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149 Articles

A Super-Simple Standalone WSPR Beacon

June 14, 2024 by 26 Comments

We’ve said it before and we’ll say it again: being able to build your own radios is the best thing about being an amateur radio operator. Especially low-power transmitters; there’s just something about having the know-how to put something on the air that’ll reach across the planet on a power budget measured in milliwatts.

This standalone WSPR beacon is a perfect example. If you haven’t been following along, WSPR stands for “weak-signal propagation reporter,” and it’s a digital mode geared for exploring propagation that uses special DSP algorithms to decode signals that are far, far down into the weeds; signal-to-noise ratios of -28 dBm are possible with WSPR.

Because of the digital nature of WSPR encoding and the low-power nature of the mode, [IgrikXD] chose to build a standalone WSPR beacon around an ATMega328. The indispensable Si5351 programmable clock generator forms the RF oscillator, the output of which is amplified by a single JFET transistor. Because timing is everything in the WSPR protocol, the beacon also sports a GPS receiver, ensuring that signals are sent only and exactly on the even-numbered minutes. This is a nice touch and one that our similar but simpler WSPR beacon lacked.

This beacon had us beat on performance, too. [IgrikXD] managed to hit Texas and Colorado from the edge of the North Sea on several bands, which isn’t too shabby at all with a fraction of a watt.

Thanks to [STR-Alorman] for the tip.

[via r/amateurradio]

Passive Diplexer Makes One Antenna Act Like Two

May 22, 2024 by 24 Comments

Stay in the amateur radio hobby long enough and you might end up with quite a collection of antennas. With privileges that almost extend from DC to daylight, one antenna will rarely do everything, and pretty soon your roof starts to get hard to see through the forest of antennas. It may be hell on curb appeal, but what’s a ham to do?

One answer could be making one antenna do the work of two, as [Guido] did with this diplexer for dual APRS setups. Automatic Packet Reporting System is a packet radio system used by hams to transmit telemetry and other low-bandwidth digital data. It’s most closely associated with the 2-meter ham band, but [Guido] has both 2-meter (144.8-MHz) and 70-cm LoRa (433.775-MHz) APRS IGates, or Internet gateway receivers. His goal was to use a single broadband discone antenna for both APRS receivers, and this would require sorting the proper signals from the antenna to the proper receiver with a diplexer.

Note that [Guido] refers to his design as a “duplexer,” which is a device to isolate and protect a receiver from a transmitter when they share the same antenna — very similar to a diplexer but different. His diplexer is basically a pair of filters in parallel — a high-pass filter tuned to just below the 70-cm band, and a low-pass filter tuned just above the top of the 2-m band. The filters were designed using a handy online tool and simulated in LTSpice, and then constructed in classic “ugly” style. The diplexer is all-passive and uses air-core inductors, all hand-wound and tweaked by adjusting the spacing of the turns.

[Guido]’s diplexer performs quite well — only a fraction of a dB of insertion loss, but 45 to 50 dB attenuation of unwanted frequencies — pretty impressive for a box full of caps and coils. We love these quick and dirty tactical builds, and it’s always a treat to see RF wizardry in action.

Matchbox Transceiver Pushes The Spy Radio Concept To Its Limits

May 9, 2024 by 23 Comments

The Altoids tin has long been the enclosure of choice for those seeking to show off their miniaturization chops. This is especially true for amateur radio homebrewers — you really have to know what you’re doing to stuff a complete radio in a tiny tin. But when you can build an entire 80-meter transceiver in a matchbox, that’s a whole other level of DIY prowess.

It’s no surprise that this one comes to us from [Helge Fykse (LA6NCA)], who has used the aforementioned Altoids tin to build an impressive range of “spy radios” in both vacuum tube and solid-state versions. He wisely chose solid-state for the matchbox version of the transceiver, using just three transistors and a dual op-amp in a DIP-8 package. There’s also an RF mixer in an SMD package; [Helge] doesn’t specify the parts, but it looks like it might be from Mini-Circuits. Everything is mounted dead bug style on tiny pieces of copper-clad board that get soldered to a board just the right size to fit in a matchbox.

A 9 volt battery, riding in a separate matchbox, powers the rig. As do the earbud and tiny Morse key. That doesn’t detract from the build at all, and neither does the fact that the half-wave dipole antenna is disguised as a roll of fishing line. [Helge]’s demo of the radio is impressive too. The antenna is set up very low to the ground to take advantage of near vertical incidence skywave (NVIS) propagation, which tends to direct signals straight up into the ionosphere and scatter them almost directly back down. This allows for medium-range contacts like [Helge]’s 239 km contact in the video below.

Banging out Morse with no sidetone was a challenge, but it’s a small price to pay for such a cool build. We’re not sure how much smaller [Helge] can go, but we’re eager to see him try.

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Open HT Surgery Gives Cheap Transceiver All-Band Capabilities

March 22, 2024 by 34 Comments

Watch out, Baofeng; there’s a new kid on the cheap handy talkie market, and judging by this hardware and firmware upgrade to the Quansheng UV-K5, the radio’s hackability is going to keep amateur radio operators busy for quite a while.

Like the ubiquitous Baofeng line of cheap transceivers, the Quansheng UV-K5 is designed to be a dual-band portable for hams to use on the 2-meter VHF and 70-centimeter UHF bands. While certainly a useful capability, these bands are usually quite range-limited, and generally require fixed repeaters to cover a decent geographic area. For long-range comms you want to be on the high-frequency (HF) bands, and you want modulations other than the FM-only offered by most of the cheap HT radios.

Luckily, there’s a fix for both problems, as [Paul (OM0ET)] outlines in the video below. It’s a two-step process that starts with installing a hardware kit to replace the radio’s stock receiver chip with the much more capable Si4732. The kit includes the chip mounted on a small PCB, a new RF choke, and a bunch of nearly invisible capacitors. The mods are straightforward but would certainly benefit from the help of a microscope, and perhaps a little hot air rework. Once the hardware is installed and the new firmware flashed, you have an HT that can receive signals down to the 20-meter band, with AM and SSB modulations, and a completely redesigned display with all kinds of goodies.

It’s important to note that this is a receive-only modification — you won’t be transmitting on the HF bands with this thing. However, it appears that the firmware allows you to switch back and forth between HF receive and VHF/UHF transceive, so the radio’s stock functionality is still there if you need it. But at $30 for the radio and $12 for the kit, who cares? Having a portable HF receiver could be pretty handy in some situations. This looks like yet another fun hack for this radio; we’ve seen a few recently, including a firmware-only band expansion and even a Trojan that adds a waterfall display and a game of Pong. Continue reading “Open HT Surgery Gives Cheap Transceiver All-Band Capabilities” →

HF In Small Spaces

February 3, 2024 by 22 Comments

Generally, the biggest problem a new ham radio operator will come across when starting out on the high frequency (HF) bands is finding physical space for the antennas. For a quick example, a dipole antenna for the 20 m band will need around 10 m of wire, and the lower frequencies like 80 m need about four times as much linear space. But if you’re willing to trade a large space requirement for a high voltage hazard instead, a magnetic loop antenna might be just the ticket.

Loop antennas like these are typically used only for receiving, but in a pinch they can be used to transmit as well. To tune the antennas, which are much shorter than a standard vertical or dipole, a capacitor is soldered onto the ends, which electrically lengthens the antenna. [OM0ET] is using two loops of coax cable for the antenna, with each end soldered to one half of a dual variable capacitor which allows this antenna to tune from the 30 m bands to the 10 m bands, although he is using it mostly for WSPR on 20 m. His project also includes the use of an openWSPR module, meaning that he doesn’t have to dedicate an entire computer to run this mode.

The main downsides of antennas like these is that they are not omnidirectional, are not particularly good at transmitting, and develop a significantly high voltage across the capacitor as this similar mag loop antenna project demonstrated. But for those with extreme limitations on space or who, like [OM0ET] want a simple, small setup for running low-power applications like WSPR they can really excel. In fact, WSPR is a great mode for getting on the air at an absolute minimum of cost.

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A Ham Radio Answering Machine

December 8, 2023 by 15 Comments

For those who grew up with a cell phone in their hand, it might be difficult to imagine a time where the phone wasn’t fully integrated with voicemail. It sounds like a fantastical past, yet at one point a separate machine needed to be attached to the phone to record messages if no one was home to answer. Not only that, but a third device, a cassette tape, was generally needed as a storage device to hold the messages. In many ways we live in a much simpler world now, but in the amateur radio world one group is looking to bring this esoteric technology to the airwaves and [saveitforparts] is demonstrating one as part of a beta test.

The device is called the Boondock Echo, and while at its core it’s an ESP32 there’s a lot going on behind the scenes. It has an audio interface which is capable of connecting to a radio given the correct patch cable; in this case with a simple Baofeng handheld unit. The answering machine can record any sounds that come in. However, with a network connection the recordings are analyzed with an AI which can transcribe what it hears and even listen for specific call signs, then take actions such as sending emails when it hears triggers like that. Boondock also plans for this device to be capable of responding as well, but [saveitforparts] was not able to get this working during this beta test.

While an answering machine might seem like a step backwards technologically, an answering machine like this, especially when paired with Google Voice-like capabilities from an AI, has a lot of promise for ham radio operators. Even during this test, [saveitforparts] lost a radio and a kind stranger keyed it up when it was found, which was recorded by the Boondock Echo and used to eventually recover the radio. Certainly there are plenty of other applications as well, such as using AI instead of something like an Arduino to do Morse decoding.

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A Canned Ham Ham Antenna

November 16, 2023 by 29 Comments

If you’d have asked us for odds on whether you could successfully turn a canned ham into an amateur radio antenna, we’d have declined the offer. Now, having seen [Ben Eadie (VE6SFX)]’s “hamtenna” project, we’d look at just about any “Will it antenna?” project with a lot less skepticism than before.

To be painfully and somewhat unnecessarily clear about [Ben]’s antenna, the meat-like product itself is not in the BOM for this build, although he did use it as sustenance. Rather, it was the emptied and cleaned metal can that was the chief component of the build, along with a few 3D printed standoffs and the usual feedline and connectors. This is a slot antenna, a design [Ben] recently experimented with by applying copper foil tape to his car’s sunroof. This time around, the slot was formed by separating the top and bottom of the can using the standoffs and electrically connecting them with a strip of copper tape.

Connected to a stub of coax and a BNC connector, a quick scan with a NanoVNA showed a fantastic 1.26:1 SWR in the center of the 70-cm ham band, and a nearly flat response all the way across the band. Results may vary depending on the size of canned ham you sacrifice for this project; [Ben]’s can measured just about 35 cm around, a happy half-wavelength coincidence. And it actually worked in field tests — he was able to hit a local repeater and got good signal reports. All that and a sandwich? Not too shabby.

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