Radio Hacks

1350 Articles

Antenna Measurement In Theory And Practice

December 6, 2024 by 9 Comments

If you want to analyze an antenna, you can use simulation software or you can build an antenna and make measurements. [All Electroncs Channel] does both and show you how you can do it, too, in the video below.

The antenna in question is a loop antenna. He uses a professional VNA (Vector Network Analyzer) but you could get away with a hobby-grade VNA, too. The software for simulation is 4NEC2.

The VNA shows the electrical characteristics of the antenna, which is one of the things you can pull from the simulation software. You can also get a lot of other information. You’d need to use a field strength meter or something similar to get some of the other information in the real world.

The antenna simulation software is a powerful engine and 4NEC2 gives you an easy way to use it with a GUI. You can see all the graphs and plots easily, too. Unfortunately, it is Windows software, but we hear it will run under Wine.

The practical measurement is a little different from the simulation, often because the simulation is perfect and the real antenna has non-ideal elements. [Grégory] points out that changing simulation parameters is a great way to develop intuition about — in this case — antennas.

Want to dive into antennas? We can help with that. Or, you can start with a simple explanation.

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LongChat For Ham Radio

December 4, 2024 by 38 Comments

There was a time when ham radio operators were known for having long conversations over the radio — rag chewing, as they called it. A new program, LongChat, is a new entry into the ham radio software world that could bring chatting back to ham radio. [Tech Minds] has a video covering it (and using it), which you can see below.

While some people do talk using microphones or Morse code keys, there are a lot of digital modes now. Some, like RTTY or PSK31, can support conversations, but the more popular ones, like FT-8, are very stripped down. Your computer exchanges basic information with the other station’s computer, and that’s it.

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Car Radio Chip Goes Into DIY Build

December 3, 2024 by 15 Comments

[Sjef Verhoeven] still loves radio and enjoys the challenge of listening to radio signals from far away. He wanted to build his own radio and turned to the TEF6686 chip, a device often found in car radios. It is known to be very sensitive and seemed perfect for pulling in weak signals. So [Sjef] built this DIY radio and shares the details in this recent Spectrum post.

Unlike older radio-on-chip devices, the TEF6686 is a DSP, which, according to the post, is part of the reason it is ultrasensitive. Even though it is made for car radios, the device is versatile and can pick up shortwave as well as the usual broadcast bands, with the right configuration.

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Pushing 802.11ah To The Extreme With Drones

December 1, 2024 by 20 Comments

It might come as a surprise to some that IEEE, the Institute for Electrical and Electronics Engineers, does more than send out mailers asking people to renew their memberships. In fact, they also maintain various electrical standards across a wide range of disciplines, but perhaps the one most of us interact with the most is the 802.11 standard which outlines WiFi. There have been many revisions over the years to improve throughput but the 802.11ah standard actually looks at decreasing throughput in favor of extremely increased range. Just how far you can communicate using this standard seems to depend on how many drones you have.

802.11ah, otherwise known as Wi-Fi HaLow, operates in the sub-gigahertz range which is part of why it has the capability of operating over longer distances. But [Aaron] is extending that distance even further by adding a pair of T-Halow devices, one in client mode and the other in AP (access point) mode, on a drone. The signal then hops from one laptop to a drone, then out to another drone with a similar setup, and then finally down to a second laptop. In theory this “Dragon Bridge” could allow devices to communicate as far as the drone bridge will allow, and indeed [Aaron] has plans for future revisions to include more powerful hardware which will allow even greater distances to be reached.

While there were a few bugs to work out initially, eventually he was able to get almost two kilometers of distance across six devices and two drones. Something like this might be useful for a distributed network of IoT devices that are just outside the range of a normal access point. The Dragon Bridge borrowed its name from DragonOS, a Linux distribution built by [Aaron] with a wide assortment of software-defined radio tools available out of the box. He’s even put in on the Steam Deck to test out long-distance WiFi.

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Recreating Unobtainium Weather Station Sensors

November 26, 2024 by 19 Comments

Imagine you own a weather station. Then imagine that after some years have passed, you’ve had to replace one of the sensors multiple times. Your new problem is that the sensor is no longer available. What does a hacker like [Luca] do? Build a custom solution, of course!

[Luca]’s work concerns the La Crosse WS-9257F-IT weather station, and the repeat failures of the TX44DTH-IT external sensor. Thankfully, [Luca] found that the weather station’s communication protocol had been thoroughly reverse-engineered by [Fred], among others. He then set about creating a bridge to take humidity and temperature data from Zigbee sensors hooked up to his Home Assistant hub, and send it to the La Crosse weather station. This was achieved with the aid of a SX1276 LoRa module on a TTGO LoRa board. Details are on GitHub for the curious.

Luca didn’t just work on the Home Assistant integration, though. A standalone sensor was also developed, based on the Xiao SAMD21 microcontroller board and a BME280 temperature, pressure, and humidity sensor. It too can integrate with the Lacrosse weather station, and proved useful for one of [Luca’s] friends who was in the same boat.

Ultimately, it sucks when a manufacturer no longer supports hardware that you love and use every day. However, the hacking community has a way of working around such trifling limitations. It’s something to be proud of—as the corporate world leaves hardware behind, the hackers pick up the slack!

$40 Ham Antenna Works Six Bands

November 23, 2024 by 14 Comments

[My Ham Radio Journey] wanted to see if a “common person” (in his words) could build an effective vertical ham radio antenna. If you look at the video below, the answer is apparently yes.

He started with a 24-foot fishing rod and a roll of 22 gauge wire. The height of the antenna wire is just over 20 feet long and he has several ground radials, as you might expect for a vertical antenna.

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RFID From First Principles And Saving A Cat

November 23, 2024 by 5 Comments

[Dale Cook] has cats, and as he readily admits, cats are jerks. We’d use stronger language than that, but either way it became a significant impediment to making progress with an RFID-based sensor to allow his cats access to their litterbox. Luckily, though, he was able to salvage the project enough to give a great talk on RFID from first principles and learn about a potentially tragic mistake.

If you don’t have 20 minutes to spare for the video below, the quick summary is that [Dale]’s cats are each chipped with an RFID tag using the FDX-B protocol. He figured he’d be able to build a scanner to open the door to their playpen litterbox, but alas, the read range on the chip and the aforementioned attitude problems foiled that plan. He kept plugging away, though, to better understand RFID and the electronics that make it work.

To that end, [Dale] rolled his own RFID reader pretty much from scratch. He used an Arduino to generate the 134.2-kHz clock signal for the FDX-B chips and to parse the returned data. In between, he built a push-pull driver for the antenna coil and an envelope detector to pull the modulated data off the carrier. He also added a low-pass filter and a comparator to clean up the signal into a nice square wave, which was fed into the Arduino to parse the Differential Manchester-encoded data.

Although he was able to read his cats’ chips with this setup, [Dale] admits it was a long road compared to just buying a Flipper Zero or visiting the vet. But it provided him a look under the covers of RFID, which is worth a lot all by itself. But more importantly, he also discovered that one cat had a chip that returned a code different than what was recorded in the national database. That could have resulted in heartache, and avoiding that is certainly worth the effort too.

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