radio

532 Articles

Traditional Analogue And An FPGA Make This Junkbox HF Receiver A Bit Special

August 20, 2021 by 2 Comments

We will have all at some point seen a fascinating project online, only to find not enough information to really appreciate and understand it. Such a project came [Bill Meara]’s way over at the SolderSmoke podcast, and he was fortunately able to glean more from its creator. What [Tom] had made from junkbox parts was a fairly traditional analogue receiver for the 20m amateur band which would be quite an achievement in itself, but what makes it special is its use of an FPGA to augment the analogue tuning.

A traditional analogue radio has a local oscillator which is mixed with the signal from the antenna, and an intermediate frequency of the difference between oscillator and desired signal is filtered from the result and amplified. The oscillator on older receivers would have used a free running tuned circuit, while a newer device might use a phase-locked loop to derive a stable frequency from a crystal.

What [Tom]’s receiver does is take a free-running traditional receiver and use the FPGA as a helper. It has a frequency meter that drives the display, but it also uses the measured figure to adjust the oscillator and keep it on frequency. It has two modes; while tuning it’s a traditional analogue receiver, but when left alone the FPGA stops it drifting. We like it, it’s definitely a special project.

We’ve featured a lot of radio receivers over the years, and this certainly isn’t the only one that’s a bit unconventional.

Rare Radio Receiver Teardown

July 30, 2021 by 15 Comments

We’ll admit we haven’t heard of the AGS-38, it reminds us of the shortwave receivers of our youth, and it looks like many that were made “white label” by more established (and often Japanese) companies. [Jeff] found a nice example of this Canadian radio and takes it apart for our viewing pleasure. He also found it was very similar to a Layfayette receiver, also made in Japan, confirming our suspicions.

The radio looks very similar to an Eico of the same era — around the 1960s. With seven tubes, radios like this would soon be replaced by transistorized versions.

Continue reading “Rare Radio Receiver Teardown” →

A Cheap Dipole Antenna From An Extension Cord

July 16, 2021 by 12 Comments

Dipoles are a classic builder’s antenna, after all they are usually little more than two pieces of wire and a feedline. But as [Rob] shows us in the video below, there are a few things to consider.

The first thing is where to get the wire. A damaged extension cord donated the wire. That’s actually an interesting idea because you get multiple wires the same length inside the extension cord.  Continue reading “A Cheap Dipole Antenna From An Extension Cord” →

New Video Series: Learning Antenna Basics With Karen Rucker

July 15, 2021 by 21 Comments

We don’t normally embrace the supernatural here at Hackaday, but when the topic turns to the radio frequency world, Arthur C. Clarke’s maxim about sufficiently advanced technology being akin to magic pretty much works for us. In the RF realm, the rules of electricity, at least the basic ones, don’t seem to apply, or if they do apply, it’s often with a, “Yeah, but…” caveat that’s sometimes hard to get one’s head around.

Perhaps nowhere does the RF world seem more magical than in antenna design. Sure, an antenna can be as simple as a straight piece or two of wire, but even in their simplest embodiments, antennas belie a complexity that can really be daunting to newbie and vet alike. That’s why we were happy to recently host Karen Rucker’s Introduction to Antenna Basics course as part of Hackaday U.

The class was held over a five-week period starting back in May, and we’ve just posted the edited videos for everyone to enjoy. The class is lead by Karen Rucker, an RF engineer specializing in antenna designs for spacecraft who clearly knows her business. I’ve watched the first video of the series and so far and really enjoy Karen’s style and the material she has chosen to highlight; just the bit about antenna polarization and why circular polarization makes sense for space communications was really useful. I’m keen to dig into the rest of the series playlist soon.

The 2021 session of Hackaday U may be wrapped up now, but fear not — there’s plenty of material available to look over and learn from. Head over to the course list on Hackaday.io, pick something that strikes your fancy, and let the learning begin!

Continue reading “New Video Series: Learning Antenna Basics With Karen Rucker” →

You Can’t Fix What You Can’t Measure

July 10, 2021 by 13 Comments

Last year, as my Corona Hobby™, I took up RC plane flying. I started out with discus-launched gliders, and honestly that’s still my main love, but there’s only so much room for hackery in planes that are designed to be absolutely minimum weight and maximum performance; these are the kind of planes that notice an extra half gram in the tail. So I’ve also built a few crude workhorse planes — the kind of things that you could slap a 60 g decade-old GoPro on and it won’t even really notice. Some have ended their lives in trees, but most have been disassembled and reincarnated — the electronics live on in the next body.

The journey has been really fun. I’ve learned about aerodynamics, gotten an excuse to put together a 4-axis hot-wire CNC styrofoam cutter, and covered everything in sight with carbon fiber tow, which is cheaper than you might think but makes the plane space-age. My current workhorse has bolted on an IMU, GPS, and a minimal Ardupilot setup, though I have yet to really put it through its paces. What’s holding me back is the video link — it just won’t work reliably further than a few hundred meters, and I certainly don’t trust it to get out of line-of-sight.

My suspicion is that the crappy antennas I have are holding me back, which of course is an encouragement to DIY, but measuring antennas in the 5.8 GHz band is tricky. I’d love to just be able to buy one of the cheap vector analyzers that we’ve covered in the past — anyone can make an antenna when they can see what they’re doing — but they top out at 2.4 GHz or lower. No dice. I’m blind in 5.8 GHz.

Of course, I do have one way in, and that’s tapping into the received signal strength indicator (RSSI) of a dedicated 5.8 GHz receiver, and just testing antennas out in practice, but that only gives a sort of loose better-worse indication. More capacitance or more inductance? Plates closer together or further apart? Try it out and see, I guess, but it’s time-consuming.

Moral of the story: don’t take measurement equipment for granted. Imagine trying to build an analog circuit without a voltmeter, or to debug something digital without a logic probe. Sometimes the most important tool is the one that lets you see the problem in the first place.

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Balloon Antenna Doesn’t Need A Tower

June 11, 2021 by 20 Comments

What do you do with floral wire and balloons from Dollar Tree? If you are [Ham Radio Crash Course], you make a ham radio antenna. Floral wire is conductive, and using one piece as a literal sky hook and the other as a ground wire, it should do something. He did use, as you might expect, a tuner to match the random wire length.

The first attempt had too few balloons and too much wind. He eventually switched to a non-dollar store helium tank. That balloon inflates to about 36 inches and appears to have plenty of lift. It looks like by the end he was using two of them.

Continue reading “Balloon Antenna Doesn’t Need A Tower” →

Radio Build Goes Outside The Box

June 3, 2021 by 4 Comments

It’s easy to get caught up in a build and forget that the final version usually needs some sort of enclosure, especially things with sensitive electronics in them. The [Director of Legal Evil] at the LVL1 Louisville Hackerspace notes as much in his recent radio build. It seems as though the case was indeed an afterthought, but rather than throwing it in a nondescript black project enclosure it was decided to turn the idea of a project enclosure itself inside-out.

The radio build is based on an SI4732 radio receiver which is a fairly common radio module and is easily adaptable. It needs a microcontroller to run though, so a Maple STM32 platform was chosen to do all of the heavy lifting. The build includes a screen, some custom analog controls, and a small class D audio amplifier, but this is the point it begins to earn its name: the Chaos Radio. While playing around with the project design in CAD, a normal design seemed too bland so one was chosen which makes the radio look like the parts are exploding outward from what would have been a more traditional-style enclosure.

While the project includes a functioning radio receiver, we have to complement the creator for the interesting display style for this particular set of hardware. It can get boring designing the same project enclosures time after time, so anything to shake things up is often welcomed especially when it puts all of the radio components on display like this. In fact, it’s reminiscent of some of [Dmitry]’s projects, an artist known for deconstructing various common household appliances like this CD Player.

Thanks to [Jose] for the tip!