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153 Articles

Name That Unknown RF Signal With A Little FFT Magic

February 11, 2020 by 27 Comments

Time was once that the amateur radio bands were an aurally predictable place. Spinning the dial up and down the bands, one heard familiar sounds – the staccato of Morse, the [Donald Duck] of sideband voice transmissions, and the occasional flute-like warble of radioteletype signals. Now, the ham bands are full of exotic signals encoding all manner of digital signals, each one with a unique sound and unique demodulation needs. What’s a ham to do?

Help is on the way. [José Carlos Rueda] has made progress toward automatically classifying unknown signals by modifying a Shazam-like app. Shazam is a popular smartphone app that listens to a few seconds of a song, creates an audio fingerprint of it, and searches a massive database of songs for a match. [Rueda] used a homebrew version of the app to search a SQL-lite database of audio fingerprints populated not with a playlist of popular music, but with samples from every known signal type in the Signal Identification Wiki. The database contains hashes for an FFT of each sample, which can be easily searched. With a five to ten second sample of a signal, captured either live over a microphone or from a recording,  he is able to identify the signal automatically.

Whether it be the weird, dissonant wail of PSK-31 or the angry buzzing of PACTOR, the goings-on across the bands no longer have to remain a mystery. We really like the idea here, and wonder if it can be expanded upon to visually decode signals based on their waterfall signatures using TensorFlow. There are some waterfall examples in [Danie Conradie]’s excellent article on RF modulation that could get you started.

[via RTL-SDR.com]

Keeping Ham Radio Relevant Hack Chat

February 3, 2020 by 69 Comments

Join us on Wednesday, February 5 at noon Pacific for the Keeping Ham Radio Relevant Hack Chat with Josh Nass!

It may not seem like it, but amateur radio is fighting a two-front war for its continued existence. On the spectrum side, hams face the constant threat that the precious scraps of spectrum that are still allocated to their use will be reclaimed and sold off to the highest bidder as new communication technologies are developed. On the demographic side, amateur radio is aging, with fewer and fewer young people interested in doing the work needed to get licensed, with fewer still having the means to get on the air.

Amateur radio has a long, rich history, but gone are the days when hams can claim their hobby is sacrosanct because it provides communications in an emergency. Resting on that particular laurel will not win the hobby new adherents or help it hold onto its spectrum allocations​, so Josh Nass (KI6NAZ) is helping change the conversation. Josh is an engineer and radio amateur from Southern California who runs Ham Radio Crash Course​, a YouTube channel dedicated to getting people up to speed on ham radio. Josh’s weekly livestreams and his video reviews of ham radio products and projects show a different side of the World’s Greatest Hobby, one that’s more active (through events like “Summits on the Air​​”) and focused on digital modes that are perhaps more interesting and accessible to new hams.

Join us on the Hack Chat as we discuss how to make ham radio matter in today’s world of pervasive technology. We’ll talk about the challenges facing amateur radio, the fun that’s still to be had on the air even when the bands are dead like they are now (spoiler alert: they’re not really), and what we can all do to keep ham radio relevant.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, February 5 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about. Continue reading “Keeping Ham Radio Relevant Hack Chat” →

The RFI Hunter: Looking For Noise In All The Wrong Places

January 15, 2020 by 22 Comments

Next time you get a new device and excitedly unwrap its little poly-wrapped power supply, remember this: for every switch-mode power supply you plug in, an amateur radio operator sheds a tear. A noisy, broadband, harmonic-laden tear.

The degree to which this fact disturbs you very much depends upon which side of the mic you’re on, but radio-frequency interference, or RFI, is something we should all at least be aware of. [Josh (KI6NAZ)] is keenly aware of RFI in his ham shack, but rather than curse the ever-rising noise floor he’s come up with some helpful tips for hunting down and eliminating it – or at least reducing its impact.

Attacking the problem begins with locating the sources of RFI, for which [Josh] used the classic “one-circuit-at-a-time” approach – kill every breaker in the panel and monitor the noise floor while flipping each breaker back on. This should at least give you a rough idea of where the offending devices are in your house. From there, [Josh] used a small shortwave receiver to locate problem areas, like the refrigerator, the clothes dryer, and his shack PC. The family flat-screen TV proved to be quite noisy too. Remediation techniques include wrapping every power cord and cable around toroids or clamping ferrite cores around them, both on the offending devices and in the shack. He even went so far as to add a line filter to the dryer to clamp down on its unwanted interference.

Judging by his waterfall displays, [Josh]’s efforts paid off, bringing his noise floor down from S5 to S1 or so. It’s too bad he had to take matters into his own hands – it’s not like the FCC and other spectrum watchdogs don’t know there’s a problem, after all.

Continue reading “The RFI Hunter: Looking For Noise In All The Wrong Places” →

Well-Engineered RF Amplifier Powers Ham Radio Contacts

November 7, 2019 by 35 Comments

Typically, amateur radio operators use the minimum power needed to accomplish a contact. That’s just part of being a good spectrum citizen, and well-earned bragging rights go to those who make transcontinental contacts on the power coming from a coin cell. But sometimes quantity has a quality all its own, and getting more power into the ether is what the contact requires. That’s where builds such as this well-engineered 600W broadband RF amplifier come into play.

We’re really impressed with the work that [Razvan] put into this power amp. One of the great joys of being a ham is being able to build your own gear, and to incorporate the latest technology long before the Big Three manufacturers start using it. While LDMOS transistors aren’t exactly new – laterally-diffused MOSFETs have been appearing in RF power applications for decades – the particular parts used for the amp, NXP’s MRF300 power transistors, are pretty new to the market. A pair of the LDMOS devices form the heart of the push-pull amp, as do an array of custom-wound toroids and transformers including a transmission line transformer wound with 17-ohm coax cable. [Razvan] paid a lot of attention to thermal engineering, too, with the LDMOS transistors living in cutouts in the custom PCB so they can mate with a hefty heatsink. Even the heatsink compound is special; rather than the typical silicone grease, he chose a liquid metal alloy called Gallinstan. The video below gives a tour of the amp and shows some tests with impressive results.

Continue reading “Well-Engineered RF Amplifier Powers Ham Radio Contacts” →

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Hackaday Links: September 1, 2019

September 1, 2019 by 10 Comments

The sun may be spotless, but that doesn’t mean it isn’t doing interesting things. A geomagnetic storm is predicted for this weekend, potentially giving those at latitudes where the Northern Lights are not common a chance to see a cosmic light show. According to SpaceWeather.com, a coronal hole, a gap in the sun’s atmosphere that can let the solar wind escape, is about to line up with Earth. The last time this hole was on the Earth-facing side of the sun, the resultant storm gave aurora as far south as Colorado. So if you’re in any of the northern tier states, you might want to find somewhere with dark skies and a good view to the north this weekend.

It’s not only space weather that’s in the news, but weather-weather too. Hurricane Dorian will probably make landfall as a Category 4 storm, probably along Florida’s Atlantic coast, and probably in the middle of the night on Monday. That’s a lot of uncertainty, but one thing’s for sure: amateur radio operators will be getting into the action. The Hurricane Watch Net will activate their net for Dorian on Saturday afternoon at 5:00 PM Eastern time, ready to take reports from stations in the affected area. Not a ham? You can still listen to the live feed once the net activates.

Hams aren’t the only ones getting geared up for Dorian, though. Weather satellite enthusiasts are pointing their SDRs at the sky and grabbing some terrifyingly beautiful pictures of Dorian as it winds up. Some of the downloaded images are spectacular, and if you’ve got an SDR dongle and a couple of pieces of coat hanger wire, you too can spy on Dorian from any number of satellites.

Speaking of which, over on r/RTLSDR, someone has done a little data mining and shown that NOAA 15 is still very much alive. u/amdorj plotted the scan motor current draw and found that it steadily decreased over time, possibly indicating that the bearings aren’t as worn as previously thought. We recently covered the story of the plucky satellite that’s almost two decades past its best-by date; here’s hoping our report on its death was greatly exaggerated.

In one of the weirder bits of marketing we’ve seen lately, NASA decided to name a rock on Mars after septuagenarian rockers The Rolling Stones. The golf ball size rock was blasted about a meter across the Martian landscape when the Mars InSight lander touched down in 2018, leaving a small scar in the dust. The stone had obviously rolled, so phone calls were made and one thing led to another, and before you know it, Robert Downey Jr. is making the announcement before a Stones concert at the Rose Bowl, right in JPL’s backyard. There’s even a cute animation to go along with it. It’s a nice piece of marketing, but it’s not the first time the Stones have been somewhat awkwardly linked to the technology world. We dare you not to cringe.

We’ll finish up today with something not related to space. As Al Williams recently covered, for about fifty bucks you can now score a vector network analyzer (VNA) that will do all sorts of neat RF tricks. The NanoVNA sounds like a great buy for anyone doing RF work, but its low price point and open-source nature mean people are finding all kinds of nifty uses for it. One is measuring the length of coax cables with time-domain reflectometry, or TDR. Phasing antenna arrays? the NanoVNA sounds like the perfect tool for the job.

Clock Radio Receives Upgrade

May 5, 2019 by 8 Comments

Before everyone had a cell phone alarm to wake them up in the mornings, most of us used clock radios that would faithfully sit by our beds for years. You could have either a blaring alarm to wake you up, or be gently roused from slumber by one of your local radio stations. These devices aren’t as commonly used anymore, so if you have one sitting in your parts drawer you can make some small changes and use it to receive radio stations from a little further away than you’d expect.

This Panasonic clock radio from [Ryan Flowers] has several upgrades compared to the old clock radio hardware. For one, it now can receive signals on the 7 and 14 MHz bands (40 and 20 meters). It does this by using separate bandpass filters for each frequency range, controlled by a QRP Labs VFO kit which can switch between the two filters automatically once programmed. The whole thing is powered by 8 AA batteries, true to form with a clock radio from the ’90s.

[Ryan] notes that his first iteration was a little quiet but he’s now able to receive radio stations from as far away from Japan with this receiver. Even without a license, you can make these changes and listen in to stations from all around the world, as long as you don’t start transmitting. If you want to make a small upgrade from this clock radio though, it’s not that hard to get into.

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Es’hail-2: Hams Get Their First Geosynchronous Repeater

March 18, 2019 by 27 Comments

In the radio business, getting the high ground is key to covering as much territory from as few installations as possible. Anything that has a high profile, from a big municipal water tank to a roadside billboard to a remote hilltop, will likely be bristling with antennas, and different services compete for the best spots to locate their antennas. Amateur radio clubs will be there too, looking for space to locate their repeaters, which allow hams to use low-power mobile and handheld radios to make contact over a vastly greater range than they could otherwise.

Now some hams have claimed the highest of high ground for their repeater: space. For the first time, an amateur radio repeater has gone to space aboard a geosynchronous satellite, giving hams the ability to link up over a third of the globe. It’s a huge development, and while it takes some effort to use this new space-based radio, it’s a game changer in the amateur radio community.

Continue reading “Es’hail-2: Hams Get Their First Geosynchronous Repeater” →