Advies bij contact met amateurs uit Oekraïne

Internationale organisaties adviseren radiozendamateurs om bij contact met een Oekraïense amateur de roepletters, naam, QTH en andere persoonlijke details NIET te herhalen. Het is ook zeker NIET de bedoeling om contacten op het DX-cluster te zetten, of andere loggings te maken.

Dit alles om de veiligheid van deze amateurs te garanderen zodat zij niet kunnen worden achterhaald bij het maken van internationale contacten.

Bovenstaande is overigens volledig compliant met de machtigingsvoorwaarden in Nederland (je hoeft alleen je eigen roepletters te vermelden).

Wind-Up Tape Measure Transformed Into Portable Ham Antenna

If there’s one thing that amateur radio operators are good at, it’s turning just about anything into an antenna. And hams have a long history of portable operations, too, where they drag a (sometimes) minimalist setup of gear into the woods and set up shop to bag some contacts. Getting the two together, as with this field-portable antenna made from a tape measure, is a double win in any ham’s book.

For [Paul (OM0ET)], this build seems motivated mainly by the portability aspect, and less by the “will it antenna?” challenge. In keeping with that, he chose a 50-meter steel tape measure as the basis of the build. This isn’t one of those retractable tape measures, mind you — just a long strip of flexible metal on a wind-up spool in a plastic case. His idea was to use the tape as the radiator for an end-fed halfwave, or EFHW, antenna, a multiband design that’s a popular option for hams operating from the 80-m band down to the 10-m band. EFHW antennas require an impedance-matching transformer, a miniature version of which [Paul] built and tucked within the tape measure case, along with a BNC connector to connect to the radio and a flying lead to connect to the tape.

Since a half-wave antenna is half the length of the target wavelength, [Paul] cut off the last ten meters of the tape to save a little weight. He also scratched off the coating on the tape at about the 40-meter mark, to make good contact with the alligator clip on the flying lead. The first video below details the build, while the second video shows the antenna under test in the field, where it met all of the initial criteria of portability and ease of deployment.


Commodore Promotional Film From 1984 Enhanced

Over on Retro Recipe’s YouTube channel, [Perifractic] has been busy restoring an old promotional video of how Commodore computers were made back in 1984 (video below the break). He cleaned up the old VHS-quality version that’s been around for years, translated the German to English, and trimmed some bits here and there. The result is a fascinating look into the MOS factory, Commodore’s German factory, and a few other facilities around the globe. The film shows the chip design engineers in action, wafer manufacturing, chip dicing, and some serious micro-probing of bare die. We also see PCB production, and final assembly, test and burn-in of Commodore PET and C64s in Germany.

Check out the video description, where [Perifractic] goes over the processes he used to clean up video and audio using machine learning. If restoration interests you, check out the piece we wrote about these techniques to restore old photographs last year. Are there any similar factory tour films, restored or not, lurking around the web? Let us know in the comments below.



De bijeenkomsten van de afdeling 23 van de VRZA gaan weer door!

Vanaf maandag 31 januari gaan de bijeenkomsten van de VRZA Zuid-Limburg weer door! U bent van 20 tot uiterlijk 22 uur van harte welkom in het clublokaal.

Let op: de momenteel geldende coronamaatregelen zijn van kracht: mondkapje tijdens het rondlopen en 1,5m afstand.

Een corona toegangsbewijs is NIET nodig. Om discussie te voorkomen hierbij de tekst van de Rijksoverheid:

U heeft ook geen coronatoegangsbewijs nodig:

  • bij evenementen die normaal gesproken worden georganiseerd in bibliotheken en buurt- of wijkcentra. Zoals de wekelijkse bingo. Zolang de maaltijd maar niet centraal staat tijdens de activiteit;

A Simple EMF Detector And Electroscope You Can Make From Junk Box Parts ” data-image-caption=”” data-medium-file=”″ data-large-file=”″ width=”400″ height=”242″>
2N2222 devices used, but practically any junkbox NPN will do

Electromagnetic fields are everywhere, all around us. Some are generated naturally, but in vast majority of cases, it’s we humans that are generating them with artificial, electronic means. Everything from your mobile phone to the toaster will emit some sort of signal, be it intentional or not. So we think it only befits the general electronics-orientated hacker to have some way of sniffing around for these signals, so here is [Mirko Pavleski] with his take on a very simple pair of instruments to detect both static and dynamic electromagnetic fields. ” data-image-caption=”” data-medium-file=”″ data-large-file=”″ width=”400″ height=”347″>
CMOS clock input connected directly to the antenna. Warning! ESD damage risk!

The first unit (a simple electroscope) uses a cascade of 2N2222 NPN bipolar transistors configured to give a high current gain, so any charge near the antenna will result in increasing currents in subsequent stages, finally illuminating the LED. Simple stuff.

The second unit relies on the extremely high input impedance of the old-school CMOS 4017 decade counter, which is likely of the order of 100 MΩ or even more. Normally you would not leave such a CMOS input floating, or even connect it with too long a PCB trace — lest it pick up a stray signal —but for detecting alternating EM fields, this appears to work just fine. Configured as a simple divide-by-ten, when presenting 50 Hz AC, the LED can be seen to flash at 5 Hz.

Simple stuff, and this scribe has all those exact parts in the junk box, so will be constructing these shortly!

We’ve covered electroscopes for years, here’s a modern twist on a famous classic experiment, and some hair-raising experiments to get you started.



Ham Antenna Fits Almost Anywhere

[G3OJV] knows the pain of trying to operate a ham radio transmitter on a small lot. His recent video shows how to put up a workable basic HF antenna in a small backyard. The center of the system is a 49:1 unun. An unun is like a balun, but while a balun goes from balanced line to an unbalanced antenna, the unun has both sides unbalanced. You can see his explanation in the video below.

The tiny hand-size box costs well under $40 or $50 and covers the whole HF band at up to 200 W. The video shows the inside of the box which, as you’d expect, is a toroid with a few turns of wire.


The proposed antenna is an end-fed dipole fed with the unun. These are somewhat controversial with some people swearing they can’t work and others saying they are amazing. We are guessing they may not outperform a perfect antenna system, but we also know that you can have a lot of fun with almost any kind of radiator.

The element is about 33 ft long, but to make it fit, you can bend the antenna to fit your lot. Again, it is probably not optimal, but better than nothing. Erecting a wire antenna like this is easy and just requires some insulators and supporting rope or string. Using thin wire and low-profile rope, you can hide it nearly anywhere.

Does it work? Seems to in the video, at least judging by the SWR. As [G3OJV] says, why not try it before dismissing it?

We’ve seen other options, of course. We’ve also seen these end-fed antennas made with tiny band traps.


Arduino + Ham Radio = Texting

Over on the Spectrum web site, [Dale] — a relatively new ham radio operator — talks about his system for sending text messaging over VHF radios called HamMessenger. Of course, hams send messages all the time using a variety of protocols, but [Dale] wanted a self-contained and portable unit with a keyboard, screen, and a GPS receiver. So he built one. You can find his work on GitHub.

At the heart of the project is MicroAPRS, an Arduino firmware for packet radio. Instead of using a bigger computer, he decided to dedicate another Arduino to do everything but the modem function.

You can probably figure out the rest. A $10 GPS, a battery pack, a charge controller, and a few user interface parts like an OLED screen and a keyboard. In addition, there’s an SD card to store messages.

Of course, we couldn’t help but notice that our cell phone has a keyboard, screen, GPS, and storage. We might have been tempted to work out a way to connect the radio to it by Bluetooth. But we have to admit the little HamMessenger setup is cool-looking and probably lasts longer on a charge than our phone, too.

Heathkit IM-13 VTVM Repair

If you are under a certain age, you might not know the initialism VTVM. It stands for vacuum tube voltmeter. At first glance, you might just think that was shorthand for “old voltmeter” but, in fact, a VTVM filled a vital role in the old days of measuring instruments. [The Radio Mechanic] takes us inside a Heathkit IM-13 that needed some loving, and for its day it was an impressive little instrument.

Today, our meters almost always have a FET front end and probably uses a MOSFET. That means the voltage measurement probes don’t really connect to the meter at all. In a properly working MOSFET, the DC resistance between the gate and the rest of the circuit is practically infinite. It is more likely that a very large resistor (like 10 megaohms) is setting the input impedance because the gate by itself could pick up electrostatic voltage that might destroy the device. A high resistance like that is great when you make measurements because it is very unlikely to disturb the circuit you are trying to measure and it leads to more accurate measurements.


We take that for granted today, but a typical voltmeter in the old days was just a meter with some resistors in front of it. While a good meter would have relatively high resistance, it wasn’t as high as a FET. However, with a tube amplifier, a VTVM could also show a very high resistance and still make good measurements. The Heathkit meter used a dual tube as an amplifier along with some input resistor dividers to provide an 11 megaohm input. There was also a rectifier tube switched in to make AC measurements. In the end, the amplifier drove a conventional analog meter, but that load was isolated from the device under test so its relatively low resistance wasn’t important.

The repair seemed pretty simple, but it was fun to see the inside of one of these. Compare it to a digital meter today and it seems very strange, doesn’t it? If you want to read more about how VTVMs were used, there’s a copy of a 1951 Sylvania book about them online. Some people still prefer meters that move and, we admit, for certain tasks they beat even a digital bargraph.

The Low-Down On Long-Wave: Unlicensed Experimental Radio

In the 125 years since Marconi made his first radio transmissions, the spectrum has been divvied up into ranges and bands, most of which are reserved for governments and large telecom companies. Amidst all of the corporate greed, the “little guys” managed to carve out their own small corner of the spectrum, with the help of organizations like the American Radio Relay League (ARRL). Since 1914, the ARRL has represented the interests of us amateur radio enthusiasts and helped to protect the bands set aside for amateur use. To actually take advantage of the wonderful opportunity to transmit on these bands, you need a license, issued by the FCC. The licenses really aren’t hard to get, and you should get one, but what if you don’t feel like taking a test? Or if you’re just too impatient?

Well, fear not because there’s some space on the radio spectrum for you, too.

Welcome to the wonderful world of (legal!) unlicensed radio experimentation, where anything goes. Okay, not anything  but the possibilities are wide open. There are a few experimental radio bands, known as LowFER, MedFER, and HiFER where anyone is welcome to play around. And of the three, LowFER seems the most promising.

Gettin’ The Band Back Together

Before we dive into what the LowFER, MedFER, and HiFER bands actually are, it’s worth noting that these rules apply in the US only. That’s not to say that these bands are illegal elsewhere, but be sure to check your local frequency allocations before firing up a transmitter.

Ground wave radio propagation along the surface of the Earth. Courtesy of

LowFER, as the name would suggest, contains the lowest frequency range of the three, falling between 160 kHz and 190 kHz, with a whopping wavelength of around one mile. Also known as the 1750-meter band, this frequency range is well-suited for long transmission paths through ground wave propagation, a mode in which the radio signals move across the surface of the earth. This can easily carry even low-power signals hundreds of miles, and occasionally through some atmospheric black magic, signals have been known to travel thousands of miles. These ground wave signals also travel well across bodies of water, especially salt water.

MedFER is the medium frequency experimental band, specifically running from 510 kHz to 1,705 kHz. Now that range may sound similar, and it should because it’s also known as the AM Broadcast band! That’s right, you can listen in on this one with your old AM radio. There’s a catch though — amateur experimenters are limited to 0.1 W of transmit power, and can only use a three-meter long antenna. While that’s fine for playing around, there’s little chance of being heard very far away over the 500 W  professional stations with massive antennas that dominate the band.

And then there’s HiFER, the high-frequency experimental band. Much narrower than the others at only 14 kHz wide, it sits centered on 13.56 MHz. This band is commonly used for many RFID applications, including keycards, public transportation payments, and Nintendo Amiibo. Experimentation on this band is limited to extremely low power levels, and at such power levels signals only travel a few inches, which is perfect for RFID.

While there’s a lot that can be done on any of these bands, LowFER seems to be the one that yields itself to some serious fun. MidFER and HiFER both restrict power used so low that you’re not reaching outside of your house, or even arm’s length, respectively.

Low Frequencies, High Expectations

Like the other bands, LowFER does have some restrictions — but they’re much less limiting. First and foremost, the power into the last change of the transmitter can’t exceed 1 W. That’s still fairly low power, but there are some digital modes, such as WSPR, that are known to propagate around the world at 1 W on some frequencies. Antenna lengths are also limited to 15 meters– which seems awfully short compared to the nearly-two-kilometer wavelength. Generally, the length of such a wire antenna should be tuned to a fraction of a wavelength — 1, ½, ¼, etc. for maximum efficiency. In this case, “antenna length” also includes the transmission line between the radio and the antenna. For this reason, it’s common to connect antennas directly to LowFER radios to maximize the radiating length of the antenna.

As you may imagine, because the frequencies we’re dealing with here are so low, there are few commercially available solutions that let you get on-the-air with LowFER– but when has that ever stopped the hacker and amateur radio communities? Even with these limitations, we’ve seen some wonderful kHz-range projects, like this Altoids Tin Beacon and this Arduino-based transmitter. If you want to start out by listening in, there are a number of beacons on the air right now.

Bandwidth is obviously an issue down low, so LowFER applications probably want a microcontroller- or computer-based solution driving them, so there’s nothing to stop you from keeping the link running 24/7. The long antennas required also favor fixed operation. Intra-Hackerspace low-bitrate data networks?

How Low Can You Go?

So, now it’s your turn. What will you do with LowFER? Build a tiny transmitter and try to talk to a far-away friend? Send some waterfall art out into the æther, hoping some distant hacker sees it? Maybe even just engage in some good-old fashion CW. Although LowFER has been around for a while, we feel that there’s still a ton of untapped potential here for some crazy hacker fun. Just make sure to check (and obey!) your local laws, and tell us about anything awesome you do!