Radio Hacks

1321 Articles

A Modern Take On A Piece Of Old Test Equipment

December 15, 2019 by No comments

The HP 11947A is something of a footnote in the back catalogue of Hewlett Packard test equipment. An attenuator and limiter with a bandwidth in the megahertz rather than the gigahertz. It’s possible that few laboratories have much use for one in 2019, but it does have one useful property: a full set of schematics and technical documentation. [James Wilson] chose the device as the subject of a clone using surface mount devices.

The result is very satisfyingly within spec, and he’s run a battery of tests to prove it. As he says, the HP design is a good one to start with.   As a device containing only passive components and with a maximum frequency in the VHF range this is a project that makes a very good design exercise for anyone interested in RF work or even who wishes to learn a bit of RF layout. At these frequencies there are still a significant number of layout factors that can affect performance, but the effect of conductor length and  stray capacitance is less than the much higher frequencies typically used by wireless-enabled microcontrollers.

WWII Aircraft Radio Roars To Life: What It Takes To Restore A Piece Of History

December 12, 2019 by 59 Comments

I’ve been told all my life about old-timey Army/Navy surplus stores where you could buy buckets of FT-243 crystals, radio gear, gas masks, and even a Jeep boxed-up in a big wooden crate. Sadly this is no longer the case. Today surplus stores only have contemporary Chinese-made boots, camping gear, and flashlights. They are bitterly disappointing except for one surplus store that I found while on vacation in the Adirondacks: Patriot of Lake George.

There I found a unicorn of historical significance; an un-modified-since-WW2 surplus CBY-46104 receiver with dynamotor. The date of manufacture was early-war, February 1942. This thing was preserved as good as the day it was removed from its F4F Hellcat. No ham has ever laid a soldering iron or a drill bit to it. Could this unit have seen some action in the south Pacific? Imagine the stories it could tell!

My unconventional restoration of this radio followed strict rules so as to minimize the evidence of repair both inside and out yet make this radio perform again as though it came fresh off the assembly line. Let’s see how I did.

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Restoring A 1949 Golden Throat Radio

December 9, 2019 by 14 Comments

[Mr. Carlson] has a really beautiful old 1949-era radio to restore and you can watch him do it in a comprehensive video, below. We aren’t sure what we were more amused by: the odd speaker that looks like a ceiling air vent or the sticker on the back certifying that the radio produces the tone of the “golden throat” signed by RCA’s chief engineer.

Electrically, the radio didn’t look that remarkable. Of course, the capacitors were presumed bad and replaced. The video made us remember how much we hated restringing dial radios!

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Hackaday Superconference: An Analog Engineer Dives Into RF

December 9, 2019 by 6 Comments

Those of us who work with electronics will usually come to the art through a particular avenue that we master while imbibing what we need from those around it. For example, an interest in audio circuitry may branch into DSP and microcontrollers as projects become more complex. Some realms though retain an aura of impossibility, a reputation as a Dark Art, and chief among them for many people is radio frequency (RF). Radio circuitry is often surprisingly simple, yet that simplicity conceals a wealth of complexity because the medium does not behave in the orderly manner of a relatively static analogue voltage or a set of low-frequency logic levels.

Chris Gammell is a familiar face to many Hackaday readers for his mastery of much electronic trickery, so it comes as something of a surprise to find that RF has been one of the gaps in his knowledge. In his talk at the Hackaday Superconference he took us through his journey into RF work, and the result is a must-watch for anyone with a curiosity about radio circuitry who didn’t know where to start.

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Zombies Ate Your Neighbors? Tell Everyone Through LoRa!

December 4, 2019 by 24 Comments

As popular as the post-apocalyptic Zombie genre is, there is a quite unrealistic component to most of the stories. Well, apart from the whole “the undead roaming the Earth” thing. But where are the nerds, and where is all the apocalypse-proof, solar-powered tech? Or is it exactly this lack of tech in those stories that serves as incentive to build it in the first place? Well, maybe it doesn’t have to be the end of the world to seek for ways to cope with a collapse of our modern communication infrastructure either. Just think of natural disasters — an earthquake or hurricane causing a long-term power outage for example. The folks at [sudomesh] tackle exactly this concern with their fully open source, off-grid, solar-powered, LoRa mesh network, Disaster Radio.

The network itself is built from single nodes comprising of a battery-backed solar panel, a LoRa module, and either the ESP8266 or ESP32 for WiFi connectivity. The idea is to connect to the network with your mobile phone through WiFi, therefore eliminating any need for additional components to actually use the network, and have the nodes communicate with each other via LoRa. Admittedly, LoRa may not be your best choice for high data rates, but it is a good choice for long-range communication when cellular networks aren’t an option. And while you can built it all by yourself with everything available on [sudomesh]’s GitHub page, a TTGO ESP32 LoRa module will do as well.

If the idea itself sounds familiar, we did indeed cover similar projects like HELPER and Skrypt earlier this year, showing that LoRa really seems to be a popular go-to for off-grid communication. But well, whether we really care about modern communication and helping each other out when all hell breaks loose instead of just primevally defending our own lives is of course another question.

Hacking Transmitters, 1920s Style

November 28, 2019 by 9 Comments

The origin of the term “breadboard” comes from an amusing past when wooden bread boards were swiped from kitchens and used as a canvas for radio hobbyists to roll homemade capacitors, inductors, and switches. At a period when commercial electronic components were limited, anything within reach was fair game.

[Andy Flowers], call sign K0SM, recently recreated some early transmitters using the same resources and techniques from the 1920s for the Bruce Kelley 1929 QSO Party. The style of the transmitters are based on [Ralph Hartley]’s oscillator circuit built for Bell Telephone in 1915. Most of the components he uses are from the time period, and one of the tubes he uses is even one of four tubes from the first Transatlantic contact in 1923.

Apart from vacuum tubes (which could be purchased) and meters (which could be scrounged from automobiles) [Flowers] recreated his own ferrite plate and outlet condensers for tuning the antennas. The spiderweb coils may not be as common today, but can be found in older Crosley receivers and use less wire than comparable cylindrical coils.

A number of others features of the transmitters also evoke period nostalgia. The coupling to the antenna can be changed using movable glass rods, although without shielding there are quite a number of factors to account for. A vertical panel in the 1920s style also shows measurements from the filament, plate current, and antenna coupling.

While amature radio has become increasingly high-tech over the last few years, it’s always good to see dedicated individuals keeping the old ways alive; no matter what kind of technology they’re interested in.

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Incredibly Tiny RF Antennas For Practical Nanotech Radios

November 25, 2019 by 18 Comments

Researchers may have created the smallest-ever radio-frequency antennas, a development that should be of interest to any nanotechnology enthusiasts. A group of scientists from Korea published a paper in ACS Nano that details the fabrication of a two-dimensional radio-frequency antenna for wearable applications. Most antennas made from metallic materials like aluminum, cooper, or steel which are too thick to use for nanotechnology applications, even in the wearables space. The newly created antenna instead uses metallic niobium diselenide (NbSe2) to create a monopole patch RF antenna. Even with its sub-micrometer thickness (less than 1/100 the width of a strand of human hair), it functions effectively.

The metallic niobium atoms are sandwiched between two layers of selenium atoms to create the incredibly thin 2D composition. This was accomplished by spray-coating layers of the NbSe2 nanosheets onto a plastic substrate. A 10 mm x 10 mm patch of the material was able to perform with a 70.6% radiation efficiency, propagating RF signals in all directions. Changing the length of the antenna allowed its frequency to be tuned from 2.01-2.80 GHz, which includes the range required for Bluetooth and WiFi connectivity.

Within the ever-shrinking realm of sensors for wearable technologies, there is sure to be a place for tiny antennas as well.

[Thanks Qes for the tip!]