This CWTD blog focuses on technology basics and tutorials, equipment reviews, new technology explorations, and construction/analysis of projects that are of keen interest to experimenters in electronics, and anyone interested in Amateur Radio. Our various blog threads provide lots of useful information and photo illustrations of techniques.  Over the years we have developed quite a collection of podcast material -- see the substantive list below.  Going forward we're growing this site with new material and will at times record audio/video segments for here and YouTube.

73, George N2APB

N2APB                                                                                             N2CX (sk)

Note that Joe Everhart N2CX is now SK, but his engineering principles, sensible guidance, and at-times irreverent humor will continue to live on with us here in CWTD. 
Joe had been my Elmer, my best friend and a direct collaborator with me on every ham endeavor for more than two decades. 
He will be fondly remembered in the ham community that he loved so much over the years. .... n2apb

CWTD Project Collections:

GPS-Disciplined Oscillator

Precision Arduino Clock

Design Notebook Series

The PSoC Project

Member Projects

Engineering Course Notes


RSS feed:  cwtd.rss          

"Test Gadgets" and Test Equipment You Can Build
Oct 11, 2018 Whiteboard   91) Audio Test Gadget ... Our topic this time addresses the design and construction of an Audio Test Gadget based on our evolving Test Gadget Design Series.  This new "Audio TG" can serve as a mainstay on your ham workbench for audio testing, evaluation and ongoing experimentation on either your Nano TG motherboard, or the ESP32 TG motherboard. 
Sept 12, 2018 Whiteboard Podcast 90) Measuring Crystals with the SNA Test Gadget -- This episode considers the combination of two test gadgets developed in previous installments into a single measurement system called the Scalar Network Analyzer.  By connecting the Siggen test gadget to the input of a Device Under Test (like a crystal filter), and the output of the D.U.T. to our RF Power Meter test gadget, we have a complete loop that can be used to determine the response characteristic of that crystal filter.  In other words, we squirt some RF into a filter and measure how much of that signal comes out, thus giving us a good feel for how that filter will perform in a given circuit implementation.  Additionally ... We now have prototype pcb's for our two "standardized" Test Gadget platforms:  (1) The Nano Test Gadget, for quick & simple Gadget experimentation; and (2) The ESP32 Test Gadget, for powerful simultaneous control and graphical display for all Gadgets we develop. 
Aug 7, 2018 Whiteboard Podcast 89) A Tale of Three Platforms --   Three controllers have evolved in consideration of being THE controller on our Test Gadget motherboard ... the Arduino Nano, the Teensy, and the ESP32.  Each has strengths and weaknesses, but why not continue to evolve our "GadgetRack" software to be used on each of those three platforms?!  After all, software for each is developed in the standard Arduino IDE (integrated development environment) and common libraries can be shared in each sketch. We have been experimenting along these lines with each platform over the past month and explore this very opportunity (or dilemma) this time.
May 8, 2018 Whiteboard Podcast 88) Power Measurement Test Gadget --   The topic this time is RF Power Measurement, using a new simple plug-in Test Gadget that we're adding to our Arduino base board.  When coupled with the DDS Siggen gadget built last month, we can now squirt some RF into a test circuit (LPF, amplifier, L/C/R network, whatever) and then measure its response, providing some great indicators of that circuit's performance.  This capability forms the basis of a simple scalar network analyzer (SNA) that can be enhanced in any number of ways, as dictated by the needs of your own bench!
Apr 10, 2018 Whiteboard Podcast 87) SigGen Test Gadget --   Signal generators (synthesizers) have been at the very core of every ham's interest and communication mode since the dawn of Amateur Radio.  In this episode we add a "Signal Generator Test Gadget to our line-up of little modules in our Test Equipment You Can Build series. Just plug in this new DDS-60 based module to our standard Arduino baseboard controller, add the simple illustrative sketch (software) to it, and you'll be off to the races!  Also check out the other siggen modules (Si5351 and an offshore AD9851 DDS module), as well as the evolving Gagdet Rack software from AD7JT that controls each of the Gadgets as we continue evolving the platform.
Mar 11, 2018 Whiteboard Podcast 86) Nano Ohmmeter Test Gadget --   What bench is complete without an ohmmeter? In this episode we tackle the basics of measuring resistance without Arduino base board and a new plug-in Test Gadget.
Feb 13, 2018 Whiteboard Podcast 85) Test Equipment That You Can Build -- The Nano Voltmeter Test Gadget --   We started off the 2018 with the theme of "Test Equipment You Can Build" ... Whatever there is to test, we'll be detailing the design of an existing (or original) "Test Gadget" that we flesh out for ourselves.  The emphasis will be on low cost and build-ability.  When parts are needed, we'll be sourcing small runs for those interested in building along with us.  Our episodes will go through the design, build and usage of our "Test Gadget of the Month".  This month's project is the Nano Voltmeter Test Gadget..
Elmer 101:  The "Small Wonder 30 Plus" Blog
Oct 13, 2016 Whiteboard Podcast 84) Elmer 101 Episode #7 (Last) -  Audio Output & Tx Final Amp --   This is IT ... the last in our series of Elmer 101 episodes chronicling the build-up and test of the Small Wonder Labs SW30+ Transceiver!  We'll cover the audio output stage and the Tx final amplifier stage.
Aug 9, 2016 Whiteboard Podcast 83) Elmer 101 Episode #6 -  Rx Product Detector & Audio Preamp" --   We're closing in on the completion of the SW30+ build-up!  This time we take the output of the crystal filter and mix it down to audio baseband in order to get the CW tone we hear in our headphones.  So with this episode we'll start continue studying the Big Picture seen in the diagram "Anatomy of a Homebrew Station", and then "zoom in" on a couple of accessories (DSP audio filter and a simple keyer) as they are being built-up by intrepid homebrewers.  (Also in this episode we started broadcasting a live video feed via the Zoom conferencing tool ... at the same time as using our ever-faithful Teamspeak audio client. Just put your Zoom client on mute and watch the show, as you listen and speak on the show using Teamspeak per usual.  Pretty cool, eh?!)
Jul 26, 2016 Whiteboard Podcast 82) Elmer 101 Episode #5 -  Rx Mixer & Crystal Filter ... and "Anatomy of a Homebrew Station" --   This installment is a pretty cool one where we now start working on the "receive chain" of the SW30 Transceiver. Also as is now customary, we have an interesting "lead-in" topic to the main event, and this time it concerns the "Anatomy of a Homebrew Station". The little Small Wonder rig gives us a terrific start to a larger homebrew station, and as many of us know, there's all sorts of exciting "accessories" that can be added to enhance the value, performance and enjoyment of that station. So with this episode we'll start by looking at the Big Picture and in subsequent episodes we can drill down into the many accessories that one can build just for that purpose. And I do think you'll be impressed by the prodigious panoply of projects!
Jul 12, 2016 Whiteboard Podcast 81) Elmer 101 Episode #4 - Tx BPF, Buffer & Driver --   Are you keeping up with us in building your SW30+ rig?!  In this episode we are finishing off much of the Tx chain and and getting closer to seeing signal squirting out of this little radio!  We also discuss a handful of real interesting New Products that have surfaced recently.
Jun 28, 2016 Whiteboard Podcast 80) Elmer 101 Episode #3 - Keying & Tx Mixer --   In this episode, we'll analyze the Keyer and Transmit Mixer circuits, and discussing its components, testing and operation.  At the end of this "step 4" in the assembly manual, you'll be seeing the first evidence of the 10.1 MHz signal that ultimately gets transmitted!
Jun 14, 2016 Whiteboard Podcast 79) Elmer 101 Episode #2 - VFO --  Last time, we had the official kick-off and overview and everyone now should have their kits and started the assembly process. In this episode, we'll analyze the VFO section, and recap the "build process" up to the STEP 3: VFO Assembly, Measurement and Test.  At the end of this stage, you'll be seeing the first signals emerge from your board!
May 31, 2016 Whiteboard Podcast 78) Elmer 101 Episode #1 - Overview --  Welcome to the kickoff episode of our Elmer 101 series!. In these informative, instructional and interactive sessions we will be chronicling the design, construction and analysis of the famous SW30+ Transceiver by Dave Benson, K1SWL.
In this first episode we cover ...
1) The Elmer 101 approach ... how we'll cover all the great material in many follow-on episodes;
2) Available documents ... many great ones are already available, and we have a killer addition to the pool;
3) CWTD SW30+ Kit Overview ... and a walk-thru of parts inventory;
4) Great accessories ... enclosure, frequency display, keyer;
5) Ordering window open
Dec 22, 2015 Whiteboard Podcast 77) Fun with Portable QRP Antennas --  We've all tossed some wire up into a tree for use as an antenna, purchased a nifty antenna product for field use, or just hung a wire out the window.  N2CX leads us in this episode based on his years of engineering-based, professional and hobby experience with such antennas ... and the joy and value that can be had.  We also provide an update on the two major projects in-progress ...the GPS-Disciplined Oscillator, and the Elmer 101 Course and its companion SW30+ Transceiver Kit.  
Nov 17, 2015 Whiteboard Podcast

76) Analog Dialogue--  We found this really well done reference manual called the "Analog Engineer's Pocket Reference" from Texas Instruments and we just knew that we had to share it with our CWTD audience!  And what better way to do this than in the style of our long-standing "Analyze This!" episodes, whereby we go through the relevant sections in a step-by-step manner, providing parenthetical insight and experience as it relates to all us homebrewers and experimenters.  Additionally, we've been kept the midnight oil burning in the background on our THREE MAJOR EFFORTS here in recent months on CWTD ... The GPS-Disciplined Oscillator project, the Elmer 101 Course and its companion SW30+ Transceiver Kit.   Here in this episode, our CWTD Dev Team brings us all up to speed with various aspects of these projects that will soon be breaking upon the shores of your workbench!

Oct 13, 2015 Whiteboard Podcast

75) GPS Topics--  This is Part 3 in our series of CWTD episodes chronicling the design and build of a GPS-Disciplined Oscillator.  We snug up a number of loops that we loosely tied in the previous two episodes concerning GPS receiver basics, timing and "oscillator disciplining" implications, oven control and temperature display. We also "tear down" the popular NEO-6/7/8 GPS modules available on eBay these days. No longer is it intimidating to experiment with these postage stamp-sized boards and antennas. Taking the mystery out of them and showing how we can use these little gems in the shack is what it's all about. We also touch on some select topics in a popular "GPS Compendium" document from u-blox, a popular manufacturer of little GPS receiver modules. Further, we'll are reporting on some fabulous progress that the design team has been making on the GPS Display Terminal that we excitedly announced last time.

Sep 8, 2015 Whiteboard Podcast

74) Oven Control for the VCXO-- This is Part 2 in our series on the design of a "GPS-Disciplined Oscillator, and this time we focus on a circuit intended to maintain temperature of a Voltage Controlled Crystal Oscillator, and thus help to improve the stability of its output frequency. We'll be doing this by means of a control loop that drives a heating element keeping the local temperature inside the enclosure constant at about 45-degC +/- 1. This latest project installment comes in the form of a small kit (parts + pcb) that also includes temperature hi/lo LEDs, voltage regulators, and a motherboard to hold the whole assembly that slides into a nice extruded aluminum (and insulated!) enclosure. So follow along and learn first-hand how to keep your oscillator's temperature under control, and thereby its frequency stable!

Aug 11, 2015 Whiteboard Podcast

73) Frequency .... Accuracy and Stability for the Ham Shack-- This episode is all about "Frequency", a fundamental element of our lives as hams.  In our typical fashion, we are addressing the topic with techniques, devices and equipment to measure frequency with relatively good accuracy.  Being able to determine its stability.  Various time & frequency projects that are price-achievable and quite usable in the shack.  And "disciplining" approaches to improve performance (such as phase noise).  The nifty project this time is the "CWTD Voltage-Controlled Crystal Oscillator", or VCXO ... a module that will serve as the basis for ultimately producing our very own GPS-Disciplined Oscillator for super stability and accuracy! 

Apr 28, 2015 Whiteboard Podcast 72) Elmer 101 & the SW30 Transceiver-- We kicked off the first string of monthly CWTD programs that focus on “Elmer 101” instruction and guidance as many of us build up the resurrected SW30 superhet transceiver kit originally produced by Small Wonder Labs some time ago. Many great instructional references were published several years ago and we’ll be paralleling portions of each as we ramp up CWTD participants and podcasters on the theory and design of the project, while stage-by-stage building Dave Benson’s K1SWL classic little 30m kit. (A limited run of the SW30 Kit is being done for CWTDers, with permission and assistance from K1SWL.)
Mar 10, 2015 Whiteboard Podcast 71) Scalar Network Analyzers -- Guest designer Dave Collins, AD7JT walks us through the topic of measuring a circuit's behavior to an RF stimulus, and his exciting new homebrew design of a super-useful instrument for doing this called the Scalar Network Analyzer.  The SNA is a handheld instrument with a color graphic display (with a touch screen!) that enables the user to measure performance of things like LPFs, crystals, and receivers, while also serving as a precision RF signal source and an accurate RF power meter!
Jun 17, 2014 Whiteboard Podcast 70) Small Transmitting Loops for Portable Use ... and the AlexLoop  --  Alex PY1AHD, inventor and manufacturer of the immensely popular "AlexLoop" will be joining us for a discussion of Loop antennas for use while portable in the field.  This is a very "practical" episode, where we briefly touch on STL design principles, and even describe a simple version that one can make with a some copper tubing and a capacitor. The highlight of the show will be when Alex PY1AHD tells his stories of how he designed and evolved his version of the loop, appropriately called the AlexLoop.  The painstaking "cut-and-measure" techniques that Alex went through over time has produced an elegant solution for hams looking to take their ham radios along to the vacation house, while walking around on mountaintops, or even while sitting in the sand at a beach!
Jun 3, 2014 Whiteboard Podcast 69) Signal Measurement Techniques  -- "How's my signal, OM?"  This is probably the most often asked question on the ham bands, mainly because most amateurs don't have the instrumentation to measure or otherwise determine how good their transmitted audio or RF signal quality is.  Techniques for determining signal quality range from the simple and seat-of-the-pants types of approaches, to the complex, esoteric and expensive methods that many of us perhaps only dream about being able to perform. In this episode of CWTD we'll explore different aspects of what constitutes "good signal quality" ... and inexpensive ways you might consider being able to determine if you have it!
May 6, 2014 Whiteboard Podcast 68) Automatic Level Control (ALC) Techniques for DDS-based Designs  -- Most homebrewers know that DDS boards suffer from output level roll-off due to the sampling theorem (sinc function), as well as due to gain-product bandwidth limitations of amplifiers used after the LPF on the DDS boards. And sometimes that roll-off can result in as much as five times lower voltage level at 60 MHz than at the lower frequencies. For applications using a DDS in accurate measurement applications, designers usually correct for this frequency-dependent level change using some sort of calibration technique ... which can sometimes be a challenge. In this episode of CWTD, we discuss a relatively simple ALC circuit that seems to be working splendidly, and can be used with any designs using the AD9850 or AD9851 DDS chips. We believe it will have a profound effect on applications performing accurate measurements.
Apr 22, 2014 Whiteboard Podcast 67) Network Analyzer Terminal for the PHSNA  --Test instruments, radios and bench accessories for the electronics experimenter these days are increasingly using the PC to augment the instrument’s control, data processing and display capabilities. Whether for remote operation, remote display or post processing, the PC offers much computational power via the serial port connection to the instrument. However this extension of the instrument’s capabilities comes at a price, considering the size of the PC, the complexity of making the serial connections work, and the updating and configuration of the PC application being used for the enhanced capabilities.  Enter the Network Analyzer Terminal  A handheld graphic display terminal for controlling the Poor Ham's Scalar Network Analyzer ... and more!  
Dec 10, 2013 Whiteboard Podcast 66) Poor Ham's Scalar Network Analyzer (PHSNA)  -- Being the intrepid homebrewers and experimenters that we all are here in CWTD, we are always on the lookout for simple measurement equipment that can be used for giving us greater insight to the radio projects on our benches.  Several months ago N5IB and W5JH teamed up to develop a useful-and-inexpensive way to sweep an RF signal through a Device-Under-Test and read/plot the power coming back from it, yielding insightful characteristics. We wanted to explore some of the background information here with our CWTD members and get some "insider knowledge" from the masterminds behind the project!
Nov 26, 2013 Whiteboard Podcast 65) Troubleshooting Techniques - LIVE!  -- We have a groundbreaking, trail-blazing, state-of-the-art program this time as we attempt to get a 10 MHz variable crystal oscillator (VXO) working ... interactively, in real-time, and viewable in real-time video streams over the Internet!  So in addition to learning some troubleshooting techniques and approaches from the more experienced homebrewers on the program, and being able to ask questions like "why probe here?" or "what does that signal look like?", you be able to SEE the measurements being made! 
Nov 12, 2013 Whiteboard Podcast 64) The Art and Science of Evaluating Electrical Connections  -- So you think you know about making resistance measurements, eh?  Just take the ol' $2.99 "special" VOM you got from Harbor Freight or Best Buy, probe that connection, and voila!  Well, sometimes it's as easy as that, but things can get tricky if you need to measure accurately at the very low end of the range ... say in the milliohm region (i.e., 10 milliohms = 0.010 ohm).  That inexpensive VOM probably won't hack it, and even some DMMs run out of gas down there will not be good enough for use. So our topic this time is making resistance measurements in those hard to reach areas ... And we'll present a couple of simple-yet-effective instruments that you can build:  a milliohmmeter and an audible continuity tester.
Oct 29, 2013 Whiteboard Podcast 63) Making the 2013 Christmas List -- The topic this time is our usual one for this time of the year ... an informal roundtable discussion of all the cool new projects on the market (station accessories, tools, antennas, rigs and gadgets) that we might be interested on putting on the Wish List this holiday season.  Should be fun discussion and maybe you'll find a couple of must-haves for your own stocking hung from the chimney with care come December ... it's never too early to order these things! ;-)
Oct 15, 2013 Whiteboard Podcast 62) Shortwave Listening: A Fireside Chat -- Okay, time to 'fess up: How many of us really enjoy "listening" without the bother (sometimes) of ensuring the transmitter and antenna are tuned, or the worry (sometimes) of getting engaged in a protracted QSO that extends beyond the time we have available in the shack on any given night?  My hand would be the first to go up!   But when this situation is present I often turn on the general coverage receiver to allow me to tune across the shortwave bands looking for an elusive AM station from a faraway land, or a foreign news station with "another perspective", or just some strange and exotic-sounding tunes undulating through the ionosphere. Whatever your reasoning and justification of this shortwave radio playtime, it is indeed fun and educational ... even for technologists and homebrewers like us!  In this episode we will be exploring the history, the commercial and hobbyist-oriented radio gear, the plethora of shortwave stations on the air at any given hour of the day, and the techniques (and even contesting!) that we engage in while SWL'ing.
Oct 1, 2013 Whiteboard   Add-Hoc Session
What happens when schedules collide and the regular hosts aren't around to run the show?   Well, the show goes on anyway! ... Python, Raspberry Pi, Tablets, Android programming and Small Dev Boards
Sept 17, 2013 Whiteboard Podcast 61) Analyze This!  Elecraft 2T-Gen Test Oscillator -- In this episode we overview the basics of two-tone testing, and very quickly get to the Elecraft 2T-gen circuit to break it down and analyze its functions. With actual, documented experience of using it on the bench, we show the benefits of performing the procedures for IMD and PEP measurements to give CWTD members another powerful tool in their arsenal of test equipment for the bench.
Aug 27, 2013 Whiteboard Podcast 60) What's on YOUR Bench?! -- We do something a little different this time ... in fact, something completely opposite! We usually establish a theme, pre-populate the whiteboard with notes and relevant information, and then Joe and I talk through the technology and the "designer experience", and then usually discuss a homebrew project that demonstrates/illustrates the principles of this episode.  But ... In this episode we have all YOU do the talking ... and we chat about all the projects that YOU have on the bench, have completed, or perhaps in greater volume, all those projects that you are planning.
Aug 13, 2013 Whiteboard Podcast 59) Remote Display Node and Power Supply Basics for Hollow State Designs -- In the first half of this episode, we experiment with the battery-powered, jumbo-sized 7-segment, 4-digit LED display array that hangs on the wall to display hours and minutes, as well as 1-of-60 discrete blue and yellow LEDs that tick off the seconds as received from the Arduino base station with an RTC synchronized to WWV.  And in the second half of the episode, we introduce the next project:  A Thermatron Audio Amplifier ... and we start off with the basics of a simple DIY power supply for it.
July 23, 2013 Whiteboard Podcast 58) Exploring the PSoC -- Last time we introduced the PSoC "Programmable System on a Chip", and this time we really got into the inner workings of the chip's capabilities, and more importantly how to use the PSoC Creator to make your first project: an LED Dimmer.  We've selected the freeSoC Mini as our inexpensive little dev platform upon which we'll build up to producing a standalone SDR Receiver for Amateur Radio ... of course not requiring a PC!  We also provided an update on the Arduino Clock Project, and reviewed a fabulous book that is newly available: Hollow State Design", by Grayson Evans KJ7UM and available from Electric Radio.
July 2, 2013 Whiteboard Podcast 57) Experimenting with the Xtrinsic Evaluation Board -- One of our regular CWTD attendees recently pointed us toward this really interesting low-cost evaluation board that is just chock full of interesting sensors.  So while waiting for our own boards to arrive in the mail, we thought that we'd go through the capabilities of this "XTRINSIC" board to help you decide what you might be able to do with it!  Additionally, we introduce the CWTD PSOC Project ... a low cost, Programmable System On a Chip controller that we'll be configuring over a couple of forthcoming episodes to couple with a Softrock RF front end to serve as a standalone receiver.
June 18, 2013 Whiteboard Podcast 56) CWTD Designer Notebook #1 ... Design Essentials -- We recently introduced the CWTD Designer Notebook Series as a collection of useful, informative and "reference-able" resources that DIY ham homebrewers and designers would likely use on a regular basis. We have been maintaining these references over the years, and when one of us finds a good article, reference information, video link -- essentially anything that we find interesting and useful in pursuit of our technology projects on the bench -- we exchange the link and file it into our respective "design notebooks". This episode on Design Notebook #1: Designer Essentials gives the listener a sense of the material that we think is especially interesting and relevant to us these days ... from Arduinos to Op Amps. From Digital Scope Usage to Understanding Noise in Digital Circuits. From Antennas 101 to Impedance Matching. Most of these articles are short, easy to read, and have additional reference links if you are interested in digging deeper.
June 4, 2013 Whiteboard Podcast 55) Analyze This! ... Direct Digital Synthesis (DDS) -- This time we pick up with the popular "Analyze This!" series again with a dissection and analysis of the very popular DDS circuits that serve as Local Oscillators in many of our homebrew projects these days.  While the circuits are relatively small and principles of operation are believed known by most, you might find that some design aspects can surprise you.  Whether it is voltage level translation, parasitic oscillations in the post-LPF amplifier, or high current draw and seemingly excessive package temperatures, this episode of CWTD is likely to give you additional considerations when selecting and using a DDS circuit for your next project.  
May 21, 2013 Whiteboard Podcast 54) Audio in the Ham Shack -- This time we explore another "common denominator" we all share in our ham stations ... audio!  For years we probably haven't paid too much attention to the microphones and speakers we use with our rigs, or the impedances when using devices other than the normal options for a given rig.  But with the plethora of fancy accessories we can get these days, it behooves us to better understand some of the basics so we are not losing half the levels or half the frequency range of the devices and/or radio. 
May 7, 2013 Whiteboard Podcast 53) Component Testing: "A (meter's) got to know his limitations" -- Sure, everyone these days knows what to measure with a DVM or even with one of the fancy, all-in-one component testers like the ubiquitous (and very good) L/C Meter II-B from AADE.  But what do those measurements mean?  What are the circuit implications?  At what frequency does the measurement have significance for you?  And what about the not-so-common measurements that can be all-important to some homebrewers ... like effective series resistance of a capacitor you dig up at the bottom of your boatanchor junk box?  Well, this time we explore these questions, and many other dimensions of measuring resistance, capacitance, inductance, transformers, transistors, ... And perhaps you'll come away from this episode with some new insights for just what components you do have in your junk box!
April 23, 2013 Whiteboard Podcast

52a) Remote 7-segment LED Display for the Precision Arduino Clock -- This installment of the Clock project combines the XBee RF link topic from last time with a 4-digit,7-segment multiplexed LED module to provide remote display of time for the radio shack.
52bTools for the Homebrewer's Workbench and Workshop -- This collection of "essential tools" for the homebrewing workbench will turn you and your projects into a star!  Seriously, they are mostly inexpensive and every good homebrewer should outfit his shop with these basic items.  
52c) Cool Product of the Month --  A new regular segment is added to our bi-weekly program, describing a cool new product for us homebrewers ... this time it's the Si4707 Weather Band and SAME Data Receiver.  Just think of the cool thinks we can do with this little board in out Ham Station Mesh Network ! ;-)

April 9, 2013 Whiteboard Podcast 51) XBee RF Data Link for Ham Station Mesh Networking (Part 1) and Arduino Clock Synchronization & 7-Segment Display
We first start an interesting group project that will lead in several episodes to the creation of a functional, useful and indeed valuable "mesh network" for data and control within our ham stations.  We begin by using a couple of XBee modules to set up a remote terminal modem capability. Then we reconfigure the standalone remote node to read a temperature sensor and send data over the RF link to the XBee receiver on the base Arduino for display in the serial console. 
Our second focus
deals with the addition of a 7-segment, 4-digit multiplexed LED module to provide time and temperature readouts (soon) on our Precision Arduino Clock project.
Mar 26, 2013 Whiteboard Podcast 50) Two topics this time! ... AM Mode and RTC Software for the Precision Arduino Clock Project
We first consider a venerable operating mode that many of Old Timers grew up using: Amplitude Modulation. We take a brief look at the technology and construct of AM operation, as well as how it is implemented in even one of the most modern SDR rigs today: the SDR Cube Transceiver.
Our second focus is on our continuing group project: the Precision Arduino Clock. This time we implement the software for a key element for moving forward: the Real-Time Clock. Surprisingly, the Arduino sketch (software) is vastly simplified and we have the stage set now for making the Arduino and our CWTD shield (hardware) a very useful addition to anyone's shack.
Feb 26, 2013 Whiteboard Podcast 49) Time & Time Again ... Adding a Real-Time Clock Chip to the CWTD Precision Arduino Clock Project
In this week's episode we take our basic “phase 0” Arduino clock and advance the project to the phase 1 milestone with the addition of a Real Time Clock chip (the DS1307). With this hardware addition, our “CWTD Arduino Clock” can be set with accurate time and retain it when power is removed. Then we take a close, step-by-step look at the initial sketch (software) used on the Arduino last time, and show the construct and way that it works. You won’t need to become an expert on sketch design, but it’s always good for a homebrewer to at least have a feel for what makes this project tick.
Feb 5, 2013 Whiteboard Podcast 48) Precision Time Display & Synchronization with the Arduino
Time … you can’t beat it, make it, save it, store it, replay it or out run it.  But we amateurs can measure time using a number of techniques for our benefit in the shack, in our rigs, in our QSOs, and more.  In this session we overview the sometimes-esoteric world of timekeeping and time synchronization available to us (WWV, CHU, GPS, Rubidium, Cesium, etc.) and then spend a good amount of time on a unique Arduino-based project that can grow and be useful to each of us.
Jan 22, 2013 Whiteboard Podcast 47) Arduino Design Tactics
Okay, so who hasn't heard of the Arduino in the last couple of years? It's actually been pretty hard to avoid. But have you given it a try yet for a project on the bench? Perhaps a VFO controller, or maybe a dedicated voltmeter, antenna rotor controller, code practice oscillator ... the list goes on! The Arduino is designed for use by non-techie users: artists to add lights and sound to their works, musicians to add new dimensions to their instruments, hobbyists building robots and R/C vehicles, homeowners to make custom home automation, and tinkerers to make unique alarm systems. The functional modules are simple to use and require only basic electronic and software skills.
Jan 8, 2013 Whiteboard Podcast 46) Analyze This!  Flexible Signal Source
A signal source can be extremely helpful on the homebrewer's bench ... and even more so when "flexible", with a Fractional-N Synthesizer/PLL, programmable gain+attenuation stage, and TFT graphic display.
Dec 11 Whiteboard Podcast 45) Decibels and the Hombrewer
Decibels (dB, dBm, dBW, dBc, dBu) are useful concepts for homebrewing hams to be comfortable with. When these terms come up in magazines and equipment measurement/evaluation articles, we sometimes have trouble focusing on the real issue if we are busy wondering whether 3 dB means a factor of 2 or 4 (or something else). And when it comes to measuring your homebrew creation on the bench, the dB readings become the universal language describing performance: sensitivity, MDS, IMD, gain, LPF rolloff, and more.
Nov 27 Whiteboard Podcast 44) Emergency Preparedness: Before, During and After
In this episode #44 of CWTD, we have noted author and long-time columnist in QRP and ARRL circles: Rich Arland, K7SZ joining with N2APB and N2CX to discuss the equipment, practices and techniques of preparing for emergency communications.  Whether your focus is preparing in the calm warmth of your home, or being directly involved in the disaster relief operations with other hams and response organization, this week’s session of CWTD is bound to be of interest to many.
Nov 13 Whiteboard Podcast 43) RFI Detective
We discuss the topic of finding and eliminating local sources of noise that interfere with signal reception and trying to mitigate them. The basic process is to first try to characterize what the noise characteristics are then to use fairly standard troubleshooting techniques to identify the source(s) and to describe the measures that can be taken to lessen or eliminate the noise. And per usual, we have a great set of references for further study, and a "project" that you can build and use in the shack or around the home to locate troublesome interference.
Oct 16 Whiteboard Podcast 42) Homebrewing VHF/UHF Antennas
We discuss and illustrate examples of getting on the air with 6m, 2m and 70cm (440 MHz).  Most of us know the "mechanics" of HF operation, but VHF and UHF throw some interesting curves at us as far as propagation, feedlines and losses, antenna polarization, power levels, terrestrial impediments, and more.
Oct 2 Whiteboard Podcast 41) Morse Code ... Dying Art or Thriving Specialty?
We explore a bit of the background, overview the various equipment out there for CW operation, and then hunker down on what makes a CW operator tick.  What his tips and tricks are.  If you've never considered using CW mode and Morse code, or if you've let your fist drift away over the years, or even if you are currently active and in the A1 Operator club, we think you'll find the discussion of the "original mode" interesting and eye-opening. 
Sept 18 Whiteboard Podcast 40) Analyze This! ... The Desert Ratt Regenerative Radio Receiver
One of the easiest and best performing receivers to build, the "regen" offers a unique and incomparable operating experience. Once you hear the characteristics whistles and pops when tuning in a station, you'll think of your grandfather's radio in his den while you lay listening to the 1939 Yanks pounding the Philadelphia Athletics. And you'll also hear dynamic range and crystal clarity that is hard to duplicate with others receivers ... even today!!
Sept 11 Whiteboard Podcast 39) Assembling a QRP Station for Field Operation
It's always good to consider what it takes to get a station together for field use.  We'll discuss some things that maybe you hadn't yet considered ... or some important aspects that you should be aware of.
Sept 4 Whiteboard Podcast 38) Analyze This!: The PFR-3A
This time we study the PFR-3A, the KD1JV-designed QRP CW transceiver
Aug 28 Whiteboard Podcast 37) Troubleshooting Techniques, Part 2
Basic guidance on troubleshooting circuits that should be working ... but are not.
Aug 21 Whiteboard Podcast 36) Troubleshooting Techniques, Part 1
Basic guidance on troubleshooting circuits that should be working ... but are not.
Aug 14 Whiteboard Podcast 35) Analyze This!: The 8640-Jr Signal Source
Dissecting and analyzing the 8640-Jr Signal Source
Aug 7 Whiteboard Podcast

34) Toroids ... Selection, Construction and Use
Are you a bit fearful, or at least hesitant, when it comes to dealing with toroids in your homebrew circuits?  If so, this week's episode is made just for you!

Jul 31 Whiteboard Podcast 33) Resistance is Futile
Selecting the correct resistor for RF, DC, audio, power, size, SMT or leaded, package, vendors and more.
Jul 24 Whiteboard Podcast 32) Component Selection
Tips for selecting the right components when you are trying to adapt or modify a project for your own usage.
Jul 17 Whiteboard Podcast 31) Mid-Year Project Recap
Review of the 30 technical topics and 15 projects covered during the first half of this year & status of each!
Jun 26 Whiteboard Podcast 30) GPS Applications in QRP Communications
Using GPS to enhance our communications: digital modes, frequency standards, stability, and more!
Jun 19 Whiteboard Podcast 29) Oscilloscope Applications
Building on the o'scope basics covered earlier in our Apr 10th episode, we now delve into the many productive uses of the 'scope with our projects, with guest host and expert lecturer Alan Wolke W2AEW.
Jun 12 Whiteboard Podcast 28) QRO Power Supplies
Armed with basic principles and components, you can design just the right solution for your needs!
Jun 5 Whiteboard Podcast 27) Retro SWR
Analysis, design and construction of a simple & useful SWR meter from yesteryear!
May 29 Whiteboard Podcast 26) Feedline Frenzy
Which feedline should you use?  How to measure?  Tips & Tricks
May 22 Whiteboard Podcast 25) Antenna Tuners (ATUs)
Impedance matching in a world of mis-matches
May 15 Whiteboard Podcast 24) Remote Control Techniques for Hams
A review of basic principles and "transports" (RF, IR, wired) and an experimenter's platform
May 8 Whiteboard Podcast 23) Homebrewing Techniques
Some ideas for closing the loop on how to get your next new project built up
May 1 Whiteboard Podcast 22) Harmonics & Spurs & Parasitics ("Oh My!")
How to see/measure the various spectra that comes with the generation of the fundamental.
April 24 Whiteboard Podcast 21) Magnetic Loop Design Cookbook
Design guidelines and critical factors for homebrewing an "STL" mag loop ... and a novel example!
Apr 17 Whiteboard Podcast 20) Erecting a Vertical Antenna
Erecting a Vertical Antenna: base, grounding, feedline, tuning, ...
Apr 10 Whiteboard Podcast 19) Oscilloscope Basics
Wondering about how to use an o'scope for your homebrew project?  This session is for you!
Apr 3 Whiteboard Podcast 18) Soldering 101
A guide to the science and art of melting solder
Mar 20 Whiteboard Podcast 17) Simple & Accurate Power Measurement
Homebrew some simple building blocks to extend the range of accurate lab-grade power meters
Mar 13 Whiteboard Podcast 16) Intro to the Digital Modes
Discussion of the many strange-sounding digital mode signals heard on the bands
Mar 6 Whiteboard Podcast

15) Return of the Rainbow Tuner
Multiband end-fed half-wave antenna tuner and multispectral SWR bridge

Feb 28 Whiteboard Podcast 14) Anatomy of a PICAXE SWR Meter
How to control things with a simple, inexpensive BASIC controller
Feb 21 Whiteboard Podcast

13) Circuit Simulation
Spice Up Your Circuits!  A Homebrewer's Overview of Circuit Simulation"

Feb 14 Whiteboard Podcast 12) Schematic Capture and PCB Layout
Tools and techniques used to get a design from the napkin stage to having a pcb on the bench
Jan 31 Whiteboard Podcast 11) Homebrew Battery Chargers
Considerations and cautions in buying, building and using the right kind of chargers.
Jan 24 Whiteboard Podcast 10) Grounding 101
Different approaches, techniques, tool, products and benefits of doing a good job at grounding.
Jan 17 Whiteboard Podcast 9) What is the BEST Antenna?
Discussion of the most common antennas, their relative benefits and drawbacks
Jan 10 Whiteboard Podcast 8) LPF Design mini-tutorial, Part 3
Measuring the filter and comparing to expected results
Jan 3 Whiteboard Podcast 7) LPF Design mini-tutorial, Part 2
Designing the filter, selecting components and building the circuit
Dec 27 Whiteboard Podcast 6) LPF Design mini-tutorial, Part 1
Overview of the Low Pass Filter, specifying the important design goals and parameters
Dec 20 Whiteboard Podcast 5) Best QRP References
The online sites, books, publications, magazines, people, ...
Dec 13 Whiteboard Podcast 4) Favorite Parts & Kit Suppliers
Where do you get your parts from?  Best deals?  Best service?  Best kits?
Dec 6 Whiteboard Podcast 3) Best Kits
What are the best kits on your bench?  Most useful?  Best bang for the buck?
Nov 29 Whiteboard N/A 2) Technology Round Robin
What technology floats your boat?  Microcontroller? PMO or DDS?  SMT or thru-hole?
Nov 22 Whiteboard Podcast 1) RF Power Measurement for QRPers
What techniques, products and parts are around for us homebrewing QRPs to use?


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