Many thanks to SWLing Post contributor, Paul Evans, who shares the following video and article via Hackaday:
There’s been a spate of apocalypse related articles over the last few weeks, but when I saw an AM radio made from a hand-wound coil and an oxidized British penny, I couldn’t help but be impressed. We’ve covered foxhole radios, stereotypical radios that are cobbled together from found parts during wartime.
This example uses a variable capacitor for tuning, but that’s technically optional. All that’s really needed is a coil and something to work as a diode. Surprisingly, copper oxide is a semiconductor, and the surface oxidation on a penny is enough to form a rudimentary diode.[…]
Click here to read the full article at Hackaday.
Thanks for sharing this, Paul. I absolutely love simple receivers like this one. In the past, I’ve built several crystal radios and had great success hearing local AM broadcasters. Indeed, the very first kit I ever built was a crystal radio, then later a foxhole style receiver.
Post readers: Have you ever built a radio similar to this one that uses an oxidized penny? Please comment!
Click here to read posts from our archives that focus on crystal radios.
Many thanks to SWLing Post contributor, Paul Evans (W4/VP9KF), who shares the following article from Hackaday:
Before swearing my fealty to the Jolly Wrencher, I wrote for several other sites, creating more or less the same sort of content I do now. In fact, the topical overlap was enough that occasionally those articles would get picked up here on Hackaday. One of those articles, which graced the pages of this site a little more than seven years ago, was Getting Started with RTL-SDR. The original linked article has long since disappeared, and the site it was hosted on is now apparently dedicated to Nintendo games, but you can probably get the gist of what it was about from the title alone.
When I wrote that article in 2012, the RTL-SDR project and its community were still in their infancy. It took some real digging to find out which TV tuners based on the Realtek RTL2832U were supported, what adapters you needed to connect more capable antennas, and how to compile all the software necessary to get them listening outside of their advertised frequency range. It wasn’t exactly the most user-friendly experience, and when it was all said and done, you were left largely to your own devices. If you didn’t know how to create your own receivers in GNU Radio, there wasn’t a whole lot you could do other than eavesdrop on hams or tune into local FM broadcasts.
Nearly a decade later, things have changed dramatically. The RTL-SDR hardware and software has itself improved enormously, but perhaps more importantly, the success of the project has kicked off something of a revolution in the software defined radio (SDR) world. Prior to 2012, SDRs were certainly not unobtainable, but they were considerably more expensive. Back then, the most comparable device on the market would have been the FUNcube dongle, a nearly $200 USD receiver that was actually designed for receiving data from CubeSats. Anything cheaper than that was likely to be a kit, and often operated within a narrower range of frequencies.
Today, we would argue that an RTL-SDR receiver is a must-have tool.[…]
Click here to continue reading the full article at the excellent Hackaday blog.
Of course, for all things RTL-SDR and beyond, I highly recommend bookmarking RTL-SDR.com.
The RTL-SDR.com blog also manufactures my favorite flavor of the RTL-SDR dongle along with a nice bundle of antennas. Click here to check it out on Amazon.com (this affiliate link supports the SWLing Post).
Wow! Thank you, Hackaday:
HOPE XII: TIME TRAVEL WITH SOFTWARE DEFINED RADIO
by: Tom Nardi
It’s easy to dismiss radio as little more than background noise while we drive. At worst you might even think it’s just another method for advertisers to peddle their wares. But in reality it’s a snapshot of the culture of a particular time and place; a record of what was in the news, what music was popular, what the weather was like, basically what life was like. If it was important enough to be worth the expense and complexity of broadcasting it on the radio, it’s probably worth keeping for future reference.
But radio is fleeting, a 24/7 stream of content that’s never exactly the same twice. Yet while we obsessively document music and video, nobody’s bothering to record radio. You can easily hop online and watch a TV show that originally aired 50 years ago, but good luck finding a recording of what your local radio station was broadcasting last week. All that information, that rich tapestry of life, is gone and there’s nothing we can do about it.
Or can we? At HOPE XII, Thomas Witherspoon gave a talk called “Creating a Radio Time Machine: Software-Defined Radios and Time-Shifted Recordings”, an overview of the work he’s been doing recording and cataloging the broadcast radio spectrum. He demonstrated how anyone can use low cost SDR hardware to record, and later play back, whole chunks of the AM and shortwave bands. Rather than an audio file containing a single radio station, the method he describes allows you to interactively tune in to different stations and explore the airwaves as if it were live.[…]
Continue reading the full article at Hackaday.
(Source: Hackaday via bernieS)
Unless you live in a cave, you’ve probably heard a little about the thirteen people — mostly children — trapped in the Tham Luang Nang Non cave in Thailand. What you may have missed, though, is the hacker/ham radio connection. The British Cave Rescue Council (BCRC) was asked for their expert help. [Rick Stanton], [John Volanthen] and [Rob Harper] answered the call. They were equipped with HeyPhones. The HeyPhone is a 17-year-old design from [John Hey, G3TDZ]. Sadly, [G3TDZ] is now a silent key (ham radio parlance for deceased) so he didn’t get to see his design play a role in this high-profile rescue, although it has apparently been a part of many others in the past.
The HeyPhone is actually considered obsolete but is still in service with some teams. The radio uses USB (upper sideband, not universal serial bus) at 87 kHz. The low frequency can penetrate deep into the ground using either induction loop antennas like the older Molephone, or — more commonly — with electrodes injecting RF energy directly into the ground.
You can find a very detailed article about the radio from 2001 if you want more details. The system is somewhat dated, but apparently works well and that’s what counts.[…]
Click here to read the full article at Hackaday.
Many thanks to SWLing Post contributor, Dan Robinson, for sharing the following story:
[…]In a publication released last week, Google asked the FCC to treat some information relating to radio experiments as confidential. These experiments involve highly directional and therefore high power [96.4 kilowatt] transmissions at 2.5 GHz, 5.8GHz, 24GHz, 71-76GHz, and 81-86GHz. These experiments will take place at Spaceport America, a 12,000 foot runway in the middle of New Mexico occasionally used by SpaceX, Virgin Galactic, and now Google.
For the most part, this document only tells the FCC that Google won’t be causing harmful interference in their radio experiments. There few other details, save for what bands and transmitters Google will be using and an experimental radio license call sign (WI9XZE) that doesn’t show up in the FCC database.[…]
Read the full article at Hackaday…
Click here to read FCC File No. 0142-EX-PL-2016 (Google Public Redacted Version).
Jagadish Chandra Bose in Royal Institution, London
Many thanks to SWLing Post reader, A Black, for sharing the following article from the excellent Hackaday blog:
J.C. BOSE AND THE INVENTION OF RADIO
The early days of electricity appear to have been a cutthroat time. While academics were busy uncovering the mysteries of electromagnetism, bands of entrepreneurs were waiting to pounce on the pure science and engineer solutions to problems that didn’t even exist yet, but could no doubt turn into profitable ventures. We’ve all heard of the epic battles between Edison and Tesla and Westinghouse, and even with the benefit of more than a century of hindsight it’s hard to tell who did what to whom. But another conflict was brewing at the turn of 19th century, this time between an Indian polymath and an Italian nobleman, and it would determine who got credit for laying the foundations for the key technology of the 20th century – radio.
Appointment and Disappointment
In 1885, a 27-year old Jagadish Chandra Bose returned to his native India from England, where he had been studying natural science at Cambridge. Originally sent there to study medicine, Bose had withdrawn due to ill-health exacerbated by the disagreeable aroma of the dissection rooms. Instead, Bose returned with a collection of degrees in multiple disciplines and a letter of introduction that prompted the Viceroy of India to request an appointment for him at Presidency College in Kolkata (Calcutta). One did not refuse a viceroy’s request, and despite protests by the college administration, Bose was appointed professor of physics.
Click here to continue reading on Hackaday…