Radio Hacks

1322 Articles

Tracking Boats And Ships In Real Time At The Same Time

October 22, 2020 by 15 Comments

Software-defined radio came on the hacker scene in a big way less than a decade ago thanks to the discovery that a small USB-based TV tuner dongle could be used for receiving all kinds of radio transmissions. Two popular projects from that era are tracking nearby airplanes and boats in real time. Of course, these projects rely on different frequencies and protocols, but if you live in a major port city like [Ian] then his project that combines both into a single user interface might be of interest.

This project uses an RTL-SDR dongle for the marine traffic portion of the project, but steps up to a FlightAware Pro dongle for receiving telemetry from airplanes. Two separate antennas are needed for this, and all of the information is gathered and handled by a pair of Raspberry Pis. The Pis communicate with various marine and air traffic databases as well as handles the custom user interface that knits both sets of information together. This interface was custom-built from a previous project of his and was repurposed slightly to fit the needs of this one.

This is a great project that goes into a lot of interesting detail about how the web traffic moves and how the UI works, so even if you’re not into software-defined radio it might be worth a look. However, it’s also worth noting that it hasn’t been easier to set up a system like this thanks to the abundance and low price of RTL-SDR dongles and the software tools that make setting them up a breeze.

It Came From Outer Space: Listening To The Deep Space Network

October 17, 2020 by 26 Comments

Ham radio operators love to push the boundaries of their equipment. A new ham may start out by making a local contact three miles away on the 2m band, then talk to somebody a few hundred miles away on 20m. Before long, they may find themselves chatting to fellow operators 12,000 miles away on 160m. Some of the adventurous return to 2m and try to carry out long-distance conversations by bouncing signals off of the Moon, waiting for the signal to travel 480,000 miles before returning to Earth. And then some take it several steps further when they listen to signals from spacecraft 9.4 million miles away.

That’s exactly what [David Prutchi] set out to do when he started building a system to listen to the Deep Space Network (DSN) last year. The DSN is NASA’s worldwide antenna system, designed to relay signals to and from spacecraft that have strayed far from home. The system communicates with tons of inanimate explorers Earth has sent out over the years, including Voyager 1 & 2, Juno, and the Mars Reconnaissance Orbiter. Because the craft are transmitting weak signals over a great distance (Voyager 1 is 14 billion miles away!), the earth-based antennas need to be big. Real big. Each of the DSN’s three international facilities houses several massive dishes designed to capture these whispers from beyond the atmosphere — and yet, [David] was able to receive signals in his back yard.

Sporting a stunning X-band antenna array, a whole bunch of feedlines, and some tracking software, he’s managed to eavesdrop on a handful of spacecraft phoning home via the DSN. He heard the first, Bepi-Colombo, in May 2020, and has only improved his system since then. Next up, he hopes to find Juno, and decode the signals he receives to actually look at the data that’s being sent back from space.

We’ve seen a small group of enthusiasts listen in on the DSN before, but [David]’s excellent documentation should provide a fantastic starting point for anybody else interested in doing some interstellar snooping.

The Cable Modem To SDR Transformation

October 10, 2020 by 5 Comments

What do you do with an old cable modem in a closet? If you are [stdw] you reverse engineer it and turn it into a software-defined radio. The modem in question was a Motorola MB7220. After looking at a similar project using a different modem, it seemed like it should be doable.

Cracking open the case revealed two likely UART ports, one of which was active. The output from that UART provided a lot of info. The chip was a Broadcom BCM3383 which is a MIPS processor. It had eCos as an operating system. However, the bootloader eventually disables the UART, so there wasn’t much more investigation possible via the serial terminal.

The next step was to dump the flash memory. That required a little solder surgery to prevent the board from starting while the flash chip had power. It appeared that some key credentials and configuration data were present, but they were really backups. After doing a factory reset to remove the backups, the right data was apparent.

After some lengthy exploration, the diagnostic that builds a spectrum display gave up its data. At first, the data was just a small sample of what was really required, but it did show a local FM station as a spectrum. Eventually, the data loss rate was down to about 12% when streaming which is not great, but good enough. You can hear an audio clip of the reception. Not exactly crystal-clear quality, but not bad.

Of course, no one will use this for an FM radio. But it is a fascinating view into how far you can hack into a device like this if you have some skills and patience. There must be something about quarantine that is making people hack old gear, as we just recently saw a similar Netgear hack. Even cheap games aren’t safe.

Long Range WiFi Broadcasts Open-Source Video Conferencing

October 10, 2020 by 18 Comments

WiFi is an ubiquitous feature of the modern landscape, but due to power restrictions on most hardware alongside the high-frequency signal it’s typically fairly limited in range. This of course leads to frustration where a WiFi signal can be seen, but the connection is unreliable or slow. While most would reach for a range extender or other hardware bridge, [tak786] was able to roll out a better solution for his workplace by using a high-gain antenna and a single-board computer which gets him an amazing kilometer-wide WiFi network.

The build uses a 10 dBi antenna from TP-Link that’s rated for outdoor use and a single-board computer which acts as a sort of router. The antenna is placed at the top of a building which certainly helps with the extreme range as well. This setup doesn’t actually broadcast an open Internet connection, though. [tak786]’s employer needed a teleconferencing solution for their building, and he also created a fully open-source video conferencing solution called trango that can run on any LAN and doesn’t require an Internet connection. The WiFi setup in this build is effectively just a bonus to make the conferencing system more effective.

[tak786] is planning on releasing a whitepaper about this build shortly, but for now you can access the source code for the video conferencing system at his GitHub page. And, before anyone jumps to conclusions, apparently this is well within FCC rules as well. Some of the comments in the linked Reddit post suggest that with an amateur radio license this system could be pushed much further, too. If you need more range than a kilometer, though, it’s not too much more difficult to do once you have all the right hardware.

M17 Aims To Replace Proprietary Ham Radio Protocols

October 2, 2020 by 115 Comments

While M17 might sound like a new kind of automatic rifle (as actually, it is), we were referring to an open source project to create a ham radio transceiver. Instead of paraphrasing the project’s goals, we’ll simply quote them:

The goal here should be to kick the proprietary protocols off the airwaves, replace DMR, Fusion, D-Star, etc. To do that, it’s not just good enough to be open, it has to be legitimately competitive.

Like some other commercial protocols, M17 uses 4FSK along with error correction. The protocol allows for encryption, streaming, and the encoding of callsigns in messages. There are also provisions for framing IP packets to carry data. The protocol can handle voice and data in a point-to-point or broadcast topology.

Continue reading “M17 Aims To Replace Proprietary Ham Radio Protocols” →

KiwiSDR Vs RaspberrySDR — A Tale Of Two SDRs

September 30, 2020 by 45 Comments

Once you move away from the usual software defined radio (SDR) dongles, you have only a few choices unless you want to drop some serious cash. One common hobby-grade SDR is the KiwiSDR. This popular unit runs Linux and can receive up to 30 MHz. The platform uses a dedicated A/D converter, an FPGA, and BeagleBone computer. Success of course breeds imitators, and especially when you have an open source design like the Kiwi, you are going to find similar devices with possibly different end goals. That’s how the RaspberrySDR came to be. This is a very similar unit to the KiwiSDR but it uses a Raspberry Pi, along with a handful of other differences. What’s different? [KA7OEI] tells us in a recent blog post.

Other than the obvious difference of the computer and all that it entails, the RaspberrySDR has a higher speed A/D (125 MHz vs 66 MHz) and 16-bits of resolution instead of the Kiwi’s 14 bits. This combines to give the Raspberry a wider receive range (up to 60 MHz) and — in theory — better performance in terms of dynamic range and distortion.

Continue reading “KiwiSDR Vs RaspberrySDR — A Tale Of Two SDRs” →

Tracking Down Radio Frequency Noise Source, With Help From Mother Nature

September 25, 2020 by 18 Comments

Amateur radio operators and shortwave listeners have a common enemy: QRM, which is ham-speak for radio frequency interference caused by man-made sources. Indiscriminate, often broadband in nature, and annoying as hell, QRM spews forth from all kinds of sources, and can be difficult to locate and fix.

But [Emilio Ruiz], an operator from Mexico, got a little help from Mother Nature recently in his quest to lower his noise floor. Having suffered from a really annoying blast of RFI across wide swaths of the radio spectrum for months, a summer thunderstorm delivered a blessing in disguise: a power outage. Hooking his rig up to a battery — all good operators are ready to switch to battery power at a moment’s notice — he was greeted by blessed relief from all that noise. Whatever had caused the problem was obviously now offline.

Rather than waste the quiet time on searching down the culprit, [Emilio] worked the bands until the power returned, and with it the noise. He killed the main breaker in the house and found that the noise abated, leading him on a search of the premises with a portable shortwave receiver. The culprit? Unsurprisingly, it was a cheap laptop power supply. [Emilio] found that the switch-mode brick was spewing RFI over a 200-meter radius; a dissection revealed that the “ferrite beads” intended to suppress RFI emissions were in fact just molded plastic fakes, and that the cord they supposedly protected was completely unshielded.

We applaud [Emilio]’s sleuthing for the inspiration it gives to hunt down our own noise-floor raising sources. It kind of reminds us of a similar effort by [Josh (KI6NAZ)] a while back.