Measuring Spurious Emissions of Cheap Handheld Transceivers

If you buy an amateur transceiver cheap enough to make a reasonable grab bag gift or stocking stuffer, you get what you pay for. And if this extensive analysis of cheap radios is any indication, you get a little more than you pay for in the spurious emissions department.

Amateur radio in the United States is regulated by the FCC’s Part 97 rules with special attention given to transmitter technical specifications in Subpart D. Spurious emissions need to be well below the mean power of the fundamental frequency of the transmitter, and [Megas3300] suspected that the readily available Baofeng UV-5RA dual-band transceiver was a little off spec. He put the $20 radio through a battery of tests using equipment that easily cost two orders of magnitude more than the test subject. Power output was verified with a wattmeter, proper attenuators were selected, and the output signal scanned with a spectrum analyzer. Careful measurements showed that some or all of the Baofeng’s harmonics were well above the FCC limits. [Megas3300] tested a few other radios that turned out to be mostly compliant, but however it all turned out, the test procedure is well documented and informative, and well worth a look.

The intended market for these radios is more the unlicensed crowd than the compliant ham, so it’s not surprising that they’d be out of spec. A ham might want to bring these rigs back into compliance with a low pass filter, for which purpose the RF Biscuit might prove useful.

[via r/AmateurRadio]

Real-Time Planet Tracker With Laser-Point Accuracy

Space. The final frontier. Unfortunately, the vast majority of us are planet-locked until further notice. If you are dedicated hobbyist astronomer, you probably already have the rough positions of the planets memorized. But what if you want to know them exactly from the comfort of your room and educate yourself at the same time? [Shubham Paul] has gone the extra parsec to build a Real-Time Planet Tracker that calculates their locations using Kepler’s Laws with exacting precision.

An Arduino Mega provides the brains, while 3.5-turn-pan and 180-degree-tilt servos are the brawn. A potentiometer and switch allow for for planet and mode selection, while a GPS module and an optional MPU9250 gyroscope/magnetometer let it know where you are. Finally a laser pointer shows the planet’s location in a closed room. And then there’s code: a lot of code.

The hardware side of things — as [Shubham Paul] clarifies — looks a little unfinished because the focus of the project is the software with the intent to instruct. They have included all the code they wrote for the RTPT, providing a breakdown in each section for those who are looking to build their own.

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Rotary Telephone Becomes Stylish Lamp

The vintage aesthetic is more popular than ever, and while things like rotary phones aren’t particularly useful anymore, there’s a lot of fun to be had using them in new and inventive ways. For this project, [Sander] built an attractive table lamp out of a Siemens rotary phone.

Switched off, the lamp appears to be nothing more than a phone with its handset floating in midair. However turn the dial, and LEDs mounted in the receiver begin to glow. Taking things a step further as good hackers do, [Sander] used a motorised potentiometer to control the LED brightness with a NodeMCU board featuring the ESP8266. This allows the LEDs to be dimmed either by hand, or by a smartphone connected over WiFi, without the dial getting out of sync.

By using a dual H-bridge setup, the NodeMCU is able to both control the motorized pot as well as generate an AC signal to activate the original bell in the phone, which adds a whole lot of nostalgia points. Fitting the motorized pot into the phone did lend some challenges but that didn’t slow [Sander] down – they simply used a cheap universal joint to allow the motor to connect to the rotary dial off-axis. A great trick to keep in your back pocket.

For the haunting floating effect, [Sander] used a meter of 4 mm brass rod, bending it into shape to hold up the handset. This was used as a ground, and along with a couple of extra wires for power, was covered in a black textile sheath recovered from another electrical cable. [Sander] tells us it wasn’t the easiest thing to pull off, but we definitely agree that the effect is totally worth it.

Thirsty for more vintage ephemera? Check out this rotary phone that runs on GSM. Video below the break.

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Google Scrubs Brillo, Reveals Android Things

Another week goes by and another new IoT platform surfaces. Google has announced Android Things, a build of the mobile operating system designed for smart devices rather than the latest slab of mobile eye-candy. The idea is that the same Android tools, framework and APIs that will already be familiar to app developers can be used seamlessly on IoT Things as well as in the user’s palm.

Of course, if this is sounding familiar, it’s because you may have heard something of it before. Last year they announced their Project Brillo IoT platform, and this appears to be the fruit of those efforts.

So you may well be asking: what’s in it for us? Is this just another commercial IoT platform with an eye-watering barrier to entry somewhere, or can we join the fun? It turns out the news here is good, because as the project’s web site reveals, there is support for a variety of Intel, NXP, and Raspberry Pi development boards. If you have a Raspberry Pi 3 on your bench somewhere then getting started is as simple as flashing a disk image.

The Things team have produced a set of demonstration software in a GitHub repository for developers to get their teeth into. Never one to miss an opportunity, the British Raspberry Pi hardware developer Pimoroni has released an Android Things HAT laden with sensors and displays for it to run on.

The IoT-platform market feels rather crowded at times, but it is inevitable that Android Things will gain significant traction because of its tight connections with the rest of the Android world, and its backing by Google. From this OS will no doubt come a rash of devices that will become ubiquitous, and because of its low barrier to entry there is every chance that one or two of them could come from one of you. Good luck!

Chris Conlon: Device Security 101

We all wring our hands over the security (or lack thereof!) of our myriad smart devices. If you haven’t had your home network hacked through your toaster, or baby cam, you’re missing out on the zeitgeist. But it doesn’t have to be this way — smart devices can be designed with security in mind, and [Chris Conlon] came to Pasadena to give us a talk on the basics.

He starts off the talk with three broad conceptual realms of data security: data in transit, data at rest on the device, and the firmware and how it’s updated. A common thread underlying all of this is cryptography, and he devotes the last section of his  talk to getting that right. So if you’d like a whirlwind tour of device security, watch on!

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A How-To in Homebrew Design, Fab, and Assembly with Structural Framing Systems

At this point, the internet is crawling with butt-kicking homebrew 3D printers made with extruded profiles, but it’s easy to underestimate the difficulty in getting there. Sure, most vendors sell a suite of interlocking connectors, but how well do these structural framing systems actually fare when put to the task of handling a build with sub-millimeter tolerances?

I’ve been playing around with these parts for about two years. What I’ve found is that, yes, precise and accurate results are possible. Nevertheless, those results came to me after I failed and–dry, rinse, repeat–failed again! Only after I understood the limits of both the materials and assembly processes was I able to deliver square, dimensionally accurate gantries that could carry a laser beam around a half-square-meter workbed. That said, I wrote a quick guide to taming these beasts. Who are they? What flavors do they come in? How do we achieve those precision results? Dear reader, read on.

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Converting Film Camera to Digital the Hard Way

[Robin] is a hobby photographer with some very nice old film camera gear. But who has the money or patience for developing film these days? (Well, lots of people, especially artists, but that’s a different Hackaday article.) So to update his old gear without breaking the bank, he glommed a Sony Nex digital camera onto the back of a nice old Nikon, and documented the process for us.

A friend of mine once said, “never underestimate what a good engineer can do with a file and patience.” [Robin]’s hack essentially consists of grinding the Sony’s CMOS sensor to fit exactly where the film plane would be in the old Nikon. For him, this meant relocating the IR filter glass, because it wouldn’t fit with the shutter, and then slowly and accurately trimming down the edges of the CMOS sensor’s retaining frame until it was just right.

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