Hackaday Links: February 9, 2025

February 9, 2025 by Dan Maloney 15 Comments

January 9 ended up being a very expensive day for a Culver City, California man after he pleaded guilty to recklessly operating a drone during the height of the Pacific Palisades wildfire. We covered this story a bit when it happened (second item), which resulted in the drone striking and damaging the leading edge of a Canadian “Super Scooper” plane that was trying to fight the fire. Peter Tripp Akemann, 56, admitted to taking the opportunity to go to the top of a parking garage in Santa Monica and launching his drone to get a better view of the action to the northwest. Unfortunately, the drone got about 2,500 meters away, far beyond visual range and, as it turns out, directly in the path of the planes refilling their tanks by skimming along the waters off Malibu. The agreement between Akemann and federal prosecutors calls for a guilty plea along with full restitution to the government of Quebec, which owns the damaged plane, plus the costs of repair. Akemann needs to write a check for $65,169 plus perform 150 hours of community service related to the relief effort for the fire’s victims. Expensive, yes, but probably better than the year in federal prison such an offense could have earned him.

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Vintage Crystal Radio Draws The Waves

August 7, 2024 by Al Williams 10 Comments

The classic crystal radio was an oatmeal box with some wire and a few parts. [Michael Simpson] has something very different. He found an assembled Philmore “selective” radio kit. The simple kit had a coil, a germanium diode, and a crystal earphone.

We were sad when [Michael] accidentally burned a part of the radio’s coil. But–well–in the end, it all worked out. We’ll just say that and let you watch for yourself. The radio is simplicity itself, built on a wooden substrate with a very basic coil and capacitor tuned circuit. Continue reading “Vintage Crystal Radio Draws The Waves” →

Hackaday Links: July 14, 2024

July 14, 2024 by Dan Maloney 11 Comments

We’ve been going on at length in this space about the death spiral that AM radio seems to be in, particularly in the automotive setting. Car makers have begun the process of phasing AM out of their infotainment systems, ostensibly due to its essential incompatibility with the electronics in newer vehicles, especially EVs. That argument always seemed a little specious to us, since the US has an entire bureaucracy dedicated to making sure everyone works and plays well with each other on the electromagnetic spectrum. The effort to drop AM resulted in pushback from US lawmakers, who threatened legislation to ensure every vehicle has the ability to receive AM broadcasts, on the grounds of its utility in a crisis and that we’ve spent billions ensuring that 80% of the population is within range of an AM station.

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Radio Frequency Burns, Flying A Kite, And You

April 21, 2024 by Lewin Day 22 Comments

Most hams can tell you that it’s possible to get a nasty RF burn if you accidentally touch an antenna while it’s transmitting. However, you can also cop a nasty surprise on the receiving end if you’re not careful, as explained in a video from [Grants Pass TV Repair].

*It’s hard to see in a still image, but the RF burns from the kite antenna actually generate a little puff of smoke on contact.*

An experiment was used to demonstrate this fact involving a kite and a local AM broadcaster. A simple calculation revealed that an antenna 368 feet and 6 inches long would be resonant with the KAJO Radio signal at 1.270 MHz. At half the signal’s wavelength, an antenna that long would capture plenty of energy from the nearby broadcast antenna.

Enter the kite, which served as a skyhook to loft an antenna that long. With the wire in the air picking up a strong signal from the AM radio tower, it was possible to get a noticable RF burn simply by touching the end of the antenna.

The video explains that this is a risky experiment, but not only because of the risk of RF burn itself. It’s also easy to accidentally get a kite tangled in power lines, or to see it struck by lightning, both of which would create far greater injuries than the mild RF burn seen in the video. In any case, even if you know what you’re doing, you have to be careful when you’re going out of your way to do something dangerous in the first place.

AM radio towers aren’t to be messed with; they’ve got big power flowing. Video after the break.

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AM Radio Broadcast Uses Phasor To Let Eight Towers Spray One Big Signal

April 20, 2024 by Lewin Day 8 Comments

If you’re in the commercial AM radio business, you want to send your signal as far and wide as possible. More listeners means you can make more ad revenue, after all. [Jeff Geerling] recently visited a tower site for WSDZ-AM, which uses a full eight towers to broadcast its 20kW AM signal. To do that, it needs a phasor to keep everything in tune. Or, uh… phase.

The phasor uses a bunch of variable inductors and capacitors to manage the phase of the signal fed to each tower. Basically, by varying the phase of the AM signal going to each of the 8 transmitter towers, it’s possible to tune the directionality of the tower array. This allows the station to ensure it’s only broadcasting to the area it’s legally licensed to do so.

The tower array is also configured to broadcast slightly differently during the day and at night to account for the differences in propagation that occur. A certain subset of the 8 towers are used for the day propagation pattern, while a different subset is used to shape the pattern for the night shift. AM signals can go far farther at night, so it’s important for stations to vary their output to avoid swamping neighbouring stations when the sun goes down.

[Jeff’s] video is a great tour of a working AM broadcast transmitter. If you’ve ever wondered about the hardware running your local commercial station, this is the insight you’re looking for. AM radio may be old-school, but it continues to fascinate us to this day. Video after the break.

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How To Operate A 500KW Transmitter

January 13, 2024 by Al Williams 31 Comments

Crosley was a famous name in radio for more than one reason. The National VOA Museum of Broadcasting has a video telling [Powel Crosley Jr.’s] story, and the story behind the 500 kW WLW transmitter. WLW was an AM broadcast station often called the nation’s channel since its signal covered most of the United States. The first Crosley station was identified at 8CR, running 20 watts from [Crosley’s] living room. Quite a modest start! By 1922, he had moved to his family business location along with 500 watts of output. Over the years, WLW got more powerful until it was finally a 500 kW giant.

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Hackaday Links: August 27, 2023

August 27, 2023 by Dan Maloney 26 Comments

We mentioned last week how robotaxi provider Cruise was having a no-good, very bad week, after one of their driverless taxis picked a fight with a semi, and it was revealed that amorous San Franciscans were taking advantage of the privacy afforded by not having a driver in the front seat. It appears that we weren’t the only ones to notice all the bad news, since California’s Department of Motor Vehicles issued an order to the company to cut its robotaxi fleet in half. The regulatory move comes after a recent Cruise collision with a fire truck, which injured a passenger in the taxi. Curiously, the DMV order stipulates that Cruise can only operate 50 vehicles during the day, while allowing 150 vehicles at night. We’d have thought the opposite would make more sense, since driving at night is generally more difficult than during daylight hours. But perhaps the logic is that the streets are less crowded at night, whereas daytime is a more target-rich environment.

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