ham radio

224 Articles

Ham Radio Traffic Logger Using A Bug In Baofeng Electronics

June 10, 2021 by 22 Comments

A Baofeng radio is often one of the first purchases a new ham radio operator makes these days due to the decent features and low price tag. They are far from perfect, but with a bit of creative inspiration, it’s possible to make the quirks work in your favor. By taking advantage of a loud pop on the earphone outputs whenever the LCD backlight turns on, [WhiskeyTangoHotel] built a radio traffic counter using an ESP8266.

Whenever there is a transmission on one of the frequencies the radio is tuned to, the backlight turns on. Connecting the audio output to an oscilloscope, [WhiskeyTangoHotel] measured a 5V spike whenever this happens. Using a pair of diodes in series to drop the voltage to a safe level, the ESP8266 detects the voltage spike and updates a Google spreadsheet with the timestamp via IFTTT.

This gave [WhiskeyTangoHotel] empirical data on how much traffic passes through the local VHF repeater, but we wouldn’t blame them if the hack itself was the real motivator.

Of course, this would also be a perfect application for the RTL-SDR, which should allow you to do the above and much more, all in software. Add a bit of AI and you can even extract the call signs. The RTL-SDR is also a good tool for learning about RF modulation.

UV5-R image via PE1RQM

QMESH: LoRa Mesh Networked Voice Communications

June 6, 2021 by 32 Comments

LoRa is great for sending short data packets over long ranges but is not normally suitable for voice communications. [Dan Fay] is looking to change this with QMesh, a synchronized, flooded mesh network protocol for ham radio applications.

In a flooded mesh network every node repeats every message it receives. This has the theoretical advantage of making the network self-healing if a single node stops working, but often just means that the nodes will interfere with each other. Thanks to some characteristics of LoRa, [Dan] is using several tricks to get around this packet collision problem. LoRa network can make use of the “capture effect”, which allows a receiver to differentiate between two packets if the power level difference is large enough. This is further improved by adding forward error correction and slightly changing the frequency and timing of the LoRa chirps. QMesh also implements TDMA (Time Division Multiple Access) by splitting transmission into time slots, and only transmitting every third slot. This means it is operating on a 33% duty cycle, which is much higher than the 0.1%-10% allowed on license-free ISM-bands, which legally limits it to the ham bands.

On the hardware side, [Dan] has been using the STM32 NUCLEO-144 development boards with F4/L4/F7/H7 microcontrollers and a custom shield with a 1 W LoRa module and OLED screen. While [Dan] wants to eventually build handheld radios, he plans to first develop small FM repeaters that encode voice as codec2 and use QMesh as a backhaul. QMesh is still under development, but we would love to see the results of some long-range testing, and we are excited to see how it matures.

If your interested in a more basic LoRa-based human-to-human messaging system, take a look at Meshtastic. It’s been going very rapidly over the past year. To learn more about LoRa and other digital modulation schemes, check out the crash course we did with an SDR a while back.

3D Printer Makes Ham Antenna Portable

February 9, 2021 by 8 Comments

You don’t normally think of a 3D printer as a necessity for an antenna project. However, if you are interested in making a handy portable antenna, you might want to melt some plastic. [N2MXX] has an end fed antenna winder design that also contains the necessary matching toroid. This would be just the thing to throw in your backpack for portable operation.

The end-fed configuration is handy for portability too, because you can easily secure one end and feed the other end. Compare that to a dipole where you have to feed a high point and secure both ends.

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A Few Of My Favorite Things: Amateur Radio

January 21, 2021 by 50 Comments

Hackaday has among its staff a significant number of writers who also hold amateur radio licenses. We’re hardware folks at heart, so we like our radios homebrew, and we’re never happier than when we’re working at high frequencies.

Amateur radio is a multi-faceted hobby, there’s just so much that’s incredibly interesting about it. It’s a shame then that as a community we sometimes get bogged down with negativity when debating the minutia. So today let’s talk about a few of my favourite things about the hobby of amateur radio. I hope that you’ll find them interesting and entertaining, and in turn share your own favorite things in the comments below.

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A One-Transistor Ham Transmitter Anyone Can Build

January 20, 2021 by 65 Comments

What attracts a lot of people to amateur radio is that it gives you the ability to make your own gear. Scratch-building hams usually start by making their own antennas, but eventually, the itch to build one’s own radio must be scratched. And building this one-transistor transmitter is just about the simplest way to dive into the world of DIY radio.

Of course, limiting yourself to eight components in total entails making some sacrifices, and [Kostas (SV3ORA)]’s transmitter is clearly a study in compromise. For starters, it’s only a transmitter, so you’ll need to make other arrangements to have a meaningful conversation. You’ll also have to learn Morse code because the minimalist build only supports continuous-wave (CW) mode, although it can be modified for amplitude modulation (AM) voice work.

The circuit is flexible enough that almost any part can be substituted and the transmitter will still work. Most of the parts are junk-bin items, although the main transformer is something you’ll have to wind by hand. As described, the transformer not only provides feedback to the transistor oscillator, but also has a winding that powers an incandescent pilot lamp, and provides taps for attaching antennas of different impedances — no external tuner needed. [SV3ORA] provides detailed transformer-winding instructions and shows the final build, which looks very professional and tidy. The video below shows the rig in action with a separate receiver providing sidetone; there’s also the option of using one of the WebSDR receivers sprinkled around the globe to verify you’re getting out.

This little transmitter looks like a ton of fun to build, and we may just try it for our $50 Ham series if we can find all the parts. Honestly, the hardest to come by might be the variable capacitor, but there are ways around that too.

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Manual Antenna Tuner Shows How Homebrewing Is Done

January 15, 2021 by 10 Comments

If there’s anything about amateur radio that has more witchcraft in it than the design and implementation of antennas, we don’t know what it would be. On the face of it, hanging out a chunk of wire doesn’t seem like it should be complicated, but when you dive into the details, building effective antennas and matching them to the job at hand can be pretty complex.

That doesn’t mean antenna topics have to remain a total mystery, of course, especially once someone takes the time to explain things properly. [Charlie Morris (ZL2CTM)] recently did this with a simple antenna tuner, a device used to match impedances between a transmitter and an antenna. As he explains in the first video below, his tuner design is really just a Wheatstone bridge where the antenna forms half of one leg. A toroidal transformer with multiple taps and a variable capacitor forms an LC circuit that matches the high impedance antenna, in this case a multi-band end-fed halfwave, with the nominal 50-ohm load expected by the transceiver. A small meter and a diode detector indicate when the bridge is balanced, which means the transceiver is seeing the proper load.

The second video below shows the final implementation of the tuner; as a fan of QRP, or low-power operation, [Charlie] favors simple, lightweight homebrew gear that can be easily taken into the field, and this certainly fits the bill. A final video shows the tuner in use in the field, with a NanoVNA proving what it can do. As usual, [Charlie] protests that he not an expert and that he’s just documenting what he did, but he always does such a good job of presenting the calculations involved in component selection that any ham should be able to replicate his builds.

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Bringing Modern Control To An Old Radio

January 11, 2021 by 13 Comments

The modern ham radio shack can take many forms. Some are shrines the “boat anchor” radios of old, named for their considerable weight. Others are simply a small, unassuming software-defined radio (SDR) hooked up to a laptop. Nowadays, many shacks fall somewhere in the middle. It’s not uncommon to find a sleek Icom IC-7300 sitting atop an ancient Hallicrafters SX-115 (which sounds suspiciously like the author’s setup). When a ham wants to work a digital mode such as FT-8, they will undoubtedly reach for a newer radio complete with USB (Universal Serial Bus in this case, not Upper Sideband) rig control — but what if the newest piece of equipment they have is a thirty-year-old Kenwood?

If that sounds like you, then fear not because [Steve Bossert] has you covered. He took his trusty Kenwood TS-50, a classic radio from 1993 whose most advanced feature is fuzzy logic, and upgraded it with USB (again, the serial bus) control.

When Kenwood designed the TS-50, they had computer control in mind. There’s a hidden port on the bottom of the unit which reveals a connector that mates with Kenwood’s proprietary (and expensive) set of serial control cables. Thankfully, the engineers over at Kenwood decided to use UART for PC communication, so slapping a USB port in the radio’s case isn’t as daunting as it may sound. [Steve] picked up a CP2104 USB-TTL UART Serial Adapter and wired it up to the radio’s control port. After a bit of drilling, screwing, and gluing, the radio had an upgraded (and non-proprietary!) interface compatible with the ever-popular hamlib. While this doesn’t cover all radio control functions, it gets you tuning, which is pretty important. For a fully modern radio experience, [Steve] suggests using the 8-pin mic connector along with an interface such as Rigblaster or Signalink. This adds PTT and audio signal routing.

If you want to try this for yourself, be sure to check out [Steve]’s extremely well-documented writeup. You could even take this a step further and control your TS-50 from your smartphone with this HTML5 interface we saw a few months back.