If you want to really understand a technology, and if you’re like us, you’ll need to re-build it yourself. It’s one thing to say that you understand (analog) broadcast TV by reading up on Wikipedia, or even by looking at scope traces. But when you’ve written a flow graph that successfully transmits a test image to a normal TV using just a software-defined radio, you can pretty easily say that you’ve mastered the topic.
[Marble] wrote his flow for PAL, but it should be fairly easy to modify it to work with NTSC if you’re living in the US or Japan. Sending black and white is “easy” but to transmit a full color image, you’ll need to read up on color spaces. Check out [marble]’s project log.
Hackaday has another hacker who’s interested in broadcasting to dinosaur TVs: [CNLohr]. Check out his virtuoso builds for the ATtiny and for the ESP8266.
(Yes, the headline image is
one of his earlier trials with black and white from Wikipedia — we just like the look.)
Students from the Indian Institute of Science Education and Research combined a commercial satellite dish, a satellite finder and an Arduino, and produced a workable radio telescope. The satellite dish provides the LNB (low noise block) and the associated set-top box is used only for power. Their LNB employs an aluminum foil shield to block extraneous signals.
In addition to the hardware, the team built Python software to analyze the data and show several practical applications. They used known geostationary satellites to calibrate the signal from the finder (digitized by the Arduino) to determine power per unit voltage. They also calculated the beam width (about 3.4 degrees) and used the sun for other calibration steps.
Continue reading “Listen to the Sun, Saturn, and the Milky Way with Your Own Radio Telescope”
Most new houses are part of homeowners associations, covenants, or have other restrictions on the deed that dictate what color you can paint your house, the front door, or what type of mailbox is acceptable. For amateur radio operators, that means neighbors have the legal means to remove radio antennas, whether they’re unobtrusive 2 meter whips or gigantic moon bounce arrays. Antennas are ugly, HOAs claim, and drive down property values. Thousands of amateur radio operators have been silenced on the airwaves, simply because neighbors don’t like ugly antennas.
Now, this is about to change. The US House recently passed the Amateur Radio Parity Act (H.R. 1301) to amend the FCC’s Part 97 rules of amateur stations and private land-use restrictions.
The proposed amendment provides, ““Community associations should fairly administer private land-use regulations in the interest of their communities, while nevertheless permitting the installation and maintenance of effective outdoor Amateur Radio antennas.” This does not guarantee all antennas are allowed in communities governed by an HOA; the bill simply provides that antennas, ‘consistent with the aesthetic and physical characteristics of land and structures in community associations’ may be accommodated. While very few communities would allow a gigantic towers, C-band dishes, or 160 meters of coax strung up between trees, this bill will provide for small dipoles and inconspicuous antennae.
The full text of H.R. 1301 can be viewed on the ARRL site. The next step towards making this bill law is passage through the senate, and as always, visiting, calling, mailing, faxing, and emailing your senators (in that order) is the most effective way to make views heard.
At some point you’ve decided that you’re going to sell your wireless product (or any product with a clock that operates above 8kHz) in the United States. Good luck! You’re going to have to go through the FCC to get listed on the FCC OET EAS (Office of Engineering and Technology, Equipment Authorization System). Well… maybe.
As with everything FCC related, it’s very complicated, there are TLAs and confusing terms everywhere, and it will take you a lot longer than you’d like to figure out what it means for you. Whether you suffer through this, breeze by without a hitch, or never plan to subject yourself to this process, the FCC dance is an entertaining story so let’s dive in!
Continue reading “Preparing Your Product For The FCC”
[VK2ZAY] has a thing for 555 chips. Before the ready availability of microcontrollers, the 555 was the hardware hacker’s swiss army knife. After all, even though the chip is supposed to be a timer, it is really a bunch of simple pieces you can use to make a timer: a pair of comparators, a few transistors, and a flip-flop. You can use those parts in many different ways, and a timer is just one of them.
[VK2ZAY] used one as a key component in a simple spectrum analyzer. The 555 generates a ramp voltage which alters the frequency of an oscillator. The oscillator mixes with the input signal and a fixed-frequency superregenerative detector creates an output voltage proportional to the input signal strength. You can see a video of the whole setup, below.
Continue reading “Spectrum Analyzer With 555 Fits In A Tin”
[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 and hot gluing involved. The result is decidedly homemade looking, but if you want to say you built it yourself (or, if you are a prepper trying to get ready to rebuild after the apocalypse and you can’t find a cache of headphones) this might be just the ticket.
Most of the headphone hacks we see start with a pair of headphones. That’s a bit tautological, but the goal is usually to add features, not make the whole thing. It does give you some hacker cred, though, to be able to look at the other guy’s radio and say, “Oh. I see you used commercial headphones.”
Continue reading “High Impedance Headphones? They’re In The Can!”
[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 a simple project, and being able to see it completed step-by-step is very educational. About the only decision not adequately explained was the change of red and yellow knobs to black! You can see both versions in the videos below.
The Manhattan construction is tidy, but the radio also has an attractive case. The size is just big enough to stack a pair of paddles on top.
There may be some more enhancements for the little radio coming. We’ve covered [AA7EE’s] RF exploits before, including a physically attractive radios and details about the same construction method used in this radio.
Continue reading “Wilderness Radio Build”