Tag Archives: radio hacks

Design & Build Part 2: Multi-Band, Phasing SSB, and SDR

via Hackaday » hardware

 

Amateur radio is the ultimate hacker’s hobby. You can design, build, and put on the air your own high power transceivers. And with this homemade gear you are able to reach out directly, not relying on any infrastructure whatsoever, to connect with people all over the world. It is a thrilling experience to communicate with that long distance station using equipment you created, where you know at that instant what every single transistor is doing as you key down the mic.

In a previous post I described how SSB radio equipment worked and provided an example of a single-band 20m SSB transceiver. In this post I will discuss a multi-band SSB transceiver, an entire homemade amateur station including amplifiers, and conclude with software defined radio (SDR) that you can make in one weekend.

10m and 6m Dual-Band SSB

My second SSB transceiver was dual-band spanning both 6m and 10m wavelengths. I built this radio as part of the ARRL ‘home brew challenge 3′. This followed the same block diagrams as those shown in the previous post except that the two frequency bands of interest spanned one whole octave at 28 MHz and 54 MHz, resulting in additional switching and a wider bandwidth VFO.

Similar fabrication techniques were used, resulting in an old-school appearance.

best image Photos of the dual-band 6m and 10m SSB/CW transceiver. HPIM3019 DSC_0201 Block diagram of the 10m and 6m dual-band SSB/CW transceiver.

Schematics and details are found in the full article in March 2013 QST, and design notes here. The interesting thing about this radio is that its VFO, power amplifier, and front-end cover all HF bands up to the VHF band 2m. This radio could quite easily be made into an all-band radio if the filters were built-out.

An Entire Station!

The most impressive home built station I’ve ever seen was by Mark Mandelkern, K5AM.  Mark published details of all this gear in QEX magazine back in the late 1990s and early 2000s, with schematics, block diagrams, and more are available here.

rack Mark Mandelkern, K5AM, built his entire amateur radio station from scratch. More photos of Mark Mandelkern's station.

In Mark’s Own Words

“All the gear was newly designed and built from scratch. But I was not about to reinvent the superheterodyne. Each project begins with a thorough study of the handbooks and relevant magazine articles. I glean ideas from all previous builders, to whom many thanks are due. Design means selecting and choosing the best ideas which will help produce the intended results. Individual circuits are described in the handbooks; the real design work is to combine them into a complete functioning unit. Getting a whole station built in a finite interval of time meant using mostly tried-and-true methods, and setting to work without trying to invent a new circuit for each stage.”

There’s More

Others who have made their own multi and single-band SSB transceivers:

And others suggest searching on YouTube for on-air demos of some of these radios or post in the comments section.

Phasing SSB and Software Defined Radio

There are other methods to implement SSB equipment, including direct-conversion using phasing (either digital or analog). In this architecture, an I/Q image rejection mixer is used to mix up (for transmit) or down (for receive) to directly modulate or demodulate SSB signals. The back end after the IQ mixer can be implemented with either op-amps or digitization. This is one of the common architectures for early SSB transmitters and today this is the preferred architecture for entry-level software defined radio (SDR) receivers and transmitters.

Photos of a vintage phasing SSB amateur radio equipment. Slicer-recap_zps532b3fdb slb

Software Defined Radio (SDR)

SDR might be a great option for those of you who are more interested in building a kit or writing code instead of building a scratch-built design.  In many cases the software is already written.  And let’s face it, SDR is the future of radio by pushing what was previously analog circuitry into the digital domain, which trades CPU cycles for reductions in analog circuit complexity.

The Soft Rock SDR transceiver kit.
The Soft Rock SDR transceiver kit.

There are many SDR kits available today, including those by AE9RB, the Picastar, or the Heremes.  You can also buy the commercialized version or can mix and match the exciter, PA, and filter boards.  Recently, an SDR was developed using a teensy. Check out hackrf or hackrfblue for the professional to convert to amateur use with the addition of a good power amplifier and some filters.

The best performing software-defined (or DSP) receivers use a hybrid architecture mixing the best practices of analog design with an SDR back-end (sometimes known as a ‘roofing filter‘).  This provides the high-dynamic range architecture of an analog radio with the flexibility of a software defined radio.  This is why the Elecraft K3 is a top performing radio (it is also available as a kit).

Build It

The only way to get started is to build something. Start small, check out the QRP community, try making a single-conversion receiver, try an entry-level SDR, and finally move up to something with a crystal IF filter. Borrow and scale circuits from books such as these:

Or leverage complete ICs and modules like those from Mini-Circuits. There is nothing like making that first long distance contact on radio gear you created from scratch.


Acknowledgement

My cousin, Juliet Hurley, MBA, MSF, MAC for type editing this post.

Author Bio
Gregory L. Charvat only operates radio equipment he builds from scratch, is the author of Small and Short-Range Radar Systems, co-founder of Hyperfine Research Inc., Butterfly Network Inc. (both of which are 4catalyzer companies), visiting research scientist at Camera Culture Group Massachusetts Institute of Technology Media Lab, editor of the Gregory L. Charvat Series on Practical Approaches to Electrical Engineering, and guest commentator on CNN, CBS, Sky News, and others. He was a technical staff member at MIT Lincoln Laboratory where his work on through-wall radar won best paper at the 2010 MSS Tri-Services Radar Symposium and is an MIT Office of the Provost 2011 research highlight. He has taught short radar courses at MIT where his Build a Small Radar course was the top-ranked MIT professional education course in 2011 and has become widely adopted by other universities, laboratories, and private organizations. Starting at an Early Age, Greg developed numerous radar systems, rail SAR imaging sensors, phased-array radar systems; holds several patents; and has developed many other sensors and radio and audio equipment. He has authored numerous publications and has received press for his work. Greg earned a Ph.D in electrical engineering in 2007, an MSEE in 2003, and a BSEE in 2002 from Michigan State University, and is a senior member of the IEEE where he serves on the steering committee for the 2010, 2013, and 2016 IEEE International Symposium on Phased Array Systems and Technology and chaired the IEEE AP-S Boston Chapter from 2010-2011.


Filed under: hardware, how-to, news, radio hacks

Using The Red Pitaya As An SDR

via Hackaday » hardware

The Red Pitaya is a credit-card sized board that runs Linux, has Ethernet, and a good bit of RAM. This sounds a lot like a Raspberry Pi and BeagleBone Black, but the similarities end there. The Red Pitaya also has two RF inputs, two RF outputs, and a load of digital IOs, all connected to an Xilinx SoC that includes an FPGA. [Pavel] realized the Pitaya had all the components of a software-defined radio, and built an implementation to prove it.

The input for the SDR taps directly into one of the high impedance inputs with a simple loop antenna made out of telephone cable. The actual software-defined part of this radio borrows heavily from an Xilinx application note, while everything is controlled by either SDR# or HDSDR.

[Pavel] included a pre-built SD card image with all his software, so cloning this project is simply a matter of copying an SD card and building an antenna. The full source is also available, interesting if you would like to muck about with FPGAs and SDRs.


Filed under: FPGA, hardware, radio hacks

Extrinsic Motivation: BASIC For Bluetooth

via Hackaday » » hardware

BASIC

There’s a lot more to those fancy radio modules you use with your Arduino projects than meets the eye. Many of them are systems on a chip, complete with their own microcontroller and memory that can control your entire blinking LEDs project. Developing for these radio modules is a bit of a challenge, as the IDEs and compilers cost several thousand dollars. [Tim]‘s entry for the Hackaday Prize looks at one of these Bluetooth LE modules – Texas Instrument’s CC2540 and CC2541 – and puts an embedded BASIC interpreter right on the chip.

[Tim]‘s inspiration for this project came from looking at a few popular devices using the CC254X chip. Many of these included a microcontroller and the added costs, complexity, and power requirements that come along with an additional chip. This radio module could easily run any code an ATMega could, and adding another chip to a product seemed like a terrible waste, and certainly not in the spirit of open hardware and software.

The alternative is writing an interpreter for the CC254X chip. He’s chosen BASIC, but added a little bit of Arduino language syntax to make it even easier to develop on. Having already run through a few successful tests involving SPI, I2C and 1-wire devices, [Tim] has a basic system working, but [Tim] admits it does need a little rework to make it easier to use.

It’s a great project, and personally astonishing that it didn’t make the quarterfinal selection for The Hackaday Prize. [Tim] is still working on his project, though, in a great example of extrinsic motivation; he doesn’t need a trip to space to convince him to build something cool.

You can check out [Tim]‘s two minute concept video below.


SpaceWrencherThis project is an official entry to The Hackaday Prize that sadly didn’t make the quarterfinal selection. It’s still a great project, and worthy of a Hackaday post on its own.


Filed under: hardware, radio hacks, The Hackaday Prize

Weightless, the Internet of Things Chip, Becomes Less Vaporware

via Hack a Day» hardware

weightless

Several months ago, we caught wind of Weightless, a $2 chip that will run for 10 years on a AA battery and communicate to a Weightless base station 10 Km away. Yes, this is the fabled Internet of Things chip that will allow sensors of every type to communicate with servers around the world. It looks like Weightless is becoming less and less vaporware, as evidenced by the Weightless SIG hardware roadmap; Weightless modules might be in the hands of makers and designers in just a few short months.

Weightless is an extremely low-cost wireless module that operates in the radio spectrum previously occupied by analog broadcast television. This is a great place for the Internet of Things, as signals in this spectrum have a lot of range and the ability to go through walls. These signals are sent to a Weightless base station where they are then sent over the Internet to servers around the world.

The Weightless SIG has been hard at work producing new silicon, with the third generation of chips heading for volume production next month. The only thing this chip requires is a battery and an antenna, making Weightless integration for new designs and projects a snap.

There’s one thing Weightless is not, and that’s a free, high-speed connection to the Internet with a $2 adapter. Weightless is designed for sensors that only transmit a kilobyte or so a day – medical sensors, irrigation control, and other relatively boring things. There’s a summary video from the recent 2013 Weightless SIG Summit going over all this information below.


Filed under: hardware, radio hacks

An atmega328-based radioteletype XY scope display

via Hack a Day» hardware

[Jack] tipped us about a Crossed Bananas Display (CBD) he just designed. A CBD is a tuning aid for frequency-shift keyed (FSK) modes and is basically an oscilloscope in X-Y mode. At one time, radioteletype operators used binary FSK to transmit text over radio waves. In this scheme, the “1″ is called the mark frequency and the “0″ is called the space frequency. If both frequencies were perfectly tuned (correct phase) the resulting display would look like the one shown above, explaining the origin of the “crossed banana” name.

The build is based on an ATmega328 and a 1.8″ ST7735R display which has a 128×160 resolution. The MC33204PG operational amplifier is used in conjunction with a potentiometer to scale the input in the microcontroller ADC’s range. Another potentiometer sets the refresh rate of the graph. The whole project is enclosed in a painted cast-aluminium bud box and all the sources for this project can be found here.


Filed under: hardware, radio hacks

Adding shoulder buttons to an RC transmitter

via Hack a Day» hardware

radio

[Gerard] does puppeteering and animatronics work, and to remotely control his creations and characters he uses an off-the-shelf remote control radio. It’s you basic 6-channel setup, but [Gerard] wanted a way to control eye blinks and other simple actions with the press of a button. Sure, he could use the toggle switches on his transmitter, but he wanted something that wouldn’t require turning a servo on and off again. To fix this problem, [Gerard] added shoulder buttons to his transmitter with only a little bit of soldering.

[Gerard]‘s transmitter uses toggle switches to send a signal on channels five and six. To add his push buttons, he simply drilled a hole in the plastic enclosure, installed a pair of push buttons, and wired them in parallel to the toggle switches.

Now [Gerard] has momentary switches on channels five and six, perfect for making his creations blink. Since the buttons are wired in parallel with the switches, flicking the switches to the ‘on’ position in effect takes the button out of the circuit, just in case the transmitter gets jostled around.


Filed under: hardware, radio hacks

Open source software defined radio transceiver

via Hack a Day» hardware

SDR

As the year draws to a close, we must look back and look at the advances in amateur radio this year. The RTL-SDR tuner hack, a USB TV Tuner to create a software defined radio receiver, is one of the greatest hacks of the last 12 months and a great justification for 2012 being the year of software defined radio receivers. 2013 is shaping up to have even more advances in the state of software defined radio. This time we’ll be transmitting as well, possibly with [AE9RB]‘s Peaberry SDR transceiver.

The Peaberry SDR transceiver is a kit to both transmit and receive on every HAM band between 160 meters (1.8 MHz) to 17 meters (18 MHz). It does this through a USB interface and a 48kHz, 24-bit interface that is (or will shortly be) compatible with all the major SDR interfaces.

While the Peaberry SDR requires an amateur radio license to operate, we can’t wait to see what else will be coming to the software defined radio scene in the next year.

Thanks [Zach] for sending this one in.


Filed under: hardware, radio hacks