Licence-Exempt Network Has High Ambitions

March 20, 2016 by Jenny List 18 Comments

It’s safe to say that the Internet of Things is high on the list of buzzwords du jour. It was last seen rapidly ascending towards the Peak of Inflated Expectations on the Gartner Hype Cycle, and it seems that every startup you encounter these days is trying to place an IoT spin on their offering. Behind all the hype though lie some interesting wireless technologies for cheaply making very small microprocessors talk to each other and to the wider world.

Today we’d like to draw your attention to another wireless technology that might be of interest to Hackaday readers working in this area. UKHASnet is a wireless network developed from within the UK high-altitude ballooning community that uses cheap licence-exempt 868MHz radio modules in Europe and 915MHz in the Americas. The modules they are using have a surprisingly usable power output for licence exempt kit at 100mW, so the system has been designed for extensibility and bridging through nodes mounted on balloons, multirotors, or even seaborne buoys.

All UKHASnet packets are sent as human-readable plaintext ASCII, and the system borrows some of the features of amateur radio’s APRS. All packets are considered unreliable, all nodes repeat the packets they receive with their own node ID appended, and there are gateway nodes that make the packets available to the internet. There is a repeat number built into each packet to stop packets continuing ad infinitum.

Building a node is a simple process, requiring only the radio module, a microcontroller, and a battery. As examples they provide an implementation for the Arduino, and one for the LPC810 microcontroller. Their preferred radio module is the HopeRF RFM69HW, however the system will be capable of running on other modules of the same type.

So far the UKHASnet people have proven the system over a 65km range, created nodes on the sea, attached it to quadcopters, and built a host of other nodes.

This network differs from its commercial counterparts in that it has no proprietary IP or licencing from a standards body. And despite the name, you don’t have to be in the UK to use it. All data is in the clear, and thus it is likely that you won’t see it in mass-market commercial products. But it is exactly these features that are likely to make it attractive to the maker community. Your scribe will probably not be the only person who goes away from this article to suggest that their local hackspace finds the space for a UKHASnet node.

This is the first time we’ve featured UKHASnet here at Hackaday. Plenty of projects using licence-free radio modules have made it onto these pages, though, including this extreme-range remote controller for model aircraft, and this weather station sensor network that could have probably found UKHASnet useful had its creator had it to hand.

Rubber Tanks And Sonic Trucks: The Ghost Army Of World War II

December 16, 2015 by Adam Fabio 43 Comments

Winston Churchill once told Joseph Stalin “In wartime, truth is so precious that she should always be attended by a bodyguard of lies”. During World War II, the power of these bodyguards, in the form of military deception, became strikingly apparent. The German military was the most technologically advanced force ever encountered. The Germans were the first to use jet-powered aircraft on the battlefield. They created the enigma machine, which proved to be an extremely difficult system to break. How could the Allies possibly fool them? The answer was a mix of technology and some incredibly talented soldiers.

The men were the 23rd Headquarters Special Troops, better known as the Ghost Army. This unit was the first of its kind specifically created to deceive the enemy. Through multiple operations, they did exactly that. These 1100 soldiers created a diversion that drew German attention and gunfire to them, instead of the thousands of Allied troops they were impersonating.

The Ghost Army consisted of 4 distinct groups:

The 406th Engineer Combat Company Special were 166 “regular” soldiers – these men handled security, construction, and demolition.

603rd Camouflage Engineers were the largest group at 379. As the name implies, the 603rd was created to engineer camouflage.

3132 Signal Service Company consisted of 145 men in charge of half-tracks loaded down with massive 500 watt speakers which could be heard for 15 miles.

The Signal Company Special Formerly the 244th signal company, The 296 men of the Signal Company Special handled spoof radio communications. The Germans heavily relied on captured and decoded radio messages to determine the Allies’ next move.

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Low Parts Count ARM SDR

November 14, 2015 by Al Williams 4 Comments

[Alberto di Bene] wanted to build an SDR for relatively low frequencies. Usually, you’d start with some front end to get the radio frequency signal down where you can work with it. But [Alberto] practically just fed an antenna into an STM32F429 Discovery board and did all the radio processing in the onboard ARM chip.

There is a little more to it than that, but only a little. If you open the PDF file on [Alberto’s] site, you’ll see there is a simple front end filter (a transformer, along with a few capacitors and inductors). This low pass filter prevents high frequencies from reaching the ARM processor’s analog to digital converter. In addition, a capacitor and a couple of resistors ensure the converter only sees positive voltages.

The CPU digitizes the incoming signal and processes it, demodulating several different types of radio transmission. The recovered audio is sent through the onboard digital to analog converter.

In addition to an input filter, the output also needs a filter to prevent high frequencies from reaching the speaker. Unlike the input filter, this one is a bit more complicated. The inductors needed for a passive filter were too large to be practical, so the output filter is an active one with a few transistors. The only other external circuitry is the power supply for the Discovery board.

The document does a great job of explaining the rationale behind the design choices and how the whole system works. It also includes simulations of both analog and digital filters used in the design.

This is really bare metal SDR and reading the code is educational. However, if you want to start with something simpler, consider GNU Radio and either an SDRPlay or a cheap RTL-SDR dongle.

Your First GNU Radio Receiver With SDRPlay

November 12, 2015 by Al Williams 25 Comments

Although GRC (the GNU Radio Companion) uses the word radio, it is really a graphical tool for building DSP applications. In the last post, I showed you how you could experiment with it just by using a sound card (or even less). However, who can resist the lure of building an actual radio by dragging blocks around on a computer screen?

For this post and the accompanying video, I used an SDRPlay. This little black box has an antenna jack on one end and a USB port on the other. You can ask it to give you data about a certain area of the RF spectrum and it will send complex (IQ) data out in a form that GRC (or other DSP tools) can process.

The SDRPlay is a great deal (about $150) but if you don’t want to invest in one there are other options. Some are about the same price (like the HackRF or AirSpy) and have different features. However, you can also use cheap TV dongles, with some limitations. The repurposed dongles are not as sensitive and won’t work at lower frequencies without some external help. On the other hand, they are dirt cheap, so you can overlook a few little wrinkles. You just can’t expect the performance you’ll get out of a more expensive SDR box. Some people add amplifiers and converters to overcome these problems, but at some point it would be more cost effective to just spring for a more expensive converter.

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3D Printed Camera Battery Emulator

January 21, 2015 by Rich Bremer 30 Comments

There are certainly battery hungry devices out there on the market and, unless you do some serious research before the purchase of said device, you really don’t know how it will perform. Needless to say, some of us get stuck with power hog device, and it seriously sucks because changing out batteries often is expensive and just plain annoying.

If you couldn’t tell, I am speaking from experience, my old Sony DSC-H5 camera works great with the exception of needing new batteries every hour. And if you get cheap batteries, the camera won’t even turn on! There’s a USB connector on the camera but it is only for transferring data and there is also no DC input jack. The entire situation is a totally bummer.

I’m happy (or disappointed) that I am not alone in the world. [Phil] wrote into the HaD tip line to tell us about his solution to this very problem. He has a Canon SD1000 camera and although the battery works fine he needs it to work at an altitude of 15km in order to take some sunrise photos. Cold weather testing (in the fridge freezer) showed that the battery isn’t going to cut the mustard for the hour-long flight. The rest of the balloon-lifted unit already has a battery pack and the plan would be to tap into that to power the camera. Unfortunately his camera, like mine, doesn’t have a DC input jack and can not be powered off the USB port.

[Phil] decided to make a 3D printed battery emulator. It sits in place of the stock battery and holds bare wire where the batteries terminals normally are. The other end of the wires are run out of the camera to a voltage regulator that converts the battery pack’s 6 volts down to the 3.9 that the camera needs.

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Hacking An Escape From East Germany

February 2, 2014 by Kristina Panos 39 Comments

Some hacks are just for fun. Some make your job or your life easier. Once in a great while, a hack will save your family from an oppressive government. This is the kind of hack that [Günter] pulled off when he and [Peter] built a homemade hot air balloon to escape East Germany and the oppression of the Stasi in 1979.

Like many East Germans who weren’t in line with the Party, [Günter] found life unsatisfactory on his side of the Berlin Wall. Travel, job options, and freedom of expression were all severely limited. Aside from joining the Communist Party, the only option seemed to be escape to West Germany.

[Günter] and his wife [Petra] were inspired when [Petra]’s sister, who had escaped in 1958, came to visit. She brought with her a newspaper that covered the International Balloon Fiesta in Albuquerque, New Mexico. [Günter] and [Peter], whom he worked with, decided that they would conspire to build a hot air balloon capable of transporting them, their wives, and their four children across the border.

Theirs is an incredible story fraught with adversity. They ended up constructing three different balloons, all the while traveling further and further from home to avoid suspicion when buying large quantities of fabric. They had a lot of trouble finding the right propulsion method and ended up using pure oxygen. During the narrow window they had before [Günter] was due to report for military duty, the weather was unfavorable except for a short period after a front had passed through. They had no time for testing and just went for it.

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DIY Pneumatic Skeleton And Air Horn Gag To Scare Those Trick-Or-Treaters

October 19, 2013 by Todd Harrison 13 Comments

[Rick Osgood] has been busy making more scaring gags for Halloween. This week he’s sharing great ideas for an air horn and pneumatic jumping skeleton, both actuated by 24 V sprinkler valves. These two new gags can easily be activated using [Rick’s] cardboard floor plate switch and three 9 V batteries cleverly snapped together in series for a 27 V supply (we can’t resist dropping in this link to a 2196 V supply from 9 V batteries just for fun).

The air horn construction is quite unique using a latex balloon strategically located as a reed valve for the air to vibrate over as it rushes out making a very loud honking sound. [Rick] then connected his manual bicycle pump to an air supply so that when an air valve is actuated the bicycle pump handle with a skeleton wired to it pops up. It then lowers back down via a bleed hole in the air line. Both the air horn and pneumatic pop-up skeleton seem simple to construct and his tests show them functioning perfectly.

Being the air storage chambers are small the re-trigger setup seems too repetitive to be practical for a continuous stream of Trick-Or-Treaters. Perhaps one could hide an air compressor with a long feed line to supply the gags? Plus, using an air compressor would come in handy for other scary blasts of air. Of course you would want to lower the compressor’s output regulator to safe levels so you don’t risk blowing apart your pop-up skeleton rig or any pipes.

Follow along after the break to see how to build these two great gags and get some tips from Mr. Safety.

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