Categorie: Hackaday

HF radios often use toroidal transformers and winding them is a rite of passage for many RF hackers. [David Casler, KE0OG] received a question about how they work and answered it in a recent video that you can see below.

Understanding how a conventional transformer works is reasonably simple, but toroids often seem mysterious because the thing that makes them beneficial is also what makes them confusing. The magnetic field for such a transformer is almost totally inside the “doughnut,” which means there is little interaction with the rest of the circuit, and the transformer can be very efficient.

The toroid itself is made of special material. They are usually formed from powdered iron oxide mixed with other metals such as cobalt, copper, nickel, manganese, and zinc bound with some sort of non-conducting binder like an epoxy. Ferrite cores have relatively low permeability, low saturation flux density, and low Curie temperature. The powder also reduces the generation of eddy currents, a source of loss in transformers. Their biggest advantage is their high electrical resistivity, which helps reduce the generation of eddy currents.

If you haven’t worked through how these common little transformers work, [David]’s talk should help you get a grip on them. These aren’t just for RF. You sometimes see them in power supplies that need to be efficient, too. If you are too lazy to wind your own, there’s always help.

NASA’s been recruiting citizen scientists lately, and their latest call is looking for help from ham radio operators. They want you to make and report radio contacts during the 2023 and 2024 North American eclipses. From their website:

Communication is possible due to interactions between our Sun and the ionosphere, the ionized region of the Earth’s atmosphere located roughly 80 to 1000 km overhead. The upcoming eclipses (October 14, 2023, and April 8, 2024) provide unique opportunities to study these interactions. As you and other HamSCI members transmit, receive, and record signals across the radio spectrum during the eclipse, you will create valuable data to test computer models of the ionosphere.

The upcoming eclipses are in October of this year and in April 2024, so you have some time to get your station in order. According to NASA, “It will be a fun, friendly event with a competitive element.” So if you like science, space, or contesting, it sounds like you’ll be interested. Right now, the big event is the Solar Eclipse QSO Party. There will also be a signal spotting challenge and some measurements of WWV, CHU, AM broadcast stations, and measurements of the ionosphere height. There will also be some sort of very low-frequency event. Details on many of these events are still pending.

Hams, of course, have a long history of experimenting with space. They routinely bounce signals off the moon. They also let radio signals bounce off the trails of ionized gas behind meteors using special computer programs.

Having a big bookshelf of ham radio books and magazines used to be a point of bragging right for hams. These days, you are more likely to just browse the internet for information. But you can still have, virtually, that big shelf of old ham books, thanks to the DLARC — the digital library of Amateur Radio and Communications.

A grant from a private foundation has enable the Internet Archive to scan and index a trove of ham radio publications, including the old Callbooks, 73 Magazine, several ham radio group’s newsletters from around the globe, Radio Craft, and manuals from Icom, Kenwood, Yaesu, and others.

There are some old QST magazines and the index to newer ones. You can find catalogs and military documents. We miss a lot of these old magazines and newsletters. For example, RCA’s “Ham Tips” is something you won’t find anything like anymore. Most of the material is in English, but there are some other languages represented. For example, the Dutch version of Popular Electronics is available. There’s also material in Afrikaans, Japanese, German, and Spanish.

Some of this is only of historical interest. But some of the RF and electronic design information in here is timeless. Also, if you want to find information about that boat anchor you bought at the garage sale, this isn’t a bad place to look for the original manuals. It reminded us, on a smaller scale, of the World Radio History site, where we often do research for Hackaday posts about things from the past.

Not a ham? Doesn’t matter. A lot of this information is interesting to anyone who wants to know more about electronics. Then again, why aren’t you? [Dan Maloney] can get you going for under $50. If you think of hams as old people banging on code keys, you might be surprised at what the modern ham station looks like.

Every week the Hackaday editors gather online to discuss the tech stories of the moment, and among the topics this week was the balloons shot down over North America that are thought to be Chinese spying devices. Among the banter came the amusing thought that enterprising trolls on the Pacific rim could launch balloons to keep the fearless defenders of American skies firing off missiles into the beyond.

But humor may have overshadowed by events, because it seems one of the craft they shot down was just that. It wasn’t a troll though, the evidence points to an amateur radio pico balloon — a helium-filled Mylar party balloon with a tiny solar-powered WSPR transmitter as its payload.

The balloon thought to have been shot down was launched by the Northern Illinois Bottlecap Balloon Brigade, a group of radio amateurs who launch small helium-filled Mylar balloons carrying the barest minimum for a solar-powered WSPR beacon. Its callsign was K9YO, and having circumnavigated the globe seven times since its launch on the 10th of October it was last seen off Alaska on February 11th. Its projected course and timing tallies with the craft reported shot down by the US Air Force, so it seems the military used hundreds of thousands of dollars-worth of high-tech weaponry to shoot down a few tens of dollars worth of hobby electronics they could have readily tracked online. We love the smell of napalm in the morning!

Their website has a host of technical information on the balloons and the beacons, providing a fascinating insight into this facet of amateur radio that is well worth a read in itself. The full technical details of the USAF missile system used to shoot them down, sadly remains classified.

There was a time when one of the perks of having a ham radio in your car (or on your belt) was you could make phone calls using a “phone patch.” In the 1970s, calling someone from inside your parked car turned heads. Now, of course,  it is an everyday occurrence thanks to cell phones. But in 1977, cell phones were nowhere to be found. Joseph Sugarman, the well-known founder of JS&A, saw a need and wanted to fill it. So he offered the “PocketCom CB” which was billed as the “world’s smallest citizens band transceiver.” You can see the full-page ad from 1977 below.

Remember that this is from an era when ICs that could operate at 30 MHz were not the norm, so you have to temper your expectations. The little unit was 5.5 in by 1.5 in and less than an inch thick. That’s actually not bad, but you had — optimistically — 100 mW of output power. They claimed the N cell batteries would last two weeks with average use, but we imagine a lot less as soon as you start transmitting. The weight was 5 oz, but we suspect that is without the batteries.

The device had a crystal for channel 14, and you could buy another crystal to get a second channel. Given that the unit was selling for about $40 to $20, it was telling that the extra crystal cost $8. We heard that over 250,000 of these were sold. The ad copy mentions they were used on the TV show Charlie’s Angels, but we can’t picture how that happened. It also mentioned it can be used as a pager, an intercom, a telephone, or a security device.

In operation, the devices were pretty simple. The 40″ antenna, when pulled out, would make the unit a bit more cumbersome. We found a relatively recent review on the CB Gazette from someone who picked up two of these on the used market. Seemed like they did work, although they were probably no better than a kid’s walkie-talkie.

Many hams convert CBs to the 10-meter band or even the 6-meter band, and we wonder if a crystal would pull these to 10 meters. Before cell phones, people thought we needed bigger towers, more power, and more channels. Turns out, it is just the opposite.

The Ham Radio All-in-one cable (AIOC) is a small PCB attachment for a popular series of radio transceivers which adds a USB-attached audio interface and virtual TTY port for programming and the push-to-talk function. The STM32F373 microcontroller (which, sadly is still hard to find in the usual channels) is a perfect fit for this application, with all the needed hardware resources.

With USB-C connectivity, the AIOC enumerates as ahttps://github.com/skuep/AIOC

” data-image-caption=”” data-medium-file=”https://hackaday.com/wp-content/uploads/2022/12/k1-aioc-photo.jpg?w=400″ data-large-file=”https://hackaday.com/wp-content/uploads/2022/12/k1-aioc-photo.jpg?w=537″ width=”400″ height=”326″> sound card as well as a virtual serial device, so interfacing to practically any host computer should be plug-and-play. Connection to the radio uses 12mm separation 3.5mm and 2.5mm TRS connectors, so is compatible with at least the Baofeng UV-5R but likely many other cheap transceivers that have the same physical setup.Instructions are provided to use the AIOC with Dire Wolf for easy access to APRS applications, which makes a nice out-of-the-box demo to get you going. APRS is not all about tracking things though since other applications can sit atop the APRS/AX.25 network, for example, HROT: the ham radio of things.

We’ve seen quite a few Baofeng (and related products) hacks, like this sketchy pile of wires allowing one to experiment with the guts of the radio for APRS. Of course, such cheap radio transceivers cut so many engineering corners that there are movements to ban their sale, so maybe a new batch of better radios from our friends in the East is on the horizon?

Thanks to [Hspil] for the tip!

Software-defined radio is all the rage these days, and for good reason. It eliminates or drastically reduces the amount of otherwise pricey equipment needed to transmit or even just receive, and can pack many more features than most affordable radio setups otherwise would have. It also makes it possible to go mobile much more easily. [Rostislav Persion] uses a laptop for on-the-go SDR activities, and designed this 3D printed antenna mount to make his radio adventures much easier.

The antenna mount is a small 3D printed enclosure for his NESDR Smart Dongle with a wide base to attach to the back of his laptop lid with Velcro so it can easily be removed or attached. This allows him to run a single USB cable to the dongle and have it oriented properly for maximum antenna effectiveness without something cumbersome like a dedicated antenna stand. [Rostislav] even modeled the entire assembly so that he could run a stress analysis on it, and from that data ended up filling it with epoxy to ensure maximum lifespan with minimal wear on the components.

We definitely appreciate the simple and clean build which allows easy access to HF and higher frequencies while mobile, especially since the 3D modeling takes it a step beyond simply printing a 3D accessory and hoping for the best. There’s even an improved version on his site here. To go even one step further, though, we’ve seen the antennas themselves get designed and then 3D printed directly.

In amateur radio circles, almost no single piece of equipment serves as more of a magnet for controversy than the humble Baofeng handheld transceiver. It’s understandable — the radio is a shining example of value engineering, with just enough parts to its job while staying just on the edge of FCC rules. And at about $25 a pop, the radios are cheap enough that experimentation is practically a requirement of ownership.

But stripped down as the Baofeng may be, it holds secrets inside that are even more tempting to play with than the radio itself. And who better than [HB9BLA], a guy who has a suspiciously familiar Swiss accent, to guide us through the RF module at the heart of the Baofeng, the SA818. For about $8 you can get one of these little marvels off AliExpress and have nearly all the important parts of a VHF or UHF radio — an SDR transceiver, a power amp, and all the glue logic to make it work.

In the video below, [Andreas] puts the SA818 module through its paces with the help of a board that pairs the module with a few accessories, like an audio amp and a low-pass RF filter. With a Raspberry Pi and a Python library to control the module, it’s a decent imitation of the functionality of a Baofeng. But that’s only the beginning. By adding a USB sound card to the Pi, the setup was able to get into every ham’s favorite packet radio system, APRS. There are a ton of other applications for the SA818 modules, some of which [Andreas] mentions at the end of the video. Pocket-sized repeaters, a ridiculously small EchoLink hotspot, and even an AllStar node in an Altoids tin.

Of course, if you want to get in on the fun, you’re going to need an amateur radio license. Don’t worry, it’s easy — we’ll help you get there.

For years the Internet Archive has provided the online community with a breathtaking collection of resources, out of print books, magazines, recordings, software, and any other imaginable digital asset in easily retrievable form. Now with the help of a grant from the Amateur Radio Digital Communications Foundation they are seeking to create a collection that documents amateur radio from its earliest days to the present.

The work will be multi-faceted, and include the print and digital materials we’d expect, as well as personal archives and oral histories from notable radio amateurs. For many of us this will provide a wealth of technical details and insights into taming the ionosphere, but for future historians it will be an invaluable reference on the first century of the hobby.

Amateur radio is perhaps the oldest hardware hacking pursuit of the electronic age, because certainly at the start, radio was electronics. Thus amateur radio’s long history has indirectly given us many of the things we take for granted today. Sure it has its moribund aspects, but we think if it continues to follow the growth of new technology as it has for so many years it will continue to be an exciting pursuit. We look forward to browsing this archive, and we hope to see it grow over the years.

Header image: Lescarboura, Austin C. (Austin Celestin), 1891-, No restrictions.