comes with a pre-assembled AD9850 DDS module, and plug-in low pass filter modules which are also available separately for any band. The kit can transmit on any frequency from audio (500Hz) to over 40MHz, and changing bands is a matter of plugging in the appropriate low pass filter kit to attenuate unwanted harmonic output.

    
    QRSS ... WSPR ... FSK/CW ... DFCW ... Hellshreiber ... CW ... FSK