Radio Hacks

1317 Articles

Better Antennas Via Annealing (Simulated)

June 18, 2023 by 26 Comments

If you want to simulate a tic-tac-toe game, that’s easy. You can evaluate every possible move in a reasonable amount of time. Simulating antennas, however, is much harder. [Rosrislav] has been experimenting with using simulated annealing to iterate antenna designs, and he shares his progress in a recent blog post.

For many problems, it simply isn’t possible to try all possible inputs to determine what provides the “best” result. Instead of trying every single input or set of inputs, you can try random ones and discard all but the best guesses. Then you make small changes and try again. The only problem is that the algorithm may lock in on a “local maximum” — that is, a relatively high value that isn’t the highest because it forms a peak that isn’t the highest peak. Or, if you are looking for a minimum, you may lock on to a local minimum — same thing.

To combat that, simulated annealing works like annealing a metal. The simulation employs a temperature that cools over time. The higher the temperature, the more likely large changes to the input are to occur.

The Python program uses the PyNEC package to provide simulation. The program sets up random antenna lengths and finds the projected gain, attempting to optimize for maximum gain.

The post is long on code and short on details, so you will probably want to read the Python source to see exactly what it is doing. But it could probably serve as a template to do other simulated annealing simulations for other antennas or anything you had a simulation engine to evaluate.

Several techniques allow you to optimize things that are too hard to search exhaustively, and we’ve talked about simulated annealing and genetic algorithms before. However, lately, we’ve been more interested in annealing 3D prints.

Detecting Meteors With SDR

June 18, 2023 by 10 Comments

The simplest way to look for meteors is to go outside at night and look up — but it’s not terribly effective. Fortunately, there’s a better way: radio. With a software-defined radio and a little know-how from [Tech Minds], you can easily find them, as you can see in the video below.

This uses the UK meteor beacon we’ve looked at before. The beacon pushes an RF signal out so you can read the reflections from meteors. If you are too far from the beacon, you may need a special antenna or you might have to find another beacon altogether. We know of the Graves radar in France and we have to wonder if you couldn’t use some commercial transmitter with a little experimentation.

[Tech Minds] has some practical tips to share if you want to try doing it yourself. If you want to see what a detected meteor looks like, you can visit the UK beacon’s gallery page.

We saw another presentation on the UK beacon earlier this year. Using commercial transmitters sounds like it might be easy, but apparently, it isn’t.

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Ham Pairs Nicely With GMRS

June 17, 2023 by 37 Comments

Ignoring all of the regulations, band allocations, and “best amateur practices,” there’s no real fundamental difference between the frequencies allocated to the Family Radio Service (FRS), the General Mobile Radio Service (GMRS), the Multi-Use Radio Service (MURS), and the two-meter and 70-centimeter bands allocated to licensed ham radio operators. The radio waves propagate over relatively short distances, don’t typically experience any skip, and are used for similar activities. The only major difference between these (at least in the Americas or ITU region 2) is the licenses you must hold to operate on the specific bands. This means that even though radios are prohibited by rule from operating across these bands, it’s often not too difficult to find radios that will do it anyway.

[Greg], aka [K4HSM], was experimenting with a TIDRADIO H8 meant for GMRS, which in North America is a service used for short-range two-way communication. No exams are required, but a license is still needed. GMRS also allows for the use of repeaters, making it more effective than the unlicensed FRS. GMRS radios, this one included, often can receive or scan frequencies they can’t transmit on, but in this case, the limits on transmitting are fairly easy to circumvent. While it isn’t allowed when programming the radio over Bluetooth, [K4HSM] found that programming it from the keypad directly will allow transmitting on the ham bands and uses it to contact his local two-meter and 70-cm repeaters as a proof-of-concept.

The surprising thing about this isn’t so much that the radio is physically capable of operating this way. What’s surprising is that this takes basically no physical modifications at all, and as far as we can tell, that violates at least one FCC rule. Whether or not that rule makes any sense is up for debate, and it’s not likely the FCC will break down your door for doing this since they have bigger fish to fry, but we’d definitely caution that it’s not technically legal to operate this way.

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Long-Distance Wi-Fi With Steam Deck Server

June 16, 2023 by 11 Comments

It’s no secret that the Steam Deck is a powerful computer, especially for its price point. It has to be capable enough to run modern PC games while being comfortable as a handheld, all while having a useful amount of battery life. Thankfully Valve didn’t lock down the device like most smartphone manufacturers, allowing the computer to run whatever operating system and software the true owner of the device wants to run. That means that a whole world of options is open for this novel computer, like using it to set up an 802.11ah Wi-Fi network over some pretty impressive distances.

Of course the Steam Deck is more of a means to an end for this project; the real star of the show is DragonOS, a Debian-based Linux distribution put together by [Aaron] to enable easy access to the tools needed for plenty of software-defined radio projects like this one. Here, he’s using it to set up a long-distance Wi-Fi network on one side of a lake, then testing it by motoring over to the other side of the lake to access the data from the KrakenSDR setup running on the Deck, as well as performing real-time capture of IQ data that was being automatically demodulated and feed internally to whispercpp.

While no one will be streaming 4K video over 802.11ah, it’s more than capable of supporting small amounts of data over relatively large distances, and [Aaron] was easily able to SSH to his access point from over a kilometer away with it. If the lake scenery in the project seems familiar at all, it’s because this project is an extension of another one of his DragonOS projects using a slightly lower frequency to do some impressive direction-finding, also using the Steam Deck as a base of operations.

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Ham Almost Cooks ‘Dog

June 14, 2023 by 34 Comments

For those of us licensed in other countries it comes as something of a surprise to find that American radio amateurs now have to run RF exposure calculations as part of their licence requirements. [Ham Radio Crash Course] as approached this in a unique fashion, by running around 800 watts of 6-metre power into a vertical antenna festooned with hotdogs. That’s right, this ham is trying to cook some ‘dawgs! Is his station producing dangerous levels of power that might cook passers-by?

Of course, aside from a barely-warmed line along where the ‘dogs were attached to the antenna there’s no heating to be found. But we think he’s trying to make the point in the video below the break about the relative pointlessness of applying RF field limits which are definitely relevant at much higher frequencies, to hams at low frequencies.

It leaves us curious as to how that 800 watts could be efficiently transferred into the sausages and really cook them. Strapping them to a vertical is we think the equivalent of strapping anything resistive to a conductor, they do not form a significant  enough part of the circuit. We think that even six metres could cook a sausage if it could be efficiently coupled into it, so we’d suggest putting a grounded sausage up the middle of a close-wound helix.

If you have any thoughts on the RF exposure calculations, or on the best way to cook a ‘dog with 6m, we’d love to hear the, in the comments. Meanwhile, this isn’t the first piece of ‘dog-based shenanigans we’ve brought you.

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Passionate Hams Make Their Mark On The Hack Chat

June 12, 2023 by 63 Comments

Let’s be honest — there are some not very pleasant stereotypes associated with amateur radio, at least if you ask outsiders. Hams are often thought of as being in two camps: old guys who can’t figure out modern technology or conspiracy theorists who think their knowledge of radio will give them an edge after the world becomes a post-apocalyptic hellscape. We’ll leave it to you to decide which is the worse brush to be painted with.

As is often the case, the best way to fight such ignorance is with education and outreach. Events like our weekly Hack Chat are a perfect platform for that, as it allows the curious to ask questions and get answers directly from subject matter experts. This is precisely why we invited Mark Hughes and Beau Ambur to helm last week’s Chat. The fact that they’re both relatively recent licensees makes them uniquely qualified to shed some light on what it’s like to become part of the ham radio community in the 21st century. As an added bonus, they’re both sharp and articulate technologists — about as far as you can get from the mental image of the doddering old granddad who prefers the simplicity of the Morse key to those newfangled smarty-phones.

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Listening To The ISS On The Cheap

June 10, 2023 by 36 Comments

Like any hobby, amateur radio has no upper bounds on what you can spend getting geared up. Shacks worth tens of thousands of dollars are easy to come by, and we’ll venture a guess that there are hams out there pushing six figures with their investment in equipment. But hands down, the most expensive amateur radio station ever has to be the one aboard the  International Space Station.

So what do you need to talk to a $100 billion space station? As it turns out, about $60 worth of stuff will do, as [saveitforparts] shows us in the video below. The cross-band repeater on the ISS transmits in the 70-cm ham band, meaning all that’s needed to listen in on the proceedings is a simple “handy talkie” transceiver like the $25-ish Baofeng shown. Tuning it to the 437.800-MHz downlink frequency with even a simple whip antenna should get you some reception when the ISS passes over.

In our experience, the stock Baofeng antenna isn’t up to the job, so something better like the Nagoya shown in the video is needed. Better still is a three-element Yagi tuned down slightly with the help of a NanoVNA; coupled with data on when the ISS will be within line-of-sight, picking up the near-constant stream of retransmissions from the station as Earth-based hams work it should be a snap — even though [saveitforparts] only listened to the downlink frequency here, for just a bit more of an investment it’s also possible for licensed hams to uplink to the ISS on 145.900 MHz.

For those who want a slightly higher level of difficulty, [saveitforparts] also has some tips on automating tracking with an old motorized mount for CCTV cameras. Pitchfork notwithstanding, it’s not the best antenna tracker, but it has promise, and we’re eager to see how it pans out — sorry. But in general, the barrier to entry for getting into space communications is so low that you could easily make this a weekend project. We’ve been discussing this and other projects on the new #ham-shack channel over on the Hackaday Discord. You should pop over there and check it out — we’d be happy to see you there.

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