Toroid Transformers Explained

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.


Lezing over 3d printers op vrijdag 24 februari

Op vrijdag 24 februari gaf Jeffrey PD1NL samen met zijn zoon Joey een lezing en demonstratie over 3d printers. Allerlei facetten kwamen voorbij zoals materiaalkeuze, ontwerp, software, printers en natuurlijk een demonstratie.

Er kwamen opvallend veel amateurs naar deze bijeenkomst toe om een kijkje te nemen in het nieuwe lokaal en vooral om te leren van de presentatie en demonstratie.

Joey hield een korte presentatie over de 3D-printers, de materialen en de software die je kunt gebruiken. Alle vragen uit het aanwezige publiek werden snel en vakkundig beantwoord waarna Jeffrey overging tot de demonstratie.

Op de achtergrond liep al enige tijd een printer te snorren en onder de extruder (hier komt het gesmolten kunststof uit dat de print vormt) verscheen langzaam maar zeker een geel plastic bootje.

Er werd stevig gediscussieerd over de praktische toepassing en het nut van dit alles maar de voorbeelden die Jeffrey had meegenomen lieten zien dat er voor de knutselende amateur wel degelijk een praktische toepassing was.

Over het te gebruiken materiaal werd nog lang nagepraat en er werden links en rechts wat ervaringen van andere amateurs uitgewisseld. Al met al werd het een zeer gezellige én leerzame avond.

Jeffrey en Joey, bedankt voor jullie bijdrage op deze vrijdagavond!

Wil je nou ook eens komen kijken naar wat andere amateurs hebben gemaakt of waar ze mee bezig zijn? Of wil je zelf een keer trots laten zien wat je hebt geknutseld? Heb je misschien een praktische vraag die de mening en ervaring van andere amateurs benodigt? Kom dan op vrijdag naar de verenigingsavond van de VRZA in het clublokaal aan de Dennestraat 2 in Hoensbroek-Heerlen. Vanaf 20 uur ben je van harte welkom!

Silent key: PDØHCE – Huub Kuijen

Onlangs bereikte ons het droevige bericht dat PDØHCE (Huub Kuijen) op 69-jarige leeftijd is overleden.

Huub was de laatste jaren tijdelijk niet actief als amateur maar was van plan zijn hobby weer op te pakken. Helaas heeft het niet zo mogen zijn.

Namens alle leden van de VRZA Zuid-Limburg wenst het bestuur de familie van Huub heel veel sterkte toe.

NASA Help Wanted: Ham Radio Operators Please Apply

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.

Digital Library Of Amateur Radio And Communications Is A Treasure Trove

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.

The USAF (Almost) Declares War On Illinois Radio Amateurs

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.

De VRZA is verhuisd!

Op vrijdag 3 februari vond de eerste bijeenkomst plaats op de nieuwe locatie. Na even zoeken waar de ingang was en hoe je in de zaal kwam, hadden toch 12 leden de bijeenkomst gevonden, een mooie opkomst! Er werd klassiek geouwehoerd, zagen wat minder frequente bezoekers en zo werd het toch weer gezellig.

De QSL-kast komt ook weer op te hangen. Door wat logistieke uitdagingen is de kast wel op de nieuwe locatie aangekomen maar hangt ‘ie nog niet op, dat gaan we nog verzorgen. Dus je hoeft niet om je kaarten verlegen te zitten!

Het nieuwe adres is:

’t Volkshuis, Dennestraat 2 in Heerlen

Dus tot en met 23 januari ben je nog welkom in Treebeek!