3D Printed Plane Flies High

One of our avid readers, [Niklas Melton] loves RC planes. After getting into 3D printing, the next logical step was to start building is own planes… And now he’s done it!

He calls it the Air-Form 1 Micro RC plane, paying homage to the FormLabs resin printer he used. All of the parts except for the electronics were printed using a tough resin. It’s designed to take balsa wood wings into clips he designed into the parts. A 150mAh battery provides the power with a motor that exerts about 54g of thrust — not bad considering the entire thing only weighs 60g! Unfortunately he doesn’t have any video clips of it flying, though he assures us it does indeed fly — if you’re interested in building your own, he’s uploaded all the files to a page on Thingiverse.

As more advanced 3D printers come down in price, like the SLA technology, it becomes possible to design and 3D print even more complex parts. Some of the resins available have now some pretty amazing properties. One of our readers replaced a servo spline gear with one he printed — which works even better than the original!


What do you get if you cross a software defined radio (SDR) and an iconic children’s drawing toy that we are sure is a trademarked name? If you are [devnulling], you wind up with the Etch-A-SDR. The box uses an Odroid C1, a Teensy, and the ubiquitous RTL-SDR.

The knobs work well as control knobs (as you can see in the video below). When you are bored listening to the radio, you can reset the box and go into Etch-a… um, drawing mode. The knobs work like you’d expect and you can even erase the screen with a vigorous shake.

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Minimal Mighty Mite

If you’re getting started building your own ham radio gear, it’s hard to imagine a more low-tech transmitter than the Mighty Mite, but [Paul Hodges, KA5WPL] took it one step further and rolled his own variable capacitor. (That’s the beer can with tape and alligator clips that you see on the left.)

A Mighty Mite is barely a radio at all. One transistor, capacitor, crystal and inductor in the form of a bunch of wire wrapped around a pill bottle form a minimalist oscillator, and then by keying this on and off with a switch, you’re sending Morse code. [Bill Meara], of the Soldersmoke Podcast, has been a passionate advocate of the Mighty Mite, suggesting that it can be made by scrounging the 3.57954 MHz colorburst crystal from an old analog TV set, which tunes the radio to a legal frequency for ham radio operators. (It will also probably work with other low-MHz crystals from your junkbox, but it won’t necessarily be legal.)

michigan_mighty_mite_schematicIf the crystal is “easily” scavengeable, and the rest of the radio is easily home-made, the tuning capacitor (obtainable from old AM/FM radios) can become the sticking point. So [Paul] cut up two aluminum “beverage” cans, wrapped the inner one in electrical tape, hooked up wires and made his own variable capacitor. By sliding the cans in or out so that more or less of them overlap, he can tune the radio to exactly the crystal’s natural frequency.

If you’re interested in building a Mighty Mite, you should definitely look at the topic on Soldersmoke. There are more build instructions online as well as plans for an optional filter to take off the harmonics if you’re feeling ambitious.

If you’re not a Morse code wiz, we can’t help but note that you could replace the key with a simple FET (we’d use a 2N7000, but whatever) and then you’ve got the radio under microcontroller control. Scavenge through Hackaday’s recent Morse code projects for ideas, and we’re sure you’ll come up with something good.

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Mid-Priced Hardware Gets Serious About Software Defined Radio

Regular Hackaday readers are used to seeing the hacks that use a cheap USB TV dongle as a software defined radio (SDR). There’s plenty of software that will work with them including the excellent GNU Radio software. However, the hardware is pretty bare-bones. Without modifications, the USB dongle won’t get lower frequencies.

There’s been plenty of other SDR radios available but they’ve had a much heftier price tag. But we recently noticed the SDRPlay RSP, and they now have US distribution. The manufacturer says it will receive signals with 12-bits of resolution over the range of 100 kHz to 2 GHz with an 8MHz bandwidth. The USB cable supplies power and a connection to the PC. The best part? An open API that supports Windows, Linux, Mac, Android, and will even work on a Raspberry Pi (and has GNU Radio support, too).

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Deep Sweep: A Home Made SigInt Platform

Signals Intelligence (SigInt) isn’t something that you normally associate with home hackers, but the Deep Sweep project is looking to change that: it is a balloon platform that captures radio signals in the stratosphere, particularly conversations between drones and satellites. Created by three students at the Frank Ratchye Studio for Creative Inquiry at Carnegie-Mellon, Deep Sweep is a platform that is attached to a balloon and which captures signals over a wide range of frequencies, logging them for later analysis. The current version captures data on three frequency bands: LF/HF (10KHz-30KHz), UHF (650 – 1650MHz) and SHF (10-20GHz). The latter are often the bands used for satellite links between drones and satellites. They are difficult to intercept from the ground, as the signals are directed upwards towards the satellite. By creating a platform that can fly several kilometers above the earth, they are hoping to be able to capture some of this elusive traffic.

So far, the team has made two flights in Europe, both of which encountered technical issues. The first had a battery fault and only captured 10 minutes of data, and the second flew further than expected and ended up in Belarus, a country that isn’t likely to welcome this kind of thing. Fortunately, they were able to recover the balloon and are working on future launches in Europe and the USA. It will be interesting to see how the Department of Homeland Security feels about this.

A Better Spectrum Analyzer for your Rigol Scope

The Rigol DS1000 series of oscilloscopes are popular with hobbyists for good reason: they provide decent specs at a low price. However, their spectrum analysis abilities are lacking. While these scopes do have a Fast Fourier Transform (FFT) function, it’s limited and nearly useless for RF.

A FFT plotted by the PyDSA tool and a Rigol oscilloscope[Rich] wanted a spectrum analyzer for amateur radio purposes, but didn’t want to build his own sampling hardware for it. Instead, he wrote PyDSA, a software spectrum analyzer for Rigol DS1000 oscilloscopes. This tool uses the USB connection on the scope to fetch samples, and does the number crunching on a far more powerful PC. It’s able to plot a 16,000 point FFT at two sweeps per second when run on a decent computer.

PyDSA is a Python script that makes use of the Virtual Instrument Software Architecture (VISA) interface to control the scope and fetch the sample data. Fortunately there’s some Python libraries that take care of the protocol.

[Rich] is now able to use his scope to measure amateur radio signals, which makes a nice companion to his existing Teensy based SDR project. If you have a Rigol, you can grab the source on Github and try it out.

Reverse Engineering Traffic Lights with Software Defined Radio

Construction crews tearing up the street to lay new internet fiber optic cable created a unique opportunity for [Bastian Bloessl]. The workers brought two mobile traffic lights to help keep the road safe while they worked. [Bastian] had heard that these lights use the 2 meter band radios, so he grabbed his RTL-SDR USB stick and started hacking. Mobile traffic lights are becoming more common in Europe. They can be controlled by a clock, traffic volume via an on-board camera, wire or radio. They also transmit status data, which is what [Bastian] was hoping to receive.

A quick scan with GQRX revealed a strong signal on 170.760 MHz. Using baudline and audacity, [Bastian] was able to determine that Audio Frequency Shift Keying was used to modulate the data. He created a simple receiver chain in GNU radio, and was greeted with a solid data stream from the lights. By watching the lights and looking at the data frames, [Bastian] was able to determine which bits contained the current light status. A quickly knocked up web interface allowed him to display the traffic light status in real-time.

It’s a bit scary that the data was sent in plaintext, however this is just status data. We hope that any command data is sent encrypted through a more secure channel.

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