Tag Archives: Radio

High Impedance Headphones? They’re In The Can!

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[George Trimble] likes to build crystal radios. The original crystal radio builders used high impedance headphones. In modern builds, you are as likely to include a powered amplifier to drive a speaker or normal headphones (which are usually around 4 to 16 ohms).

[George] builds his own speakers using chile cans, some wire, a few magnets, part of a Pepsi can (we are pretty sure someone will leave a comment that Coke cans sound better), and the iron core out of an audio transformer. You can see a very detailed video of the process, below.

There is a little woodworking …read more

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Wilderness Radio Build

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[AA7EE] is no stranger to building radios. His latest is a from-scratch build of a 20 meter QRP transceiver based on the popular SST design. Although the SST has been available as a kit, [AA7EE] incorporated some design changes from others and some of his own, too. He even added an onboard keyer to simplify operation. You can see videos of the radio below.

The build uses Manhattan-style PCB pads. Although the construction is very attractive, the real value of the post is the detailed explanation of not only how, but why everything is the way it is. This isn’t …read more

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High Performance Crystal Radio

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When you think of a crystal radio, you probably think of something simple maybe built out of household scraps. Not if you are [Chris Wendling]. He recently posted a video (see below) of his high-performance crystal set. He doesn’t take any shortcuts: he has several hundred feet of antenna wire, and uses a cold-water pipe ground system. With no amplifier, a strong signal input is crucial.

The radio has four subsystems: an antenna tuner, a bandpass filter, a detector, and a powered audio output system. He also has a truly enormous system of speakers on the ceiling–this isn’t the crystal …read more

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Raspberry Pi Radio Streaming Service Guts Yamaha Shelf System

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There are dozens — dozens! — of options to meet your music and streaming needs these days.  Looking to make something of his own that retains that 90’s vibe of having a dedicated stereo system but with modern wireless integration, [thk4711] turned an old Yamaha hifi into a Raspberry Pi streaming client.

As far as the case goes, a few modifications allowed [thk4711] to use all of the existing buttons, and a quick-swap of the back-plate and screen gave him a better enclosure than one he could fabricate himself. The power supply proved to be the most difficult part of …read more

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Tracking Airplanes From An Autonomous Boat

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Airplane tracking systems like FlightRadar24 rely on people running radios that receive the ADS-B signal and forward the data on to them. That doesn’t work so well in the middle of the ocean, though: in spots like the mid-Atlantic, there are no islands to speak of.

So, the service is now experimenting with a new approach: putting an ADS-B radio onto an autonomous boat. The boat is a Wave Glider from Liquid Robotics, an autonomous boat that harvests the power of the waves to run propulsion, guidance, and its payload. In this case, that payload includes an ADS-B receiver and …read more

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Make Your Own Simple VHF Tuning Capacitor

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If you enjoy building radio projects you may have noticed something slightly worrying over the last few years in your component supply. Variable capacitors are no longer as plentiful as they used to be. There was a time when all radio receivers contained at least one, now with the advent of the varicap diode and the frequency synthesiser the traditional tuning capacitor is a rare breed. They are still made, but they’re not cheap and they won’t appear so readily in your junk box any more.

Fortunately a variable capacitor is a surprisingly simple device, and one you can make …read more

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Build a Tiny (Unstable) Bugging Device

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We don’t know who the [amgworkshop] wanted to listen in on, but they apparently went searching for a small FM wireless transmitter. There’s plenty of circuits around, but they wanted something smaller. The original circuit had a variable capacitor to tune the output frequency. The new design uses a fixed capacitor and a spring for an antenna. You can see the build steps in the video below, but don’t expect a lot of frequency stability or fidelity out of a single transistor transmitter.

The parts list is minimal. In addition to a coin cell holder (which serves as the construction …read more

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Police Baffled? Send For The Radio Amateurs!

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The police force in Evanston, Illinois had a problem on their hands. A mystery transmitter was blocking legal use of radio devices, car key fobs, cellphones, and other transmitters in an area of their city, and since it was also blocking 911 calls they decided to investigate it. Their first call for help went to the FCC who weren’t much use, telling them to talk to the manufacturers of the devices affected.

Eventually they approached the ARRL, the USA’s national amateur radio organisation, who sent along [Kermit Carlson, W9XA] to investigate. He fairly quickly identified the frequencies with the strongest …read more

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Google Unveils Their Experimental Plan For Wireless Broadband Service

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Two years ago, the FCC, with interested parties in Microsoft, Google, and many startups, created the Citizens Band Radio Service (CBRS), a rule that would open up the 3550-3650 MHz band  to anyone, or any company, to create their own wireless backbone between WiFi access points. It is the wireless solution to the last-mile problem, and last year the FCC enthusiastically endorsed the creation of the CBRS.

In a recently released FCC filing, Google has announced their experimental protocol for testing the new CBRS. This isn’t fast Internet to a lamp pole on the corner of the street yet, but …read more

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Secret Riddle Retro Radio

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When [the-rene] was building an escape room, he decided to have a clue delivered by radio. Well, not exactly radio, but rather an old-fashioned radio that lets you tune to a faux radio station that asks a riddle. When you solve the riddle, a secret compartment opens up. [the-rene] says you could have the compartment contain a key or a clue or even a cookie.

The outer case is actually an old radio gutted for this purpose. In addition, a laser cut box and a servo motor form the secret compartment.

The inside of the radio is decidedly modern. A …read more

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