Radio Hacks

1376 Articles

2023 Hackaday Supercon: One Year Of Progress For Project Boondock Echo

November 7, 2024 by 2 Comments

Do you remember the fourth-place winner in the 2022 Hackaday Prize? If it’s slipped your mind, that’s okay—it was Boondock Echo. It was a radio project that aimed to make it easy to record and playback conversations from two-way radio communications. The project was entered via Hackaday.io, the judges dug it, and it was one of the top projects of that year’s competition.

The project was the brainchild of Mark Hughes and Kaushlesh Chandel. At the 2023 Hackaday Supercon, Mark and Kaushlesh (KC) came back to tell us all about the project, and how far it had come one year after its success in the 2022 Hackaday Prize.

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Random Wire Antenna Uses No Wire

November 5, 2024 by 40 Comments

Ideally, if you are going to transmit, you want a properly-tuned resonant antenna. But, sometimes, it isn’t practical. [Ham Radio Rookie] knew about random wire antennas but didn’t want a wire antenna. So, he took carbon fiber extension poles and Faraday tape and made a “random stick” antenna. You can check it out in the video below.

We aren’t sure what normal people are doing with 7-meter-long telescoping poles, but — as you might expect — the carbon fiber is not particularly conductive. That’s where the tape comes in. Each section gets some tape, and when you stretch it out, the tape lines up.

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Humble Television Tubes Make An FM Regenerative Radio

November 4, 2024 by 10 Comments

The regenerative radio is long-ago superseded in commercial receivers, but it remains a common project for electronics or radio enthusiasts seeking to make a simple receiver. It’s most often seen for AM band receivers or perhaps shortwave ham band ones, but it’s a circuit which also works at much higher frequencies. [Perian Marcel] has done just this, with a regenerative receiver for the FM broadcast band.

The principle of a regenerative receiver is that it takes a tuned radio frequency receiver with a wide bandwidth and poor performance, and applies feedback to the point at which the circuit is almost but not quite oscillating. This has the effect of hugely increasing the “Q”, or quality factor of the receiver, giving it much more sensitivity and a narrow bandwidth. They’re tricky to tune but they can give reasonable performance, and they will happily slope-demodulate an FM transmission.

This one uses two tubes from consumer grade TV receivers, the “P” at the start of the part number being the giveaway for a 300mA series heater chain. The RF triode-pentode isn’t a radio part at all, instead it’s a mundane TV field oscillator part pushed into service at higher frequencies, while the other triode-pentode serves as an audio amplifier. The original circuit from which this one is adapted is available online, All in all it’s a neat project, and a reminder that exotic parts aren’t always necessary at higher frequencies. The video is below the break.

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A Lesson In RF Design Thanks To This Homebrew LNA

November 4, 2024 by 7 Comments

If you’re planning on working satellites or doing any sort of RF work where the signal lives down in the dirt, you’re going to need a low-noise amplifier. That’s typically not a problem, as the market is littered with dozens of cheap options that can be delivered in a day or two — you just pay your money and get to work. But is there a case to be made for rolling your own LNA?

[Salil, aka Nuclearrambo] thinks so, and he did a nice job showing us how it’s done. The first step, as always, is to define your specs, which for [Salil] were pretty modest: a low noise figure, moderate gain, and good linearity. He also wanted a bandpass filter for the 2-meter amateur radio band and for weather satellite downlinks, and a bias-tee to power the LNA over the coax feedline. The blog post has a detailed discussion of the electrical design, plus some good tips on PCB design for RF applications. We also found the discussion on bias-tee design helpful, especially for anyone who has ever struggled with the idea that RF and DC can get along together on a single piece of coax. Part 2 concentrates on testing the LNA, mostly using hobbyist-grade test gear like the NanoVNA and tiny SA spectrum analyzer. [Salil]’s tests showed the LNA lived up to the design specs and more, making it more than ready to put to work with an RTL-SDR.

Was this more work than buying an LNA? Absolutely, and probably with the same results. But then again, what’s to learn by just getting a pre-built module in the mail?

GNSS Reception With Clone SDR Board

November 3, 2024 by 14 Comments

We love seeing the incredible work many RF enthusiasts manage to pull off — they make it look so easy! Though RF can be tricky, it’s not quite the voodoo black art that it’s often made out to be. Many radio protocols are relatively simple and with tools like gnuradio and PocketSDR you can quickly put together a small system to receive and decode just about anything.

[Jean-Michel] wanted to learn more about GNSS and USB communication. Whenever you start a project like this, it’s a good idea to take a look around at existing projects for designs or code you can reuse, and in this case, the main RF front-end board is taken from the PocketSDR project. This is then paired with a Cypress FX2 development board, and he re-wrote almost all of the PocketSDR code so that it would compile using sdcc instead of the proprietary Keil compiler. Testing involved slowly porting the code while learning about using Python 3 to receive data over USB, and using other equipment to simulate antenna diversity (using multiple antennas to increase the signal-to-noise ratio): Continue reading “GNSS Reception With Clone SDR Board” →

Few Things Are Cheaper Than This Antenna

October 31, 2024 by 44 Comments

As far as hobbies go, ham radio tends to be on the more expensive side. A dual-band mobile radio can easily run $600, and a high-end HF base station with the capability of more than 100 watts will easily be in the thousands of dollars. But, like most things, there’s an aspect to the hobby that can be incredibly inexpensive and accessible to newcomers. Crystal radios, for example, can be built largely from stuff most of us would have in our parts drawers, CW QRP radios don’t need much more than that, and sometimes even the highest-performing antennas are little more than two lengths of wire.

For this specific antenna, [W3CT] is putting together an inverted-V which is a type of dipole antenna. Rather than each of the dipole’s legs being straight, the center is suspended at some point relatively high above ground with the two ends closer to the earth. Dipoles, including inverted-Vs, are resonant antennas, meaning that they don’t need any tuning between them and the radio so the only thing needed to match the antenna to the feed line is a coax-to-banana adapter. From there it’s as simple as attaching the two measured lengths of wire for the target band and hoisting the center of the antenna up somehow. In [W3CT]’s case he’s using a mast which would break the $8 budget, but a tree or building will do just as well.

The video on the construction of this antenna goes into great detail, so if you haven’t built a dipole yet or you’re just getting started on your ham radio journey, it’s a great place to get started. From there we’d recommend checking out an off-center-fed dipole which lets a dipole operate efficiently on multiple bands instead of just one, and for more general ham radio advice without breaking the bank we’d always recommend the $50 Ham series.

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Homebrew Sferics Receiver Lets You Tune Into Earth Music

October 30, 2024 by 10 Comments

It probably comes as little surprise that our planet is practically buzzing with radio waves. Most of it is of our own making, with cell phones, microwaves, WiFi, and broadcasts up and down the spectrum whizzing around all the time. But our transmissions aren’t the only RF show in town, as the Earth itself is more than capable of generating radio signals of its own, signals which you can explore with a simple sferics receiver like this one.

If you’ve never heard of sferics and other natural radio phenomena, we have a primer to get you started. Briefly, sferics, short for “atmospherics,” are RF signals in the VLF range generated by the millions of lightning discharges that strike the Earth daily. Tuning into them is a pretty simple proposition, as [DX Explorer]’s receiver demonstrates. His circuit, which is based on a design by [K8TND], is just a single JFET surrounded by a few caps and resistors, plus a simple trap to filter out the strong AM broadcast signals in his area. The output of the RF amplifier goes directly into an audio amp, which could be anything you have handy — but you risk breaking [Elliot]’s heart if you don’t use his beloved LM386.

This is definitely a “nothing fancy” build, with the RF section built ugly style on a scrap of PCB and a simple telescopic whip used for an antenna. Tuning into the Earth’s radio signals does take some care, though. Getting far away from power lines is important, to limit AC interference. [DX Explorer] also found how he held the receiver was important; unless he was touching the ground plane of the receiver, the receiver started self-oscillating. But the pips, crackles, and pings came in loud and clear on his rig; check out the video below for the VLF action.

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