Lock Your Keys In The Car On Purpose With Aluminum Foil

April 22, 2020 by Bryan Cockfield 74 Comments

[TJ] is a surfer, and drives his car to get to the beach. But when he gets there he’s faced with a dilemma that most surfers have: either put his key in your baggies (shorts) or wetsuit and hope it doesn’t get lost during a wipeout, or stash it on the rear wheel of his car. Hiding the keyfob by the car isn’t an option because it can open the car doors just by being in proximity to the car. He didn’t want to risk losing it to the ocean either, so he built a waveguide of sorts for his key out of aluminum foil that lets him lock the key in the car without locking himself out.

Over a series of trials, [TJ] found out that his car, a 2017 Chevy Cruze, has a series of sensors in it which can determine the location of the keyfob based on triangulation. If it thinks the keyfob is outside of the car, it allows the door to be locked or unlocked with a button on the door handle. If the keyfob is inside the car, though, it prevents the car from locking via the door handles so you don’t accidentally lock yourself out. He found out that he could “focus” the signals of the specific sensors that make the car think the keyfob is outside by building an open Faraday cage.

The only problem now is that while the doors can be locked, they could also can be unlocked. To solve that problem he rigged up an ESP32 to a servo to open and close the opening in the Faraday cage. This still means there’s a hidden device used to activate the ESP32, but odds are that it’s a cheaper device to replace than a modern car key and improves security “through obscurity“. If you have any ideas for improving [TJ]’s build, though, leave them in the comments below. Surfers across the world from [TJ] to the author would be appreciative.

An FPGA And A Few Components Can Make A Radio

April 18, 2020 by Jenny List 18 Comments

There was a time when making a radio receiver involved significant work, much winding of coils, and tricky alignment of circuitry. The advent of Software Defined Radio (SDR) has moved a lot of this into the domain of software, but there is of course another field in which a radio can be created via code. [Alberto Garlassi] has created a radio receiver for the AM and HF bands with a Lattice MachXO2 FPGA and minimal external components.

He describes it as an SDR, which given that it’s created from Verilog, is a term that could be applied to it. But instead of using an SDR topology of ADC and digital signal processing, it implements a surprisingly traditional direct conversion receiver.

It has a quadrature AM demodulator which has a passing similarity to an SDR with I and Q phased signals, but that’s where the similarity ends. Frequency selection is via an oscillator controlled from a serial port, and there is even a PWM amplifier on board that can drive a speaker. The result can be seen in the video below, and as you can hear the direct conversion with quadrature demodulator approach makes for a very effective AM receiver.

If this is a little much but you still fancy a radio with minimal components, you should have a look at the Silicon Labs range of receiver chips.

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As A Matter Of Fact, It’s All Dark

April 16, 2020 by Bryan Cockfield 41 Comments

While the dark side of the moon wasn’t seen by humans until the middle of the 20th century, that side of the moon isn’t always dark, just hidden from view of Earth by a quirk of gravity. The more appropriate name for the other half of the moon is the “far side”, but while it gets just as much sunshine as the near side does it is dark to one thing in particular: man-made radio waves. That, along with the lack of an atmosphere and ionosphere on the moon, makes it a perfect place for a new telescope.

This telescope isn’t like something you’d set up in your back yard, either. It’s more similar to the Aricebo Observatory in Puerto Rico which uses natural topography to help form the telescope. The proposed telescope on the far side of the moon would use a robot to deploy a net along a fairly large crater to act as a parabolic dish, while another robot would suspend the receiver above the crater. The large size is necessary for viewing deep into space, but is also because of the low-frequency radio signals they hope to capture.

Building a dish like this on the moon is sure to be no easy task, especially since remote control on the far side of the moon is difficult for precisely the reasons that make this a good location for a telescope. But with an appropriate amount of funding and some sufficiently autonomous robots it should be possible. Plus, you never know what you’ll find when looking deep into space.

A Dangerous Demonstration Of The Power Of Radio

April 16, 2020 by Dan Maloney 56 Comments

Terrestrial radio may be a dying medium, but there are still plenty of listeners out there. What would a commute to or from work be without a check of “Traffic on the Eights” to see if you need to alter your route, or an update of the scores from yesterday’s games? Getting that signal out to as many listeners as possible takes a lot of power, and this dangerous yet fascinating demo shows just how much power there is on some radio towers.

Coming to us by way of a reddit post, the short video clips show a crew working on a 15,000-Watt AM radio tower. They appear to be preparing to do tower maintenance, which means de-energizing the antenna. As the engineer explains, antennas for AM radio stations in the medium-wave band are generally the entire tower structure, as opposed to the towers for FM and TV stations, which generally just loft the antenna as high as possible above the landscape. The fun starts when the crew disconnects a jumper and an arc forms across the clamp and the antenna feed. The resulting ball of plasma acts like a speaker, letting us clearly hear the programming on the station. It’s like one of the plasma speakers we’ve seen before, albeit exceptionally more dangerous.

It’s an impressive display of the power coursing through broadcast towers, and a vivid reminder to not mess with them. Such warnings often go unheeded, sadly, with the young and foolish paying the price. There’s a reason they put fences up around radio towers, after all.

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Pluto Might Not Be A Planet, But It Is An SDR Transceiver

April 14, 2020 by Al Williams 17 Comments

Many of the SDR projects we see use a cheap USB dongle. They are great, but sometimes you want more and — especially — sometimes you want to transmit. The Analog Devices ADALM-Pluto SDR is easily available for $200 and sometimes as low as $100 and it both transmits and receives using an Analog AD9363 and a Zynq FPGA. Although you normally use the device to pipe IQ signals to a host computer, you can run SDR applications on the device itself. That requires you to dig into the Zynq tools, which is fun but a topic for another time. In this post, I’m going to show you how you can use GNU Radio to make a simple Morse code beacon in the 2m ham band.

I’ve had one on my bench for quite a while and I’ve played with it a bit. There are several ways to use it with GNU Radio and it seems to work very well. You have to hack it to get the frequency range down a bit. Sure, it might not be “to spec” once you broaden the frequency range, but it seems to work fine. Instead of working from 325 MHz to 3,800 MHz with a 20 MHz bandwidth, the hacked device transceives 70 MHz to 6,000 MHz with 56 MHz bandwidth. It is a simple hack you only have to do once. It tells the device that it has a slightly better chip onboard and our guess is the chips are the same but sorted by performance. So while the specs might be a little off, you probably won’t notice.

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Hams Cross The Atlantic On UHF

April 13, 2020 by Al Williams 6 Comments

We often think of ham radio operators talking to exotic faraway lands, and that’s true for hams using the HF bands (below 30 MHz), especially if they have nice antennas. Modern living has made it much harder to have those big antenna farms, and today’s ham is more likely talking on VHF or UHF frequencies with very limited range under normal circumstances. Sure, you can use a repeater or bounce your signal from a satellite or the moon, but normal direct communication is normally going to be less than a typical commercial FM radio station. But on April 7th, two hams communicated across the Atlantic on 432 MHz — a UHF frequency. The distance was almost 4,000 km.

Notice we didn’t say they talked, but they communicated. The contact was via a somewhat controversial mode called FT8 which uses weak signal techniques to allow two computers to send limited amounts of information to each other. However, on April 10, the two stations reported a single sideband voice contact after they noticed the band conditions improving on the FT8 signal.

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Homebrew Loop Antenna Brings The Shortwave World To You

April 12, 2020 by Dan Maloney 36 Comments

Radio may be dead in terms of delivering entertainment, but it’s times like these when the original social network comes into its own. Being able to tune in stations from across the planet to get fresh perspectives on a global event can even be a life saver. You’ll need a good antenna to do that, which is where this homebrew loop antenna for the shortwave radio bands shines.

To be honest, pretty much any chunk of wire will do as an antenna for most shortwave receivers. But not everyone lives somewhere where it’s possible to string up a hundred meters of wire and get a good ground connection, which could make a passive loop antenna like this a good choice. Plus, loops tend to cancel the electrical noise that’s so part of life today, which can make it easier to pull in weak, distant stations.

[Thomas]’s design is based on a length of coaxial cable, which should be stiff enough to give the loop some stability, like a low-loss RG-8 or RG-213. The coax braid and dielectric are exposed at the midpoint of the cable to create a feed point, while the shield and center conductor at the other ends are cross-connected. A 1:1 transformer is wound on a toroid core to connect to the feedpoint; [Thomas] calls it a balun but we tend to think it’s more of an unun, since both the antenna and feedline are unbalanced. He reports good results from the loop across the shortwave band.

The shortwave and ham bands are a treasure trove of information and entertainment just waiting to be explored. Check them out — you might learn something, and you might even stumble across spies doing their thing.

[via RTL-SDR.com]