Radio Hacks

1319 Articles

A New Digital Mode For Radio Amateurs

March 31, 2019 by 65 Comments

There used to be a time when amateur radio was a fairly static pursuit. There was a lot of fascination to be had with building radios, but what you did with them remained constant year on year. Morse code was sent by hand with a key, voice was on FM or SSB with a few old-timers using AM, and you’d hear the warbling tones of RTTY traffic generated by mechanical teletypes.

By contrast the radio amateur of today lives in a fast-paced world of ever-evolving digital modes, in which much of the excitement comes in pushing the boundaries of what is possible when a radio is connected to a computer. A new contender in one part of the hobby has come our way from [Guillaume, F4HDK], in the form of his NPR, or New Packet Radio mode.

NPR is intended to bring high bandwidth IP networking to radio amateurs in the 70 cm band, and it does this rather cleverly with a modem that contains a single-chip FSK transceiver intended for use in licence-free ISM band applications. There is an Ethernet module and an Mbed microcontroller board on a custom PCB, which when assembled produces a few hundred milliwatts of RF that can be fed to an off-the-shelf DMR power amplifier.

Each network is configured around a master node intended to use an omnidirectional antenna, to which individual nodes connect. Time-division multiplexing is enforced by the master so there should be no collisions, and this coupled with the relatively wide radio bandwidth of the ISM transceiver gives the system a high usable data bandwidth.

Whether or not the mode is taken up and becomes a success depends upon the will of individual radio amateurs. But it does hold the interesting feature of relying upon relatively inexpensive parts, so the barrier to entry is lower than it might be otherwise. If you are wondering where you might have seen [F4HDK] before, we’ve previously brought you his FPGA computer.

Bidirectional IP With New Packet Radio

March 30, 2019 by 24 Comments

There are a few options if you want to network computers on amateur radio. There are WiFi hacks of sort, and of course there’s always packet radio. New Packet Radio, a project from [f4hdk] that’s now on hackaday.io, is unlike anything we’ve seen before. It’s a modem that’s ready to go, uses standard 433 ISM band chips, should only cost $80 to build, and it supports bidirectional IP traffic.

The introductory documentation for this project (PDF) lays out the use case, protocol, and hardware for NPR. It’s based on chips designed for the 433MHz ISM band, specifically the SI4463 ISM band radio from Silicon Labs. Off the shelf amplifiers are used, and the rest of the modem consists of an Mbed Nucleo and a Wiznet W5500 Ethernet module. There is one single modem type for masters and clients. The network is designed so that a master serves as a bridge between Hamnet, a high-speed mesh network that can connect to the wider Internet. This master connects to up to seven clients simultaneously. Alternatively, there is a point-to-point configuration that allows two clients to connect to each other at about 200 kbps.

Being a 434 MHz device, this just isn’t going to fly in the US, but the relevant chip will work with the 915 MHz ISM band. This is a great solution to IP over radio, and like a number of popular amateur radio projects, it started with the hardware hackers first.

Executing A Vehicle Keyless Entry Attack

March 30, 2019 by 1 Comment

You read about well-publicised security exploits, but they always seem to involve somebody with a deity’s grasp of whatever technology is being employed, as well as a pile of impossibly exotic equipment. Surely a mere mortal could never do that!

Happily, that’s not always the case, and to prove it [Gonçalo Nespral] replicated an attack against RF devices such as some garage doors and motor vehicle locks that use a rolling code. His inspiration came from a device from2015, that encouraged the owner of a key to keep transmitting fresh codes. It did this by swamping the receiver of the car, garage door, or whatever with a strong slightly off frequency signal. This would cause the lock to not work, so the user would try again and again. The attacker listens with a very narrow bandwidth receiver on-frequency that is good enough to reject the jamming signal, and can harvest a sequence of the rolling codes enough to compromise it.

[Gonçalo]’s set-up uses a YARD stick One transceiver dongle as its transmitter, and an RTL-SDR for receive. A GNU Radio setup is used to retrieve the key data, and some custom Python code does the remaining work. We wouldn’t advocate using this in the wild and it could conceivably also gain you access to another car with a flashing light on top, but it’s an interesting exposé of the techniques involved.

Rolling code keyfob attacks are something we covered a few years ago, back when these attacks were all shiny and new.

Emergency Neighbourhood Communications Courtesy Of HELPER

March 29, 2019 by 23 Comments

For many people, phone and Internet connectivity are omnipresent and always available. It’s possible to upload selfies from a Chinese subway, and search for restaurant reviews in most highway towns, all thanks to modern cellular connectivity. However, in emergencies, we’re not always so lucky. If towers fail or user demand grows too large, things can collapse all too quickly. It’s in these situations that HELPER aims to flourish.

HELPER stands for Heterogeneous Efficient Low Power Radio. It’s a radio system designed to operate in the absence of any infrastructure, creating a pop-up network to serve community needs in disaster areas. Users can share information about available resources, like water, gasoline and food, while emergency workers can coordinate their response and direct aid to those who need it.

It’s a system built around commonly available parts. Raspberry Pis run the back end software and communicate with individuals over WiFi, with LoRa radios handling the longer-range communication from node to node. Combining this communication ability with GPS location and stored map data allows users to more easily find resources and assistance when things go wrong. The journal article is freely available for those wishing to learn more about the project.

It’s a project which aims to keep people safe when conventional networks go down. The key is to remember that once disaster strikes, it’s usually too late to start distributing radio hardware – emergency gear should be in place well before things start to go south. Of course, there’s also the government side of the equation – in the USA, the Emergency Broadcast System is a great example of emergency communications done right. Video after the break.

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Custom LoRa Pager Designed With Care

March 24, 2019 by 13 Comments

LoRa is a useful technology if you need to send data a long way at low power levels. Leveraging this, [5Volt-Junkie] decided to build a small pager named the LoRaNicator.

Those who love a detailed build log will enjoy this. The pager features everything up to and including the kitchen sink. A Cortex M0+ runs the show, flashed with an Arduino compatible bootloader, while a RFM95W module handles the LoRa communications. There’s a pager vibrator and piezo buzzer for notifications, along with a LiPo charger to make keeping the battery topped up easy. There’s even an RTC and soft-power button module.

Even if the LoRa side of things isn’t relevant to your interests, it’s a great example of how to build a useful tool rather than just a proof-of-concept. Things like an easy-to-use interface and simple battery charging go a long way to making something usable in the field. [5Volt-Junkie] even goes so far as to point out that even solder mask matters – if you’re using an infrared oven, your black boards will need a different profile to the usual green PCBs.

All the hard work has paid off, creating an attractive end product that we’d be proud to pack with the rest of our ham gear. LoRa is a useful platform, and as we’ve seen, it can be useful for everything from viticulture to meterology. Video after the break.

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Making A 1940s Radio Digital With Nixies

March 17, 2019 by 10 Comments

Classix Philly One Oh Seven Nine is your home for Philly soul right at the top of the dial. That phrase, ‘top of the dial’ doesn’t mean much these days because we all have radios with a digital display and seek buttons. There was a time when radios actually had dials, but [glasslinger] is in a class all by himself. He’s adding a digital display to a 1940s radio, and he’s doing it with Nixie tubes.

The circuitry for the digital display for this AM radio requires getting the frequency the radio is tuned to. This is done by counting the oscillator frequency, then subtracting the IF. [glasslinger] is doing this with an Arduino (hey, it’s a legitimate engineering choice) and a 4040 12-bit binary counter as a pre-scaler. The Arduino does the math and then drives a few 74141 Nixie drivers, which then display the frequency of the receiver in beautiful glass tubes. Add in a single neon bulb for the thousands digit, and you have a four-digit display that will tell you the frequency you’re tuned to on an old AM radio.

The rest of the build consists of fixing up an old radio and gluing the veneer down again with modern glues that will last another seventy years. The finished cabinet was sanded, a bezel for the display was added, and since [glasslinger] has the equipment, he made a new, long neon tube to light up with the volume of the radio. And you thought a cat’s eye detector was cool.

This build is a tour de force, and something that is so incredibly modern but at the same time built on vintage technology. If you’ve got an hour and a half, we highly recommend checking out the build video below.

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Building A Magnetic Loop Antenna

March 17, 2019 by 21 Comments

Antennas come in many shapes and sizes, with a variety of characteristics making them more or less suitable for various applications. The average hacker with only a middling exposure to RF may be familiar with trace antennas, yagis and dipoles, but there’s a whole load more out there. [Eric Sorensen] is going down the path less travelled, undertaking the build of a self-tuning magnetic loop antenna. 

[Eric]’s build is designed to operate at 100W on the 20 meter band, and this influences the specifications of the antenna. Particularly critical in the magnetic loop design is the voltage across the tuning capacitor; in this design, it comes out at approximately 4 kilovolts. This necessitates the careful choice of parts that can handle these voltages. In this case, a vacuum variable capacitor is used, rated to a peak current of 57 amps and a peak voltage of 5 kilovolts.

The magnetic loop design leads to antenna which is tuned to a very narrow frequency range, giving good selectivity. However, it also requires retuning quite often in order to stay on-band. [Eric] is implementing a self-tuning system to solve this, with a controller using a motor to actuate the tuning capacitor to maintain the antenna at its proper operating point.

If you’re unfamiliar with magnetic loop builds, [Eric]’s project serves as a great introduction to both the electrical and mechanical considerations inherent in such a design. We’ve seen even more obscure designs though – like these antennas applied with advanced spray techniques.