A Dead Simple, Well Constructed FM Transmitter

July 30, 2014 by Brian Benchoff 54 Comments

[Angelo] is only 15, but that doesn’t mean his fabrication skills are limited to Lego and K’Nex. He’s built himself an amazingly well constructed FM transmitter that’s powerful enough to be received a quarter mile away.

The FM transmitter circuit itself is based off one of [Art Swan]’s builds, but instead of the solderless breadboard construction you would expect to find in a small demo circuit, [Angelo] went all the way, etching his own PCB and winding his own coil.

Using photosensitized copper clad board, [Angelo] laid out the circuit with Fritzing, etched a board, and went at it with a drill. The components found in the transmitter are pretty standard and with the exception of the trimmer cap and electret mic, can be picked up in the parts drawers of any Radio Shack. He gets bonus points for using a 1/4 – 20 bolt for winding the coil, too.

The power supply for the transmitter is a single 9V battery, the battery connector being salvaged from a dead 9V. Awesome work, and for someone so young, [Angelo] already seems to have a grasp of all the random, seemingly useless information that makes prototyping so much easier. Video below.

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Fishing For Radio Signals With The Moxon Antenna

July 23, 2014 by Adam Fabio 4 Comments

mox-antenna

[Bill Meara] has finished his latest project, a Moxon antenna for HF on 17 meters. [Bill] is well-known here on Hackaday. When not building awesome radios, he can be found ranting about ham radio. His new antenna turned out to be a true hack. He even used a hacksaw to build it!

The Moxon antenna is named for the late [Les Moxon, G6XN] who first described it in “Two-Element Driven Arrays”, a QST magazine article published in July of 1952. [Bill] built his Moxon loosely based on [Jim/AE6AC’s] excellent instructions. The design is incredibly simple – a two element directional antenna using crappie fishing poles as spreaders. That’s crappie as in the fish, not the quality of the pole. Crappie poles are typically made up of telescoping sections of graphite or fiberglass in common lengths of 14, 16, and 20 feet. The poles can be bought for under $20 at sporting goods stores. [Bill] used 16 foot poles purchased from Amazon.

The antenna is created by connecting all four poles at their bases in an X shape. The wire elements are stretched across the ends of the poles. The entire antenna bends up as the stiff poles hold the driven and reflector elements in tension. [Bill] used some scrap wood and U-bolts to attach the fishing poles, and bungee cord ends at the tips. Since the antenna is directional, [Bill] added a TV antenna rotor to spin the beam around. The antenna is so light that one could get by with a couple of cords and the “Armstrong method” of antenna rotation.

Once up on the roof, [Bill] found his antenna really performed. He was easily able to cross the Atlantic from his Northern Virginia home to France, Belgium, and Latvia. The mostly horizontal antenna makes it a bit more unobtrusive than other directional designs. [Bill] mentions that his neighbors haven’t revolted yet, so he’s continuing to enjoy the fruits of his antenna labors.

HOPE X: Creating Smart Spaces With ReelyActive

July 22, 2014 by Brian Benchoff 10 Comments

When we hear about the Internet of Things, we’re thinking it’s a portable device with a sensor of some kind, a radio module, and the ability to push data up to the Internet. There’s nothing that says a device that puts data on the Internet has to be portable, though, as [Jeff] from ReelyActive showed us at HOPE X last weekend.

[Jeff]’s startup is working on a device that turns every space into a smart space. It does this with radio modules connected to a computer that listen to Bluetooth and the 868, 915 and 2400MHz bands. These modules turn every place into a smart space, identifying who just walked into a room, and who is at a specific location. Think of it as the invisible foundation for any truly smart house.

The radio modules themselves are daisychained with Cat5 cable, able to be plugged into a hub or existing Ethernet drops. The software that makes the whole thing work can run on just about anything; if you want a Raspi to turn on the lights when you enter a room, or turn off a thermostat when you leave a building, that’s just a few lines of code and a relay.

The software is open source, and [Jeff] and his team are looking at making the hardware open. It’s a great idea, and something that would be a good entry for The Hackaday Prize, but ReelyActive is located in Montréal, and like Syria and North Korea, we’re not allowed to run a contest in Quebec.

HOPE X: Citizens Band Microwave Spectrum And Free Internet For All

July 21, 2014 by Brian Benchoff 20 Comments

hopex_web_topbar_b

The bulk of HOPE X was the talks, but arguably the far more interesting aspect of thousands of hackers and tinkerers under one roof is talking to everyone about what they’re doing. One guy hanging out at HOPE gave a quick lightning talk to a few people about something very interesting: something the FCC is pushing through that’s open to just about everything: it’s the FCC’s new CB radio service (you’ll want to click the presentation link at the very top of the page), giving anyone, not just people with a radio license, access to a huge swath of microwave spectrum.

The short version of the talk was the fact the FCC is extremely interested in opening up 100 to 200 MHz of spectrum at 3.5 GHz. The idea is to create something like cellular service that can either be implemented by companies, or normal, everyday people. The initial goal of this is to provide -possibly- free Internet to anyone with the right USB dongle. Since it’s just radio, and open to everyone, just about anything can be implemented.

This is something the FCC, Google, Microsoft, and a whole bunch of startups are extremely interested in, and the fact that about half of the spectrum will be open to anyone creates some interesting opportunities. A community-based freenet of wireless Internet links becomes an easy solution, and since the hardware to access 3.5 GHz is similar to other hardware that’s already available means building your own wireless ISP could be relatively easy in 12 to 18 months.

A transcript of the lightning talk is available below.

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Vintage Radio Rocks With Modern Technology

July 11, 2014 by Will Sweatman 24 Comments

old soviet transistor radio

[Madis] had an old Soviet Russian Neywa 402 transistor radio sitting on the shelf. It looked cool, but unfortunately that’s about all it did. Built in the 70’s one can only wonder about the past life of the radio. And one can only wonder what the past owner thought about the future of it, if they thought about it at all? Would they have thought that several decades in the future, a hardware hacker would introduce some strange and mysterious technology to breath new life into it? Probably not. But that’s exactly what happened.

[Madis] picked up a Bluetooth speaker from Ebay for a whopping $10. And like any good hacker, he immediately took it apart and ditched the original speaker. Wired up to the vintage radio, the Bluetooth receiver can be charged via a USB cable, which neatly tucks away in the back of the case. And with a few taps of his smart phone, he can stream audio to his new vintage Bluetooth speaker.

Though a simple hack, [Madis] does a great job at breathing new life into an antique electronic device. Check out the video after the break for a demonstration.

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A GSM Base Station With Software Defined Radio

July 5, 2014 by Brian Benchoff 40 Comments

gsm If you’re wondering how to get a better signal on your cellphone, or just want to set up your own private cell network, this one is for you. It’s a GSM base station made with a BeagleBone Black and a not too expensive software defined radio board.

The key component of this build is obviously the software defined radio. [Julian] is using a USRP B200 radio for this project. It’s not cheap, but it is a very nice piece of hardware capable of doing just about anything with GNU Radio. This board is controlled by a BeagleBone Black, a pretty cheap solution that puts the total cost of the hardware somewhere around $750.

The software side of the build is mostly handled by OpenBTS, the open source project for the software part of a cell station. This controls the transceiver, makes calls and SMS, and all the backend stuff every other cell station does. OpenBTS also includes support for Asterisk, the software of choice for PBX and VoIP setups. Running this allows you to make calls and send texts with your SDR-equipped, Internet-enabled BeagleBone Black anywhere on the planet.

A SI5351 clock generator chip and an Arduino

Generate Clocks With The SI5351 And An Arduino

June 27, 2014 by Eric Evenchick 10 Comments

If you’re dealing with RF, you’ll probably have the need to generate a variety of clock signals. Fortunately, [Jason] has applied his knowledge to build a SI5351 library for the Arduino and a breakout board for the chip.

The SI5351 is a programmable clock generator. It can output up to eight unique frequencies at 8 kHz to 133 MHz. This makes it a handy tool for building up RF projects. [Jason]’s breakout board provides 3 isolated clock outputs on SMA connectors. A header connects to an Arduino, which provides power and control over I2C.

If you’re looking for an application, [Jason]’s prototype single-sideband radio shows the chip in action. This radio uses two of the SI5351 clocks: one for the VFO and one for the BFO. This reduces the part count, and could make this design quite cheap.

The Arduino library is available on Github, and you can order a SI5351 breakout board from OSHPark.