From my Twitter feed: diode ring mixers, TAPR news, SDR SA

Stefano_NVR's avatarDr. NVR @Stefano_NVR
How a Diode Ring Mixer works | Mixer operation theory and measurement:


ke9v's avatarJeff Davis
Summer 2014 TAPR PSR Journal Available –> #hamradio


EDNcom's @EDNcom
RT @measurementblue: Michael Dunn tries The $11 spectrum analyzer & SDR @EDNcom @EDNMichael


rtlsdrblog's @rtlsdrblog
BeagleBone Black Image File with RTL-SDR + GNU Radio + More…

On the Internet: W2AEW videos, Raspberry Pi programming, classic radio

Here are a couple of Internet resources to start off the week:

W2AEW on YouTube. Alan, W2AEW, has a great selection of cool videos on YouTube. Some of the latest cover the basics of phase-locked loops, how to zero-beat WWV to check out a frequency counter’s accuracy, and a tutorial on resonant circuits. Good stuff!

Baking Pi – Operating Systems Development. This course, published by the University of Cambridge Computer laboratory, is a free online course that takes you through the basics of operating system development. The Web page notes, “[This course]  is aimed at people aged 16 and upwards, although younger readers may still find some of it accessible, particularly with assistance….I have tried not to assume any prior knowledge of operating systems development or assembly code. It may be helpful to have some programming experience, but the course should be accessible without.”

Classic Exchange. Mac, WQ8U, wrote to the Glowbugs mailing list, “The Classic Exchange (CX) is a low-key, on-air celebration of rigs of days gone by – particularly boat anchors. The latest CX Newsletter is available on the CX web site, as well as details for the next CX on September 16th (for AM and SSB) and September 23nd (for CW). Please enjoy the newsletter, spread the word and join in the fun during the next CX.”

Hack a Day: Use an Arduino to Measure Inductance

It’s been over a year since I built an Arduino microcontroller at our club’s annual construction night, and I still haven’t done anything with it. I’ve had a couple of ideas, including a keyer that would actuate accept paddle inputs and actuate a solenoid that would open and close a straight key, but just haven’t had the time or inclination to actually put something together.

Well, here’s a cool idea as to how to use an Arduino to measure inductance.

Measure inductance with an ArduinoA signal in from the Arduino excites an LC circuit. The L in the LC circuit is our unknown inductor. The output of the LM339 is a square wave whose frequency is proportional to the L of the LC circuit. Measure that frequency with the Arduino and you know the unknown inductance. Of course, calibrating this thing could be a bit tricky, but it might be fun to play with.

Choose the Right Microcontroller

The latest issue of the e-mail newsletter electronic design update is devoted to microcontrollers. It includes the following articles:

The article on whether it’s better to use a microcontroller or a 555 for timing is an interesting one. Microcontrollers have truly gotten so cheap as to make this a real consideration.


More on Microcontrollers

Despite the low price of the TI Launchpad, most of the AMRAD folks thought that this was hardly an Arduino killer. They pointed to all the users and support that the Arduino has.

One cool thing that someone pointed out is the Processing language. This looks like a very cool thing that I’ll have to play around with. According to their website:

Processing is an open source programming language and environment for people who want to create images, animations, and interactions. Initially developed to serve as a software sketchbook and to teach fundamentals of computer programming within a visual context, Processing also has evolved into a tool for generating finished professional work. Today, tens of thousands of students, artists, designers, researchers, and hobbyists who use Processing for learning, prototyping, and production.

One of the projects they pointed to is the “Poorman’s Oscilloscope.” This project uses an Arduino as the analog front end and Processing as the display back end. I think that with a little thought and programming you could also create a simple spectrum analyzer and make your own waterfall display. (I’m thinking that I could perhaps write a Mac version of Argo with Processing.)

TI Makes a Run At Arduino

TI LaunchpadOn the AMRAD Tacos mailing list, Andre, N4ICK writes, “Who couldn’t use one of these?” One of these happens to be the Texas Instruments’ Launchpad, a development platform for their low-cost line of microcontrollers. The kicker is that they’re selling this puppy for only $4.30.

According to the Hack a Day blog post:

Each Launchpad device comes with a whole lot of goodness. In addition to the board itself you get a 0.5 meter USB cable, two pin headers and two pin sockets for the pin breakout pads, two different MSP430 microprocessors (MSP430G2211 and MSP430G2231), and two free IDEs; Code Composer Studio 4 and IAR Embedded Workbench Kickstart (note that the latter has a 4K or 8K code limitation depending on the processor used).

Sounds pretty cool to me.