transmitter

80 Articles

FM Transmitter Remotely Controlled Via ESP32

October 18, 2024 by 13 Comments

Imagine you’ve got an FM transmitter located some place. Wouldn’t it be mighty convenient if you could control that transmitter remotely? That way, you wouldn’t have to physically attend to it every time you had to change some minor parameters! To that end, [Ricardo Lima Caratti] built a rig to do just that.

The build is based around the QN8066—a digital FM transceiver built into a single chip. It’s capable of transmitting and receiving anywhere from 60 MHz to 108 MHz, covering pretty much all global FM stereo radio bands. [Ricardo] paired this chip with an ESP32 for command and control. The ESP32 hosts an HTTP server, allowing the administration of the FM transmitter via a web browser. Parameters like the frequency, audio transmission mode, and Radio Data Service (RDS) information can be controlled in this manner.

It’s a pretty neat little build, and [Ricardo] demonstrates it on video with the radio transmitting some field day content. We’ve seen some other nifty FM transmitters over the years, too. Video after the break.

Continue reading “FM Transmitter Remotely Controlled Via ESP32” →

Be Your Own DJ With QN8066 And An Arduino Library

August 10, 2024 by 5 Comments

The QN8066 is a fun little FM transmitter chip. It covers the full FM broadcast band and has built-in DSP. You would find this sort of part in car cell phone adapters before every vehicle included Bluetooth or an AUX port.  [Ricardo] has created an Arduino library to bring the QN8066 to the masses.

The chip is rather easy to use – control is handled with a common I2C interface. All the complex parts – Phase Locked Loop (PLL), RF front end, power management, and audio processing are all hidden inside. [Ricardo’s] library makes it even easier to use. One of the awesome features of the 8066 is the fact that it handles Radio Data System (RDS). RDS is the subcarrier datastream that allows FM stations to inject information like song title and artist into the signal. The data is then displayed on your radio screen.

You can find the source to [Ricardo’s] library on GitHub. Using it is as simple as picking it up from the Arduino IDE.

If you are looking for an RDS-enabled radio to test out your QN8066 design, you wouldn’t do too bad with this Gameboy cartridge receiver.

Click through the break for a video from [Ricardo] explaining his QN8066 design. Continue reading “Be Your Own DJ With QN8066 And An Arduino Library” →

A Super-Simple Standalone WSPR Beacon

June 14, 2024 by 26 Comments

We’ve said it before and we’ll say it again: being able to build your own radios is the best thing about being an amateur radio operator. Especially low-power transmitters; there’s just something about having the know-how to put something on the air that’ll reach across the planet on a power budget measured in milliwatts.

This standalone WSPR beacon is a perfect example. If you haven’t been following along, WSPR stands for “weak-signal propagation reporter,” and it’s a digital mode geared for exploring propagation that uses special DSP algorithms to decode signals that are far, far down into the weeds; signal-to-noise ratios of -28 dBm are possible with WSPR.

Because of the digital nature of WSPR encoding and the low-power nature of the mode, [IgrikXD] chose to build a standalone WSPR beacon around an ATMega328. The indispensable Si5351 programmable clock generator forms the RF oscillator, the output of which is amplified by a single JFET transistor. Because timing is everything in the WSPR protocol, the beacon also sports a GPS receiver, ensuring that signals are sent only and exactly on the even-numbered minutes. This is a nice touch and one that our similar but simpler WSPR beacon lacked.

This beacon had us beat on performance, too. [IgrikXD] managed to hit Texas and Colorado from the edge of the North Sea on several bands, which isn’t too shabby at all with a fraction of a watt.

Thanks to [STR-Alorman] for the tip.

[via r/amateurradio]

Life Imitates ART (ART-13, That Is)

November 23, 2023 by 4 Comments

[Mr. Carlson] has been restoring vintage military radios, and as part of his quest, he received an ART-13 transmitter. Before he opened the shipping box, he turned on the camera, and we get to watch from the very start in the video below. These transmitters were originally made by Collins for the Navy with an Army Air Corps variant made by Stewart-Warner. Even the Russians made a copy, presumably by studying salvaged units from crashed B-29s.

The transmitter puts out 100 watts at frequencies up to 18.1 MHz. The tubes needed a plate supply, and so, like many radios of the era, this one used a dynamotor. Think of it as a motor running at one voltage and turning a generator that produces a (usually) higher voltage. If you ever used a radio with one, you know you didn’t need an “on the air” sign — the whine of the thing spinning would let everyone know you had the key or microphone button pushed down. It’s an interesting piece of bygone tech that we’ve looked into previously.

The transmitter wasn’t in perfect shape, but we’ve seen worse. When the lid comes off, you can practically smell the old radio odor. There are tubes, coils, and even a vacuum relay, presumably for transmit/receive switching of the antenna. [Carlson] also tears open the dynamotor which is something you don’t see every day.

Continue reading “Life Imitates ART (ART-13, That Is)” →

Hackaday Links Column Banner

Hackaday Links: August 27, 2023

August 27, 2023 by 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.

Continue reading “Hackaday Links: August 27, 2023” →

Radio Apocalypse: Hardening AM Radio Against Disasters

June 6, 2023 by 64 Comments

If you’ve been car shopping lately, or even if you’ve just been paying attention to the news, you’ll probably be at least somewhat familiar with the kerfuffle over AM radio. The idea is that in these days of podcasts and streaming music, plain-old amplitude modulated radio is becoming increasingly irrelevant as a medium of mass communication, to the point that automakers are dropping support for it from their infotainment systems.

The threat of federal legislation seems to have tapped the brakes on the anti-AM bandwagon, at least for now. One can debate the pros and cons, but the most interesting tidbit to fall out of this whole thing is one of the strongest arguments for keeping the ability to receive AM in cars: emergency communications. It turns out that about 75 stations, most of them in the AM band, cover about 90% of the US population. This makes AM such a vital tool during times of emergency that the federal government has embarked on a serious program to ensure its survivability in the face of disaster.

Continue reading “Radio Apocalypse: Hardening AM Radio Against Disasters” →

Not A Pot, Not An Encoder: Exploring Synchros For Rotational Sensing

February 1, 2023 by 25 Comments

We’re all familiar with getting feedback from a rotating shaft, for which we usually employ a potentiometer or encoder. But there’s another device that, while less well-known, has some advantages that just might make it worth figuring out how to include it in hobbyist projects: the synchro.

If you’ve never heard of a synchro, don’t feel bad; as [Glen Akins] explains, it’s an expensive bit of kit most commonly found in avionics gear. It’s in effect a set of coaxial transformers with a three-phase stator coil and a single-phase rotor. When excited by an AC reference voltage, the voltage induced on the rotor coil is proportional to the cosine of the angle between the rotor and stator. It seems simple enough, but the reality is that synchros present some interfacing challenges.

[Glen] chose a surplus altitude alert indicator for his experiments, a formidable-looking piece of avionics. Also formidable was the bench full of electronics needed to drive and decode the synchro inside it — a 26-volt 400-Hz AC reference voltage generator, an industrial data acquisition module to digitize the synchro output, and an ESP32 dev board with a little OLED display to show the results. And those are impressive; as seen in the video below, the whole setup is capable of detecting tenth-of-a-degree differences in rotation.

The blog post has a wealth of detail on using synchros, as does this Retrotechtacular piece from our own [Al Williams]. Are they practical for general hobbyist use? Probably not, but it’s still cool to see them put to use.

Continue reading “Not A Pot, Not An Encoder: Exploring Synchros For Rotational Sensing” →