Tag Archives: Radio

TEMPEST In A Software Defined Radio

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In 1985, [Wim van Eck] published several technical reports on obtaining information the electromagnetic emissions of computer systems. In one analysis, [van Eck] reliably obtained data from a computer system over hundreds of meters using just a handful of components and a TV set. There were obvious security implications, and now computer systems handling highly classified data are TEMPEST shielded – an NSA specification for protection from this van Eck phreaking.

Methods of van Eck phreaking are as numerous as they are awesome. [Craig Ramsay] at Fox It has demonstrated a new method of this interesting side-channel analysis using readily …read more

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Decoding NRSC-5 with SDR to Get In Your Car

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NRSC-5 is a high-definition radio standard, used primarily in the United States. It allows for digital and analog transmissions to share the original FM bandwidth allocations. Theori are a cybersecurity research startup in the US, and have set out to build a receiver that can capture and decode these signals for research purposes, and documented it online.

Their research began on the NRSC website, where the NRSC-5 standard is documented, however the team notes that the audio compression details are conspicuously missing. They then step through the physical layer, multiplexing layer, and finally the application layer, taking apart the standard …read more

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Hackaday Prize Entry: Sub Gigahertz RF

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For all the press WiFi and Bluetooth-connected Internet of Things toasters get, there’s still a lot of fun to be had below one Gigahertz. For his Hackaday Prize entry, [Adam] is working on an open source, extensible 915 and 433 MHz radio designed for robotics, drones, weather balloons, and all the other fun projects that sub-Gigaherts radio enables.

The design of this radio module is based around the ADF7023 RF transceiver, a very capable and very cheap chip that transmits in the usual ISM bands. The rest of the circuit is an STM32 ARM Cortex M0+, with USB, UART, and …read more

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A Tube AM Transmitter In A Soup Can

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A standard early electronics project or kit has for many years been the construction of a small broadcast transmitter with enough power to reach the immediate area, but no further. These days that will almost certainly mean an FM broadcast band transmitter, but in earlier decades it might also have been for the AM broadcast band instead.

The construction of a small AM transmitter presents some interesting problems for an electronic designer. It is extremely easy to make an AM transmitter with a single transistor or tube, but it is rather more difficult to make a good one. The modulation …read more

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A Remotely Tuned Magnetic Loop Antenna

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If you are a radio amateur, you may be familiar with the magnetic loop antenna. It’s different from most conventional wire antennas, taking the form of a tuned circuit with a very large single-turn coil and a tuning capacitor. Magnetic loops have the advantage of extreme selectivity and good directionality, but the danger of a high voltage induced across that tuning capacitor and the annoyance of needing to retune every time there is a frequency change.

[Oleg Borisov, RL5D] has a magnetic loop, and soon tired of the constant retuning. His solution is an elegant one, he’s made a remote …read more

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Phase Modulation With An FPGA

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There are two radio modulation schemes everyone should know. Amplitude modulation changes the amplitude — or ‘volume’, if you will — of a carrier frequency and turns all radio into channels owned and operated by a church. Frequency modulation changes the pitch of a carrier frequency and is completely run by Clear Channel. Amateur radio operators are familiar with dozens of other modulation schemes, but there’s one hardly anyone touches. Phase modulation is weird and almost unheard of, but that doesn’t mean you can’t implement it on an FPGA. [nckm] is transmitting audio using phase modulation on an FPGA  …read more

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Simple Range Testing for LoRa Modules

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WiFi and Bluetooth have their use cases, but both have certain demands on things like battery life and authentication that make them unsuitable for a lot of low-power use cases. They’re also quite limited in range. There are other standards out there more suitable for low-power and wide area work, and thankfully, LoRa is one of them. Having created some LoRa pagers, [Moser] decided to head out and test their range.

Now, we’ve done range tests before. Often this involves sending one party out with a radio while the other hangs back at base. Cellphones serve as a communications link …read more

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Simple Range Testing for LoRa Modules

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WiFi and Bluetooth have their use cases, but both have certain demands on things like battery life and authentication that make them unsuitable for a lot of low-power use cases. They’re also quite limited in range. There are other standards out there more suitable for low-power and wide area work, and thankfully, LoRa is one of them. Having created some LoRa pagers, [Moser] decided to head out and test their range.

Now, we’ve done range tests before. Often this involves sending one party out with a radio while the other hangs back at base. Cellphones serve as a communications link …read more

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Pi Network Attenuators: Impedance Matching For The Strong Of Signal

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If you catch a grizzled old radio amateur propping up the bar in the small hours, you will probably receive the gravelly-voiced Wisdom of the Ancients on impedance matching, antenna tuners, and LC networks. Impedance at RF, you will learn, is a Dark Art, for which you need a lifetime of experience to master. And presumably a taste for bourbon and branch water, to preserve the noir aesthetic.

It’s not strictly true, of course, but it is the case that impedance matching at RF with an LC network can be something of a pain. You will calculate and simulate, but …read more

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