Hams Talk Digital

September 6, 2015 by Al Williams 45 Comments

Morse code qualifies as a digital mode, although organic brains are somewhat better at copying it than electronic ones. Ham radio operators that did “phone” (ham-talk for voice) started out with AM modulation. Sometime after World War II, there was widespread adoption of single side band or SSB. SSB takes up less bandwidth and is more reliable than AM modulation. On the digital side, hams turned to different and more sophisticated digital transmission types with computers pushing bandwidth down and reliability up. However, a recent trend has been to encode voice over ham radio–sort of VoIP with radio instead of Ethernet–using an open source program called freedv.

[AA6E] made a very informative video where he carries on a QSO (a conversation) with a distant station using freedv. What makes it interesting, is towards the end when the two stations switch to regular SSB. The difference is dramatic and really points out how even with less bandwidth (roughly 3 kHz for SSB vs 1.25 kHz), the digital mode is superior. The freedv software (available for Windows or Linux) compresses audio to 700-1600 bits per second and spreads it over 16 QPSK signals.

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Slimline USB Charger For Tiny Ham Radios

September 5, 2015 by Dan Maloney 12 Comments

The recent trend to smaller and smaller handy talkie (HT) transceivers is approaching the limits of the human interface. Sure, engineers could probably continue shrinking the Baofeng and Wouxun HTs further, but pretty soon they’ll just be too small to operate. And it’s getting to the point where the accessories, particularly the battery charging trays, are getting bulkier than the radios. With that in mind, [Mads Hobye] decided to slim down his backpacking loadout by designing a slimline USB charger for his Baofeng HT.

Lacking an external charging jack but sporting a 3.7 volt battery pack with exposed charging terminals on the rear, [Mads] cleverly capitalized on the belt clip to apply spring tension to a laser-cut acrylic plate. A pair of bolts makes contact with the charging terminals on the battery pack, and the attached USB cable allows him to connect to an off-the-shelf 3.7 volt LiPo USB charger, easy to come by in multicopter circles. YMMV – the Baofeng UV-5R dual-band HT sitting on my desk has a 7.4 volt battery pack, so I’d have to make some adjustments. But you have to applaud the simplicity of the build and its packability relative to the OEM charging setup.

This isn’t the first time we’ve seen [Mads] on Hackaday. He and the FabLab RUC crew were recently featured with their open-source robotic arm.

Hacklet 69 – Morse Code Projects

August 7, 2015 by Adam Fabio 10 Comments

With over 160 years of history under its belt, Morse code is by far the oldest digital signaling system known to man. Originally developed for telegraph systems, [Samuel Morse’s] code has been sent over wires, via radio, and even with flashes of light. Hackers, makers and engineers have been working with Morse code throughout history. For many years, simple code keys and practice oscillators were the “hello world” of hobby electronics. In fact, a company which started out selling a Morse key has gone on to become one of the largest electronic component distributors in the world. The company still bears the name of that project: Digi-Key. This week’s Hacklet is all about some of the best Morse code projects on Hackaday.io!

We start with [voxnulla] and Morse key HID + ugly hack. [voxnulla] found an old key at his favorite thrift store. It was dusty, greasy, and for some reason had been painted hospital green. Once the paint and grime were removed, and the original wooden plate restored, the key actually looked pretty good. [Voxnulla] then decided to turn it into a USB Human Interface Device (HID), emulating the keyboard of his computer. An Arduino converts Morse code characters tapped at the key into keystrokes over USB. As [voxnulla] knows, when butterflies aren’t available, real programmers drive vim with a Morse key!

Next up is [Voja Antonic] with Daddy, I don’t have the key. If you didn’t read [Voja’s] article about Hacking the Digital and Social System, check it out! Many apartments have an intercom system where you have to “buzz” someone in, activating a solenoid lock in the door. [Voja] inserted a Microchip PIC12 series microcontroller between the speaker and the unlock button. All a user has to do is tap out the right Morse code password on the call button in the lobby. If the code is accepted, the PIC unlocks the door, and you’re in!

[kodera2t] took things into the digital age with Stand-alone Tiny Morse code encoder/decoder. This project grew out of his general purpose Portable tiny IoT device project. [kodera2t] rolled his own Arduino-compatible board for this project. The tiny ATmega1284 powered computer allows him to encode and decode Morse code. A smartphone-sized keyboard and a lilliputian OLED display serve as the user interface, while rotary encoder allows for variable code speed. You can even “tap” Morse out on one of the tactile buttons!

Finally, we have [Yannick (Gigawipf)] with Portable (morsing) 100W led flashlight. 100 watt LEDs have gotten quite cheap these days, and they’re perfect when you absolutely, positively have to blind everyone around you. These LEDs can also be switched on and off quickly, which makes them perfect for Morse code. In years past, mechanical shutters had to be used to perform the same feat. [Yannick] used a 5000mAh 5S Zippy Li-Po to supply electrons to this hungry beast, while a 600 Watt constant current boost converter keeps that power under control. An Arduino running Morse code converter software controls the boost convert and LED. [Yannick] uses his computer to send a message over the Arduino’s serial link, and the light does the rest, flashing out the message for all to see.

If you want more Morse goodness, check out our brand new Morse code project list! My Morse is a bit rusty, so if I wasn’t able to copy your transmission and missed your project, don’t hesitate to drop me a message on Hackaday.io. That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

$40 Antenna Analyzer With Arduino And AD9850

August 6, 2015 by Al Williams 39 Comments

If you are a hacker, you might consider ham radio operators as innovative. Most people, however, just see them as cheap. So it is no surprise that hams like [jmharvey] will build an antenna analyzer from a DDS module and an Arduino instead of dropping a few hundred dollars on a commercial unit. As he points out, you probably only need an analyzer for a day or two while you set up an antenna. Unless you are a big time antenna builder, the unit will then sit idle on the shelf (or will wind up on loan to hams even cheaper than you are).

The design is rooted in another proven design, but changed to take advantage of parts he happened to have on hand. Although the build is on a universal circuit board, [jmharvey] used Eagle to lay out the circuit as though it were a PCB. Since placement can be important with an RF circuit, this isn’t a bad idea. It’s always easier to move stuff around on the screen than on the perf board.

Since this is a no frills, unit, you are expected to grab the output from the Arduino and manually put it in a spreadsheet to plot the results. There is another version of the Arduino code that drives an OLED screen, although you still need a PC to kick the process off. One interesting feature of the Arduino code is how it deals with the nonlinear nature of the diodes used in the circuit. After plotting the values with known loads, [jmharvey] broke the diode operation into three regions and used different equations for each region. Even so, he warns that readings higher than 1:1 VSWR are only accurate to 10% or 20% – still good enough for ham shack use.

If you want an antenna analyzer for $40 (or less, if you have a good stock of parts) this looks like a worthwhile project. If, however, you want to repurpose it to Rickroll your neighbor’s AM radio, you might want to go with the commercial unit.

Click past the break to see the analyzer in action.

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Visualizing RF Standing Waves

August 6, 2015 by Dan Maloney 14 Comments

Standing waves are one of those topics that lots of people have a working knowledge of, but few seem to really grasp. A Ham radio operator will tell you all about the standing wave ratio (SWR) of his antenna, and he may even have a meter in the shack to measure it. He’ll know that a 1.1 to 1 SWR is a good thing, but 2 to 1 is not so good. Ask him to explain exactly what a standing wave is, though, and chances are good that hands will be waved. But [Allen], a Ham also known as [W2AEW], has just released an excellent video explaining standing waves by measuring signals along an open transmission line.

To really understand standing waves, you’ve got to remember two things. First, waves of any kind will tend to be at least partially reflected when they experience a change in the impedance of the transmission medium. The classic example is an open circuit or short at the end of an RF transmission line, which will perfectly reflect an incoming RF signal back to its source. Second, waves that travel in the same medium overlap each other and their peaks and troughs can be summed. If two waves peak together, they reinforce each other; if a peak and a trough line up, they cancel each other out.

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HamShield Puts Your Arduino On The Radio

July 13, 2015 by Bryan Cockfield 43 Comments

Anybody can grab a USB TV tuner card and start monitoring the airwaves, but to get into the real meat of radio you’ll need your amateur radio license. Once you have that, the bandwidth really opens up… if you can afford the equipment. However, [spaceneedle] and friends have dramatically lowered the costs while increasing the possibilities of owning a radio by creating this ham radio shield for the Arduino.

The HamShield, is a versatile shield for any standard Arduino that allows it to function like an off-the-shelf radio would, but with a virtually unlimited number of functions. Anything that could be imagined can be programmed into the Arduino for use over the air, including voice and packet applications. The project’s sandbox already includes things like setting up mesh networks, communicating over APRS, setting up repeaters or beacons, monitoring weather stations, and a whole host of other ham radio applications.

HamShield operates on a wide range of frequencies and only uses a 250 mW amplifier. The power draw is small enough that the HamShield team operated it from a small solar panel, making it ideal for people in remote areas. The project is currently gathering funding and has surpassed their goal on Kickstarter, branding itself appropriately as the swiss army of amateur radio. The transceiver seems to be very robust, meaning that the only thing standing in the way of using this tool is simply writing the Arduino code for whatever project you want to do, whether that’s as a police scanner or even just a frequency counter. And if you want to follow along on hackaday.io, the project can be found here.

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Pico Space Balloon Circumnavigates The Globe, Twice

July 5, 2015 by Elliot Williams 13 Comments

We’ve reported on “space” balloons before. Heck, some of us have even launched a few. Usually they go way up in the air, take some cool pictures, and land within driving (and retrieving) distance the same afternoon. You get often amazing photos and bragging rights that you took them for the low, low price of a really big helium balloon and a fill.

But what if you shrunk everything down? Over the last few years, [Andy, VK3YT] has been launching ever smaller and lighter balloons with very low power ham radio payloads. So no camera and no photos, but the payback is that he’s launching payloads that weigh around thirteen grams complete with GPS, radio, solar cell, and batteries. They can stay up for weeks and go really far. We’d love to see some construction details beyond the minimalistic “Solar powered party balloon, 25mW TX”. But that about sums it up.

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