antenna

249 Articles

Building A Low-Cost Satellite Tracker

November 26, 2025 by 6 Comments

Looking up at the sky just after sunset or just before sunrise will reveal a fairly staggering amount of satellites orbiting overhead, from tiny cubesats to the International Space Station. Of course these satellites are always around, and even though you’ll need specific conditions to view them with the naked eye, with the right radio antenna and only a few dollars in electronics you can see exactly which ones are flying by at any time.

[Josh] aka [Ham Radio Crash Course] is demonstrating this build on his channel and showing every step needed to get something like this working. The first part is finding the correct LoRa module, which will be the bulk of the cost of this project. Unlike those used for most Meshtastic nodes, this one needs to be built for the 433 MHz band. The software running on this module is from TinyGS, which we have featured here before, and which allows a quick and easy setup to listen in to these types of satellites. This build goes much further into detail on building the antenna, though, and also covers some other ancillary tasks like mounting it somewhere outdoors.

With all of that out of the way, though, the setup is able to track hundreds of satellites on very little hardware, as well as display information about each of them. We’d always favor a build that lets us gather data like this directly over using something like a satellite tracking app, although those do have their place. And of course, with slightly more compute and a more directed antenna there is all kinds of other data beaming down that we can listen in on as well, although that’s not always the intent.

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Cheap VHF Antenna? Can Do!

November 18, 2025 by 6 Comments

The magnetic loop antenna is a familiar sight in radio amateur circles as a means to pack a high performance HF antenna into a small space. It takes the form of a large single-turn coil made into a tuned circuit with a variable capacitor, and it provides the benefits of good directionality and narrow bandwidth at the cost of some scary RF voltages and the need for constant retuning. As [VK3YE] shows us though, magnetic loops are not limited to HF — he’s made a compact VHF magnetic loop using a tin can.

It’s a pretty simple design; a section from the can it cut out and made into a C shape, with a small variable capacitor at the gap. The feed comes in at the bottom, with the feed point about 20 % of the way round the loop for matching. The bandwidth is about 100 MHz starting from the bottom of the FM broadcast band, and he shows us it receiving broadcast, Airband, and 2 meter signals. It can be used for transmitting too and we see it on 2 meter WSPR, but we would have to wonder whether the voltages induced by higher power levels might be a little much for that small capacitor.

He’s at pains to point out that there are many better VHF antennas as this one has no gain to speak of, but we can see a place for it. It’s tiny, if you’re prepared to fiddle with the tuning its high Q gets rid of interference, and its strong side null means it can also reduce unwanted signals on the same frequency. We rather like it, and we hope you will too after watching the video below.

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Optimizing VLF Antennas

September 4, 2025 by 12 Comments

Using digital techniques has caused a resurgence of interest in VLF — very low frequency — radio. Thanks to software-defined radio, you no longer need huge coils. However, you still need a suitable antenna. [Electronics Unmessed] has been experimenting and asks the question: What really matters when it comes to VLF loops? The answer he found is in the video below.

This isn’t the first video about the topic he’s made, but it covers new ground about what changes make the most impact on received signals. You can see via graphs how everything changes performance. There are several parameters varied, including different types of ferrite, various numbers of loops in the antenna, and wire diameter. Don’t miss the comment section, either, where some viewers have suggested other parameters that might warrant experimentation.

Don’t miss the 9-foot square antenna loop in the video. We’d like to see it suspended in the air. Probably not a good way to ingratiate yourself with your neighbors, though.

Between software-defined radio and robust computer simulation, there’s never been a better time to experiment with antennas and radios. We first saw these antennas in an earlier post. VLF sure is easier than it used to be.

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Neon Lamp Detects Lightning Strikes

July 19, 2025 by 16 Comments

For as mysterious, fascinating, and beautiful as lightning is at a distance, it’s not exactly a peaceful phenomenon up close. Not many things are built to withstand millions of volts and tens to hundreds of thousands of amps. Unsurprisingly, there’s a huge amount of effort put into lightning protection systems for equipment and resources that need to be outside where thunderstorms sometimes happen. Although most of us won’t be building personal substations, church steeples, or city-scale water towers in our backyards, we might have a few radio antennas up in the air, so it’s a good idea to have some lightning protection and possibly an alert system like [Joe] built.

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Field Testing An Antenna, Using A Field

May 21, 2025 by 9 Comments

The ARRL used to have a requirement that any antenna advertised in their publications had to have real-world measurements accompanying it, to back up any claims of extravagant performance. I’m told that nowadays they will accept computer simulations instead, but it remains true that knowing what your antenna does rather than just thinking you know what it does gives you an advantage. I was reminded of this by a recent write-up in which the performance of a mylar sheet as a ground plane was tested at full power with a field strength meter, because about a decade ago I set out to characterise an antenna using real-world measurements and readily available equipment. I was in a sense field testing it, so of course the first step of the process was to find a field. A real one, with cows. Continue reading “Field Testing An Antenna, Using A Field” →

Mylar Space Blankets As RF Reflectors

May 15, 2025 by 11 Comments

Metalized Mylar “space blankets” are sold as a survivalist’s accessory, primarily due to their propensity for reflecting heat. They’re pretty cheap, and [HamJazz] has performed some experiments on their RF properties. Do they reflect radio waves as well as they reflect heat? As it turns out, yes they do.

Any antenna system that’s more than a simple radiator relies on using conductive components as reflectors. These can either be antenna elements, or the surrounding ground acting as an approximation to a conductor. Radio amateurs will often use wires laid on the ground or buried within it to improve its RF conductivity, and it’s in this function that he’s using the Mylar sheet. Connection to the metalized layer is made with a magnet and some aluminium tape, and the sheet is strung up from a line at an angle. It’s a solution for higher frequencies only due to the restricted size of the thing, but it’s certainly interesting enough to merit further experimentation.

As you can see in the video below, his results are derived in a rough and ready manner with a field strength meter. But they certainly show a much stronger field on one side resulting from the Mylar, and also in an antenna that tunes well. We would be interested to conduct a received signal strength test over a much greater distance rather than a high-level field strength test so close to the antenna, but it’s interesting to have a use for a space blanket that’s more than just keeping the sun away from your tent at a hacker camp. Perhaps it could even form a parabolic antenna.

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Radio Repeaters In The Sky

April 30, 2025 by 10 Comments

One of the first things that an amateur radio operator is likely to do once receiving their license is grab a dual-band handheld and try to make contacts with a local repeater. After the initial contacts, though, many hams move on to more technically challenging aspects of the hobby. One of those being activating space-based repeaters instead of their terrestrial counterparts. [saveitforparts] takes a look at some more esoteric uses of these radio systems in his latest video.

There are plenty of satellite repeaters flying around the world that are actually legal for hams to use, with most being in low-Earth orbit and making quick passes at predictable times. But there are others, generally operated by the world’s militaries, that are in higher geostationary orbits which allows them to serve a specific area continually. With a specialized three-dimensional Yagi-Uda antenna on loan, [saveitforparts] listens in on some of these signals. Some of it is presumably encrypted military activity, but there’s also some pirate radio and state propaganda stations.

There are a few other types of radio repeaters operating out in space as well, and not all of them are in geostationary orbit. Turning the antenna to the north, [saveitforparts] finds a few Russian satellites in an orbit specifically designed to provide polar regions with a similar radio service. These sometimes will overlap with terrestrial radio like TV or air traffic control and happily repeat them at brief intervals.

[saveitforparts] has plenty of videos looking at other satellite communications, including grabbing images from Russian weather satellites, using leftover junk to grab weather data from geostationary orbit, and accessing the Internet via satellite with 80s-era technology.

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