A Geek’s Revenge For Loud Neighbors

It seems [Kevin] has particularly bad luck with neighbors. His first apartment had upstairs neighbors who were apparently a dance troupe specializing in tap. His second apartment was a town house, which had a TV mounted on the opposite wall blaring American Idol with someone singing along very loudly. The people next to [Kevin]’s third apartment liked music, usually with a lot of bass, and frequently at seven in the morning. This happened every day until [Kevin] found a solution (Patreon, but only people who have adblock disabled may complain).

In a hangover-induced rage that began with thumping bass at 7AM on a Sunday, [Kevin] tore through his box of electronic scrap for every capacitor and inductor in his collection. An EMP was the only way to find any amount of peace in his life, and the electronics in his own apartment would be sacrificed for the greater good. In his fury, [Kevin] saw a Yaesu handheld radio sitting on his desk. Maybe, just maybe, if he pressed the transmit button on the right frequency, the speakers would click. The results turned out even better than expected.

With a car mount antenna pointed directly at the neighbor’s stereo, [Kevin] could transmit on a specific, obscure frequency and silence the speakers. How? At seven in the morning on a Sunday, you don’t ask questions. That’s a matter for when you tell everyone on the Internet.

Needless to say, using a radio to kill your neighbor’s electronics is illegal, and it might be a good idea for [Kevin] to take any references to this escapade off of the Internet. It would be an even better idea to not put his call sign online in the future.

That said, this is a wonderful tale of revenge. It’s not an uncommon occurrence, either. Wikihow, Yahoo Answers and Quora – the web pages ‘normies’ use for the questions troubling their soul – are sometimes unbelievably literate when it comes to unintentional electromagnetic interference, and some of the answers correctly point out grounding a stereo and putting a few ferrite beads on the speaker cables is the way to go. Getting this answer relies entirely on asking the right question, something I suspect 90% of the population is completely incapable of doing.

While [Kevin]’s tale is a grin-inducing two-minute read, You shouldn’t, under any circumstances, do anything like this. Polluting the airwaves is much worse than polluting your neighbor’s eardrums; one of them violates municipal noise codes and another is breaking federal law. It’s a good story, but don’t do it yourself.

Editor’s Note: Soon after publishing our article [Kevin] took down his post and sent us an email. He realized that what he had done wasn’t a good idea. People make mistakes and sometimes do things without thinking. But talking about why this was a bad idea is one way to help educate more people about responsible behavior. Knowing you shouldn’t do something even though you know how is one paving stone on the path to wisdom.
–Mike Szczys

The Michigan Mighty-Mite Rides Again

One of the best things about having your amateur radio license is that it allows you to legally build and operate transmitters. If you want to build a full-featured single-sideband rig with digital modes, have at it. But there’s a lot of fun to be had and a lot to learn from minimalist builds like this Michigan Mighty-Mite one-transistor 80-meter band transmitter.

If the MMM moniker sounds familiar, it may be because of this recent post. And in fact, [W2AEW]’s build was inspired by the same SolderSmoke blog posts that started [Paul Hodges] on the road to his breadboard and beer can build.  [W2AEW]’s build is a bit sleeker, to be sure, but where the video really shines is in the exploration and improvement of the signal quality. The basic Mighty-Mite outputs a pretty dirty signal – [W2AEW]’s scope revealed 5 major harmonic spikes, and what was supposed to be a nice sine wave was full of divots and potholes. There’s only so much one transistor, a colorburst crystal and a couple of capacitors can do, so the video treats us to an explanation of the design of the low-pass filter needed to get rid of the harmonics and clean up the output into a nice solid sine wave.

If your Morse skills aren’t where they should be to take advantage of the Might-Mite’s CW-only mode, then you’ll need to look at other modulations. Maybe a tiny FM transmitter would suit your needs better?

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Whiskey Tango Foxtrot is the Phonetic Alphabet?

Sometimes words just have to be spelled for others. I’ve been on phone conversations where the person on the other end is spelling for me and it’s painful. “Was that a ‘b’ or a ‘p’?” Sometimes they’ll try on the fly to use words with the beginning letter trying to convey the letter: “B as in boy”. Then they’ll get stumped mumbling while they think desperately for ‘k’ words… ‘ketchup’. Okay, but is that really ketchup or catsup? Now think how much easier spelling is on a phone than over a poor quality radio channel. What we say, and how we say it is the key to our brain’s ability to error correct human speech. It’s a solved problem that was built into radio etiquette long ago.

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Ten Mile Raspberry Pi WiFi (with a Catch)

How would you like to have a WiFi connection that covers 10 miles? Or how about an even wider network made up of a mesh of multiple nodes? It is possible, but there is a catch: you probably need a ham radio license to do it (at least, you do in the United States).

What makes it possible is the realization that conventional WiFi channels 1-6 are inside an existing US ham band. That means (if you are a ham) you can elect to use FCC part 97 rules instead of part 15 that governs WiFi routers. That means you can use more power and–even more importantly–better antennas to get greater range.

Traditionally, hams have used custom firmware for Netgear routers or Ubiquiti hardware. However, [WZ0W] recently posted his experience using Raspberry Pi boards as mesh nodes. The code (which also works with some other single board computers) is available on GitHub (with details on the project blog). [WZ0W] points out that, unlike using a consumer router, using a Pi provides a reasonably powerful computer for hosting services as well as hosting the network.

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You Can Learn a Lot from a Dummy (Load)

If you work on RF circuits–even if you aren’t a ham radio operator–you ought to have a dummy load. A dummy load is a non-radiative “antenna” with known impedance that you can use to test your RF circuit without radiating. For radio work, you usually just need a 50-ohm resistor that is non-inductive (at least at the frequencies you are interested in) and that can dissipate the amount of power you’ll expect it to handle (at least for a short time). [VO1PWF] wanted a dummy load and built his own.
CantennaThe Cantenna (not the Pringle’s kind; see left) was a famous dummy load design when Heathkit was in business. It was a single carbon rod immersed in a paint can full transformer oil (which we now know was full of dangerous PCBs; and we don’t mean printed circuit boards). [VO1PWF’s] design is a little more practical, using some resistors in parallel (20 1K resistors), a plastic pipe housing, and mineral oil to keep it all cool.

The reason for the parallel resistors is to maximize the power handling capability. The resistors are 3W units, so the dummy load–in theory–can handle 60 watts. Often, high power resistors are wire wound and thus have a good bit of parasitic inductance that makes the dummy load reactive (not a good thing since that makes the load impedance vary by frequency). They do make non-inductive wire wound resistors, but these aren’t truly non-inductive. The wire winds in two different directions, so the inductance tends to cancel out. We wouldn’t trust them to be a pure resistance in a high-power dummy load design.

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SDR Pan Adapter

Ham radio operators have a long history of using pan adapters to visualize an entire range of the radio spectrum. Traditionally, an adapter was essentially a spectrum analyzer that shows a trace where the X-axis is the frequency, and the Y-axis shows the signal strength at any particular frequency. You can quickly find either busy frequencies or empty frequencies at a glance.

Although the pan adapter has been around since the 1930’s, they aren’t as common as you’d think with regular analog radios. However, if you’ve used an SDR (Software Defined Radio), a spectrum display is par for the course. [Mehdi Asgari] did what a lot of hams have been doing lately: he married an SDR and his traditional receiver to provide a great pan adapter with very little effort.

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Bouncing Radio Off of Airplanes

Amateur radio operators are always trying some new stunt or other. It’s like they’ve got something to prove. Take Aircraft scatter for instance: the idea is to extend your radio’s range by bouncing it directionally off of overhead airplanes.

Radio signals travel in straight lines, which is a bummer because the Earth (despite what you’ve heard) is round. Inevitably, if you want to talk to someone far enough away, they’re over a hill. We’ve covered various oddball propagation methods recently, so if you don’t know about moonbounce, you’ve got some background reading to do. But airplane scatter was new to us.

Actually pulling it off requires knowing where the airplanes are, of course. To do so, you could simply look up the aircraft in your target area on the web, using something like FlightRadar24, but where’s the fun in that? There’s also the possibility of tracking local aircraft yourself using RTL-SDR if you’re feeling hard core.

The rest is just details. Hams [Rex Moncur (VK7MO)] and [David Smith (VK3HZ)], for instance, got 10 GHz signals to skip off airplanes over 842 km (PDF). If you’re an old-school ham operator, you’re double-checking the “gigahertz”, but it’s not a mistake. It’s tremendously impressive that these guys got a link over such a long distance using only 10 watts — but note that they’re doing it with highly directive dishes, and telescopes to aim them.

Not to discourage you from trying this at home, but there are all sorts of difficulties that you’ll encounter when you do. Airplanes moving perpendicular to the path between sender and receiver will Doppler-shift the signal, and there’s still quite a chunk of atmosphere to get the signal through. Finally, although airplanes look pretty big when they’re on the ground, they’re actually tiny when they’re up in the sky at 35,000 ft and 500 miles away; you’re bouncing your signal off of a small target.

The good news? People like [W3SZ] are sharing their well-documented results, and at least it’s 20dB easier than bouncing signals off the moon!

Thanks [Martin] for the tip!