amateur

32 Articles

Spy Transceiver Makes Two Tubes Do The Work Of Five

May 19, 2023 by 26 Comments

Here at Hackaday, we love following along with projects as they progress. That’s especially true when a project makes a considerable leap in terms of functionality from one version to another, or when the original design gets more elegant. And when you get both improved function and decreased complexity at the same time? That’s the good stuff.

Take the recent improvements to a vacuum tube “spy radio” as an example. Previously, [Helge (LA6NCA)] built both a two-tube transmitter and a three-tube receiver, either of which would fit in the palm of your hand. A little higher math seems to indicate that combining these two circuits into a transceiver would require five tubes, but that’s not how hams like [Helge] roll. His 80-m CW-only transceiver design uses only two tubes and a lot of tricks, which we admit we’re still wrapping our heads around. On the receive side, one tube serves as a mixer/oscillator, combining the received signal with a slightly offset crystal-controlled signal to provide the needed beat frequency. The second tube serves as the amplifier, both for the RF signal when transmitting, and for audio when receiving.

The really clever part of this build is that [Helge] somehow stuffed four separate relays into the tiny Altoids tin chassis. Three of them are used to switch between receive and transmit, while the fourth is set up as a simple electromagnetic buzzer. This provides the sidetone needed to effectively transmit Morse code, and is about the simplest way we’ve ever seen to address that need. Also impressive is how [Helge] went from a relatively expansive breadboard prototype to a much more compact final design, and how the solder was barely cooled before he managed to make a contact over 200 km. The video below has all the details.

Continue reading “Spy Transceiver Makes Two Tubes Do The Work Of Five” →

Two-Tube Spy Transmitter Fits In The Palm Of Your Hand

March 29, 2023 by 13 Comments

It’s been a long time since vacuum tubes were cutting-edge technology, but that doesn’t mean they don’t show up around here once in a while. And when they do, we like to feature them, because there’s still something charming, nay, romantic about a circuit built around hot glass and metal. To wit, we present this compact two-tube “spy radio” transmitter.

From the look around his shack — which we love, by the way — [Helge Fykse (LA6NCA)] really has a thing for old technology. The typewriter, the rotary phones, the boat-anchor receiver — they all contribute to the retro feel of the space, as well as the circuit he’s working on. The transmitter’s design is about as simple as can be: one tube serves as a crystal-controlled oscillator, while the other tube acts as a power amplifier to boost the output. The tiny transmitter is built into a small metal box, which is stuffed with the resistors, capacitors, and homebrew inductors needed to complete the circuit. Almost every component used has a vintage look; we especially love those color-coded mica caps. Aside from PCB backplane, the only real nod to modernity in the build is the use of 3D printed forms for the coils.

But does it work? Of course it does! The video below shows [Helge] making a contact on the 80-meter band over a distance of 200 or so kilometers with just over a watt of power. The whole project is an excellent demonstration of just how simple radio communications can be, as well as how continuous wave (CW) modulation really optimizes QRP setups like this.

Continue reading “Two-Tube Spy Transmitter Fits In The Palm Of Your Hand” →

Enormous Metal Sculpture Becomes An Antenna

March 23, 2023 by 16 Comments

Those who have worked with high voltage know well enough that anything can be a conductor at high enough voltages. Similarly, amateur radio operators will jump at any chance to turn a random object into an antenna. Flag poles, gutters, and even streams of water can be turned into radiating elements for a transmitter, but the members of this amateur radio club were thinking a little bit bigger when they hooked up their transmitter to this giant sculpture.

For those who haven’t been to the Rochester Institute of Technology (RIT) in upstate New York, the enormous metal behemoth is not a subtle piece of artwork and sits right at the entrance to the university. It’s over 70 feet tall and made out of bronze and steel, a dream for any amateur radio operator. With the university’s permission and some help to ensure everyone’s safety during the operation, the group attached a feedline to the sculpture with a magnet, while the shield wire was attached to a ground rod nearby. A Yaesu FT-991 running on only 5 watts and transmitting in the 20-meter band was able to make contacts throughout much of the eastern United States with this setup.

This project actually started as an in-joke within the radio club, as reported by Reddit user [bbbbbthatsfivebees] who is a member. Eventually the joke became reality, as the sculpture is almost a perfect antenna for certain ham bands. Others in the comments noted that they might have better luck with lower frequency bands such as the 40-meter band or possibly the 60-meter band, due to the height of the structure. And, for those who are still wondering if you really can use a stream of water to transmit radio waves, it is indeed possible.

Hunting For Space Pirates

February 24, 2023 by 14 Comments

Ever since the first artificial satellite was launched into orbit, radio operators around the world have been tuning in to their space-based transmissions. Sputnik 1 only sent back pulses of radio waves, but in the decades to follow ever more advanced radio satellites were put into service that could support two-way communications from Earth to space and back again.

Some of these early satellites were somewhat lacking in security, though, and have been re-purposed by various pirates around the world for their own ends. [Gabe] aka [saveitforparts] is here to show us how to hunt for those pirates and listen in on their radio traffic.

Pirates on these satellites have typically used them for illicit activities, and it is still illegal to use them for non-governmental or non-military purposes, so [Gabe] notes that he will only be receiving, not transmitting. The signals he is tuning in to are VHF transmissions, specifically around 220 MHz. That puts them easily within the reach of the RTL-SDR and common ham radio equipment, but since they are coming from space a more directional antenna is needed. [Gabe] quickly builds a Yagi antenna from scrap, tuned specifically to 255 MHz, and mounts it to an old remote-controlled security camera mount which allows him to point it exactly at the satellite and monitor transmissions.

From there he is able to pick up what looks like a few encrypted and/or digital transmissions, plus analog transmissions of likely pirates speaking a language he guesses to be Portuguese. He also hears what he thinks is a foreign TV broadcast, but oddly enough turns out to be NPR. These aren’t the only signals in space to tune to, either. There are plenty of purpose-built ham radio satellites available for any licensed person to use, and we’ve also seen this other RTL-SDR configured to snoop on Starlink signals.

Continue reading “Hunting For Space Pirates” →

A Linux Distro For All Your Ham Needs

February 23, 2023 by 29 Comments

For anyone new to the world of ham radio, one of the things that takes a little getting used to is visiting the websites of authoritative experts in various fields and feeling like you’ve traveled back to the Internet of 1999. As a hobby that lends itself to extremely utilitarian amateurs, the software side can feel a little left behind like that. [Andy] aka [KB1OIQ], on the other hand, is also a Linux enthusiast and has been putting together a complete Linux distribution with everything needed to operate a radio in the modern era.

While most ham radio software seems to be developed for Windows, there is a lot available for Linux. It just takes a bit of tinkering and experimentation to get everything configured just right. Andy’s Ham Radio Linux, or AHRL, takes a lot of the guesswork out of this. The distribution includes everything from contact logging software to antenna modeling, propagation forecasting, and electronic design. While tools like this are largely optional for operating radios themselves, there are also tools included to allow the user to operate various digital modes as well, which require some sort of computer interface to use.

The other design consideration [Andy] made was something that most hams consider when choosing software, which is that it should be able to run on extremely modest hardware. To that end, the distribution is based around Xubuntu and can run on ten-year-old machines with as little as 2 GB of RAM. And, for those interested more in software-defined radio specifically, there is another Debian-based Linux distribution called DragonOS that we’ve featured a few other times as well which is also worth checking out.

Continue reading “A Linux Distro For All Your Ham Needs” →

Translating And Broadcasting Spoken Morse Code

January 24, 2023 by 24 Comments

When the first radios and telegraph lines were put into service, essentially the only way to communicate was to use Morse code. The first transmitters had extremely inefficient designs by today’s standards, so this was more a practical limitation than a choice. As the technology evolved there became less and less reason to use Morse to communicate, but plenty of amateur radio operators still use this mode including [Kevin] aka [KB9RLW] who has built a circuit which can translate spoken Morse code into a broadcasted Morse radio signal.

The circuit works by feeding the signal from a microphone into an Arduino. The Arduino listens for a certain threshold and keys the radio when it detects a word being spoken. Radio operators use the words “dit” and “dah” for dots and dashes respectively, and the Arduino isn’t really translating the words so much as it is sending a signal for the duration of however long each word takes to say. The software for the Arduino is provided on the project’s GitHub page as well, and uses a number of approaches to make sure the keyed signal is as clean as possible.

[Kevin] mentions that this device could be used by anyone who wishes to operate a radio in this mode who might have difficulty using a traditional Morse key and who doesn’t want to retrain their brain to use other available equipment like a puff straw or a foot key. The circuit is remarkably straightforward for what it does, and in the video below it seems [Kevin] is having a blast using it. If you’re still looking to learn to “speak” Morse code, though, take a look at this guide which goes into detail about it.

Thanks to [Dragan] for the tip!

Continue reading “Translating And Broadcasting Spoken Morse Code” →

Add Mycelium To Your Mesh Networks

October 26, 2021 by 21 Comments

In many parts of the world, days after a good rainfall, it’s fairly common to see various species of mushrooms popping up out of the ground. These mysterious organisms aren’t the whole story, though. The living being is a vast network of hidden fibers, called mycelium, spreading through the ground and into any other organic material it can colonize. Its air of mystery and its vast reach are the inspiration for entire Star Trek shows and, of course, projects like this LoRa-based mesh network called Mycelium.

Mycelium is the invention of [Catamine] and includes many novel features compared to more typical mesh networks. For one, it is intended to be used in low power applications to give users the ability to send messages over a distributed network rather than a centralized network like a cell phone service provider. For another, the messages are able to be encrypted and authenticated, which is not currently possible with other mesh networks such as APRS. The idea is that a large network of people with nothing more complicated than an ESP32, an antenna, and this software would be able to communicate securely in situations where a centralized network is not available, whether that is from something like a natural disaster or from a governmental organization disabling the Internet during a political upheval.

The mesh network is currently in active development, and while messages can not yet be sent, the network is able to recognize nodes and maintain a keybase. There are certainly plenty of instances where something like this would be useful as we’ve seen before from other (non-encrypted) LoRa-based network solutions which are built around similar principles.

Thanks to [dearuserhron] for the tip!