Radio Hacks

1394 Articles

Atomic Antenna Uses Lasers

October 21, 2023 by 12 Comments

If you think about it, an antenna is nothing more than a radio frequency energy sensor, or — more precisely — a transducer. So, it shouldn’t be a surprise that there could be different ways to sense RF that would work as an antenna. A recent paper in Applied Physics Letters explains an atomic antenna comprised of a rubidium vapor cell.

The interesting thing is that the antenna has no electrical components in the antenna, and can be located far away from the actual receiver. Instead of coax cables, the signal is read with a laser.

Continue reading “Atomic Antenna Uses Lasers” →

Junk Bin Cyberdish Turns You Into The Satellite Tracker

October 21, 2023 by 3 Comments

The good thing about listening in on satellites is that they tend to beam down all kinds of juicy information from their lofty perches. The bad thing about satellites is that to stay in those orbits, they’ve got to be moving really fast, and that means that you’ve got to track them if you want to keep a nice consistent signal during a pass. And that can lead to all sorts of complexity, with motorized two-axis mounts and fancy tracking software.

Or does it? Not if you’re willing to act as the antenna mount, which is the boat [Gabe] from the saveitforparts channel on YouTube recently found himself in when searching for L-band signals from the GOES satellite. His GOES setup uses a 30″ (0.8 m) dish repurposed from a long-range wireless networking rig. Unfortunately, the old security camera pan-tilt unit it was mounted on wasn’t quite up to satellite tracking duty, so [Gabe] pulled the dish off and converted it to manual tracking.

With a freshly wound helical antenna and a SAWbird LNA at the focal point, the dish proved to be pretty easy to keep on track manually, while providing quite the isometric workout. Aiming was aided by an app called Stellarium which uses augmented reality to point out objects in the night sky, and a cheap tablet computer was tasked with running SDR++ and capturing data. Sadly, neither of these additions brought much to the party, with the latter quickly breaking and the former geared more toward stargazing than satellite snooping. But with some patience — and some upper-body strength — [Gabe] was able to track GOES well enough with the all-in-one “cyberdish” to get some usable images. The whole saga is documented in the video after the break.

Kudos to [Gabe] for showing us what can be accomplished with a little bit of junk and a lot of sticktoitiveness. He promises that a legit two-axis mount is in the works, so we’ll be on the lookout for that. We’ve seen a few of those before, and [Chris Lott] did a great overview of satellite tracking gear a while back, too.

Continue reading “Junk Bin Cyberdish Turns You Into The Satellite Tracker” →

This Packable Ham Radio Antenna Is Made From Nothing But Tape

October 13, 2023 by 47 Comments

On today’s episode of “Will It Antenna?”, [Ben Eadie (VE6SFX)] designs and tests an antenna made entirely of tape, and spoiler alert — it works pretty well.

By way of background, the basic design [Ben] uses here is known as a J-pole, a popular “my first antenna” design for amateur radio operators looking to go beyond the stock whip antenna that comes with that cheap handy-talkie you just can’t resist buying as soon as you get your license. Usually, though, hams will build their J-poles from rigid materials, copper water pipe being a typical choice. Copper has the advantage of being easily sourced, and also results in a self-supporting, weather-resistant antenna that’s easy to mount outdoors. However, copper is getting to be egregiously expensive, and a couple of meters of water pipe isn’t exactly amenable to portable operation, if that’s your jam.

To solve those problems, [Ben] decided to keep his copper use to a minimum with a roll of copper foil tape. He doesn’t provide any specs on the tape, but it looks like it’s about 6 mm (1/4″) wide and judging by a quick Amazon search, probably goes for about $10 a roll. He starts the build with a couple of strips of plain old duck tape — we’ve already had the “duck vs. duct” argument — laid out with the sticky sides together. The copper foil is applied to the duck tape backing using dimensions from any of the J-pole calculators available online. Dimensions are critical to getting good performance from a J-pole, and this is where [Ben]’s tape design shines. Element too long? No problem, just peel up a bit and tear some off. Did you go too far and make an element too short? Easy — just stick on an extension piece of foil. Tuning the location of the feedline connection was a snap, too, with movable terminals held in place with magnets.

Once everything was tuned up, [Ben] soldered down the feed points and covered the foil with a protective layer of duck tape. The antenna performed swimmingly, and aside from costing almost nothing to build, it weighs very little, rolls up to fit in a pack for field operations, and can easily be hoisted into a tree for better coverage. Looks like we’ll be putting in an order for some copper tape and building one of these too. Continue reading “This Packable Ham Radio Antenna Is Made From Nothing But Tape” →

National Research Council laboratories in Ottawa

Canada Abruptly Ends Official Time Signal

October 13, 2023 by 47 Comments

In a sudden move that was noted not only by Canadian media, but also international media channels, the National Research Council Time Signal that was broadcast by Canadian Broadcasting Corporation (CBC) on CBC Radio One since November 5 1939 was turned off on October 9th, after eighty-four years, one world war, countless generations, and the rise of modern technology. Although perhaps obsolete by today’s standards, this 15 to 60 second long broadcast at 13:00 Eastern Time every single day has been a constant in the life of Canadians, whether they tuned into local radio, or (increasingly) via Internet radio.

The NRC Time Signal consisted out of a series of 800 Hz sinewave ‘beeps’ followed by a second-long signal to indicate the top of the hour. Back in the day this was extremely useful to sync one’s clocks, watches and other time-keeping devices to. Yet between the transmission delays caused by Internet radio and the increased availability of NTP and other time sources on modern-day devices, the signal’s main use appears to have become a nostalgic reminder of what once was a constant of each and every day.

In this regard the public response to the rather unceremonious decommissioning without prior announcement was rather predictable. After all, even if it wasn’t that useful, why throw out something that is more recognizable than any other radio jingle for generations of Canadians?

Top image: National Research Council laboratories in Ottawa.

Antennas Can Be A Total Mystery

October 10, 2023 by 14 Comments

The real action in the world of ham radio is generally in the high frequency bands. Despite the name, these are relatively low-frequency bands by modern standards and the antenna sizes can get a little extreme. After all, not everyone can put up an 80-meter dipole, but ham radio operators have come up with a number of interesting ways of getting on the air anyway. The only problem is that a lot of these antennas don’t seem as though they should work half as well as they do, and [MIKROWAVE1] takes a look back on some of the more exotic radiators.

He does note that for a new ham radio operator it’s best to keep it simple, beginning work with a dipole, but there are still a number of options to keep the size down. A few examples are given using helically-wound vertical antennas or antennas with tuned sections of coaxial cable. From there the more esoteric antennas are explored, such as underground antennas, complex loops and other ways of making a long wire fit in a small space, and even simpler designs like throwing a weight with a piece of wire attached out the window of an apartment building.

While antenna theory is certainly a good start for building antennas, a lot of the design of antennas strays into artistry and even folklore as various hams will have successes with certain types and others won’t. It’s not a one-size-fits-all situation so the important thing is to keep experimenting and try anything that comes to mind as long as it helps get on the air. A good starting point is [Dan Maloney]’s $50 Ham Guide series, and one piece specifically dealing with HF antennas.

Continue reading “Antennas Can Be A Total Mystery” →

Wok Your Way To The Center Of The Galaxy

October 6, 2023 by 14 Comments

The round bottom of a proper wok is the key to a decent stir fry, but it also makes it hard to use on traditional Western stoves. That’s why many woks end up in a dark kitchen cabinet, unused and unloved. But wait; it turns out that the round bottom of a wok is the perfect shape for gathering something else — radio waves, specifically the 21-cm neutral hydrogen emissions coming from the heart of our galaxy.

Turning a wok into an entry-level radio telescope doesn’t appear to be all that hard, at least judging by what [Leo W.H. Fung] et al detail in their paper (PDF) on “WTH” or “Wok the Hydrogen.” Aside from the wok, which serves as the main reflector, you’ll need a bit of coaxial cable and some stiff copper wire to fashion a small dipole antenna and balun, plus some plastic tubing to support it at the focal point of the reflector. Measuring the wok’s shape and size, which in turn determines its focal point, is probably the hardest part of the build; luckily, the paper includes tips on doing just that. The authors address the controversy of parabolic versus spherical reflectors and arrive at the conclusion that for a radio telescope fashioned from a wok, it just doesn’t matter.

As for the signal processing chain, WTH holds few surprises. A Nooelec Sawbird+ H1 acts as preamp and filter for the 1420-MHz hydrogen line signal, which feeds into an RTL-SDR dongle. Careful attention is paid to proper grounding and shielding to keep the noise floor as low as possible. Mounting the antenna is a decidedly ad hoc affair, and aiming is as simple as eyeballing various stars near the center of the galactic plane — no need to complicate things.

Performance is pretty good: WTH measured the recession velocity of neutral hydrogen to within 20 km/s, which isn’t bad for something cobbled together from scrap. We’ve seen plenty of DIY hydrogen line observatories before, but WTH probably wins the “get on the air tonight” award.

Thanks to [Heinz-Bernd Eggenstein] for the tip.

A software-defined radio system in a 3D-printed case with a 7" display and an array of knobs and switches

Hackaday Prize 2023: A Software-Defined Radio With Real Knobs And Switches

September 25, 2023 by 16 Comments

When cheap digital TV dongles enabled radio enthusiasts to set up software defined radio (SDR) systems at almost zero cost, it caused a revolution in the amateur radio world: now anyone could tune in to any frequency, with any modulation type, by just pointing and clicking in a computer program. While this undoubtably made exploring the radio waves much more accessible, we can imagine that some people miss the feeling of manipulating physical buttons on a radio while hunting for that one faint signal in a sea of noise. If you’re one of those people, you’re in luck: [Kaushlesh C.] has built a portable, self-contained SDR system with real knobs and switches, called SDR Dock 1.0. Continue reading “Hackaday Prize 2023: A Software-Defined Radio With Real Knobs And Switches” →