Building a crystal radio isn’t exactly rocket science. Some people who build them go for pushing them technically as far as they can go. Others, like [Billy Cheung], go for style points. The modular radio and phone speaker looks like it came out of the movie Brazil. The metallic gramophone-like speaker horn adds to the appeal and mechanically amplifies the sound, too.
The video (see below) isn’t exactly a how-to, but if you watch to the end there is enough information that you could probably reproduce something at least similar. There are actually several horns. One is made from copper, another from paper, and one from a plastic bottle.
Continue reading “Radio and Phone Speaker has Style”
You have a shoe box sized computer that you want to use in a Mars fly by. How do you communicate with it? The answer is a very clever set of antennas. I got to sit down with Nacer Chahat, one of the engineers on the Jet Propulsion Laboratory team responsible for antenna design on Mars Cube One (MarCO). Two of these CubeSats that will soon be used to help a lander reach Mars. We talked about the work that went into MarCO, the deployable radar antenna he’s worked on for the RainCube project, and the early progress on OMERA, the One Meter Reflectarray.
This is a fascinating discussion of dealing with a multitude of engineering challenges including lack of available space for the antenna components, and power and weight limitations. Check out the video interview to see how the people at JPL fit it all into this, and other tiny satellites, then join us below for more details.
Continue reading “Interview: Nacer Chahat Designs Antennas for Mars CubeSats”
Star Trek has never let technology get in the way of a good story. Gene Roddenberry and the writers of the show thought up some amazing gadgets, from transporters to replicators to the warp core itself. Star Trek: The Next Generation brought us the iconic communicator badge. In 1987, a long-range radio device which could fit in a pin was science fiction. [Joe] is bringing these badges a bit closer to the real world with his entry in the 2017 Hackaday Sci-Fi Contest.
The first problem [Joe] dealt with was finding a radio which could run from watch batteries, and provide decently long-range operations. He chose the HopeRF RFM69HCW. Bringing fiction a bit closer to reality, this module has been used for orbital communications with low-cost satellites.
The Badge’s processor is a Teensy LC. [Joe] is rolling his own Teensy, which means using bootloader chips from PJRC, as well as the main microcontroller. Kicking the main micro into operation is where [Joe] is stuck right now. Somewhere between the breadboard and the first spin of the surface mount PCB things went a bit sideways. The oscillators are running, but there are no USB communications. [Joe] is trying another board spin. He made a few improvements and already has new boards on the way. Switching to a toaster oven or skillet paste and solder setup would definitely help him get the new badges up and running.
There is one man whose hour-long sessions in my company give me days of stress and worry. He can be found in a soundless and windowless room deep in the bowels of an anonymous building in a town on the outskirts of London. You’ve probably driven past it or others like it worldwide, without being aware of the sinister instruments that lie within.
The man in question is sometimes there to please the demands of the State, but there’s nothing too scary about him. Instead he’s an engineer and expert in electromagnetic compatibility, and the windowless room is a metal-walled and RF-proof EMC lab lined with ferrite tiles and conductive foam spikes. I’m there with the friend on whose work I lend a hand from time to time, and we’re about to discover whether all our efforts have been in vain as the piece of equipment over which we’ve toiled faces a battery of RF-related tests. As before when I’ve described working on products of this nature the specifics are subject to NDAs and in this case there is a strict no-cameras policy at the EMC lab, so yet again my apologies as any pictures and specifics will be generic.
There are two broadly different sets of tests which our equipment will face: RF radiation, and RF injection. In simple terms: what RF does it emit, and what happens when you push RF into it through its connectors and cables? We’ll look at each in turn as a broad overview pitched at those who’ve never seen inside an EMC lab, sadly there simply isn’t enough space in a Hackaday article to cover every nuance.
Continue reading “An Overview Of The Dreaded EMC Tests”
News comes to us this week that the famous HAARP antenna array is to be brought back into service for experiments by the University of Alaska. Built in the 1990s for the US Air Force’s High Frequency Active Auroral Research Program, the array is a 40-acre site containing a phased array of 180 HF antennas and their associated high power transmitters. Its purpose it to conduct research on charged particles in the upper atmosphere, but that hasn’t stopped an array of bizarre conspiracy theories being built around its existence.
The Air Force gave up the site to the university a few years ago, and it is their work that is about to recommence. They will be looking at the effects of charged particles on satellite-to-ground communications, as well as over-the-horizon communications and visible observations of the resulting airglow. If you live in Alaska you may be able to see the experiments in your skies, but residents elsewhere should be able to follow them with an HF radio. It’s even reported that they are seeking reports from SWLs (Short Wave Listeners). Frequencies and times will be announced on the @UAFGI Twitter account. Perhaps canny radio amateurs will join in the fun, after all it’s not often that the exact time and place of an aurora is known in advance.
Tinfoil hat wearers will no doubt have many entertaining things to say about this event, but for the rest of us it’s an opportunity for a grandstand seat on some cutting-edge atmospheric research. We’ve reported in the past on another piece of upper atmosphere research, a plan to seed it with plasma from cubesats, and for those of you that follow our Retrotechtacular series we’ve also featured a vintage look at over-the-horizon radar.
HAARP antenna array picture: Michael Kleiman, US Air Force [Public domain], via Wikimedia Commons.
Morse code enthusiasts can be picky about their paddles. After all, they are the interface between the man and the machine, and experienced telegraphers can recognize each other by their “hands”. So even though [Edgar] started out on a cheap, clicky paddle, it wouldn’t be long before he made a better one of his own. And in the process, he also made what we think is probably the thinnest paddle out there, being a single sheet of FR4 PCB material and a button cell battery. This would be perfect for a pocketable QRP (low-power) rig. Check it out in action in the video below.
There’s not much to a Morse code paddle. It could, of course, be as simple as two switches — one for “dit” and one for “dah”. You could make one out of a paperclip. [Edgar]’s version replaces the switches with capacitive sensing, done by the ATtiny4 on board. Because this was an entry in the 1kB challenge, he prioritized code size over features, and got it down to a ridiculous 126 bytes! Even so, it has deluxe features like autorepeat. We’d have to dig into the code to see if it’s iambic.
Continue reading “World’s Thinnest Morse Code Touch Paddle”
We don’t think [VK4FFAB] did himself a favor by calling his seven-part LTSpice tutorial LTSpice for Radio Amateurs. Sure, the posts do focus on radio frequency analysis, but these days lots of people are involved in radio work that aren’t necessarily hams.
Either way, if you are interested in simulating RF amplifiers and filters, you ought to check these posts out. Of course, the first few cover simple things like voltage dividers just to get your feet wet. The final part even covers a double-balanced mixer with some transformers, so there’s quite a range of material.
Continue reading “LTSpice for Radio Amateurs (and Others)”