antenna

225 Articles

You Can’t Fix What You Can’t Measure

July 10, 2021 by 13 Comments

Last year, as my Corona Hobby™, I took up RC plane flying. I started out with discus-launched gliders, and honestly that’s still my main love, but there’s only so much room for hackery in planes that are designed to be absolutely minimum weight and maximum performance; these are the kind of planes that notice an extra half gram in the tail. So I’ve also built a few crude workhorse planes — the kind of things that you could slap a 60 g decade-old GoPro on and it won’t even really notice. Some have ended their lives in trees, but most have been disassembled and reincarnated — the electronics live on in the next body.

The journey has been really fun. I’ve learned about aerodynamics, gotten an excuse to put together a 4-axis hot-wire CNC styrofoam cutter, and covered everything in sight with carbon fiber tow, which is cheaper than you might think but makes the plane space-age. My current workhorse has bolted on an IMU, GPS, and a minimal Ardupilot setup, though I have yet to really put it through its paces. What’s holding me back is the video link — it just won’t work reliably further than a few hundred meters, and I certainly don’t trust it to get out of line-of-sight.

My suspicion is that the crappy antennas I have are holding me back, which of course is an encouragement to DIY, but measuring antennas in the 5.8 GHz band is tricky. I’d love to just be able to buy one of the cheap vector analyzers that we’ve covered in the past — anyone can make an antenna when they can see what they’re doing — but they top out at 2.4 GHz or lower. No dice. I’m blind in 5.8 GHz.

Of course, I do have one way in, and that’s tapping into the received signal strength indicator (RSSI) of a dedicated 5.8 GHz receiver, and just testing antennas out in practice, but that only gives a sort of loose better-worse indication. More capacitance or more inductance? Plates closer together or further apart? Try it out and see, I guess, but it’s time-consuming.

Moral of the story: don’t take measurement equipment for granted. Imagine trying to build an analog circuit without a voltmeter, or to debug something digital without a logic probe. Sometimes the most important tool is the one that lets you see the problem in the first place.

This article is part of the Hackaday.com newsletter, delivered every seven days for each of the last 200+ weeks. It also includes our favorite articles from the last seven days that you can see on the web version of the newsletter. Want this type of article to hit your inbox every Friday morning? You should sign up!

Balloon Antenna Doesn’t Need A Tower

June 11, 2021 by 20 Comments

What do you do with floral wire and balloons from Dollar Tree? If you are [Ham Radio Crash Course], you make a ham radio antenna. Floral wire is conductive, and using one piece as a literal sky hook and the other as a ground wire, it should do something. He did use, as you might expect, a tuner to match the random wire length.

The first attempt had too few balloons and too much wind. He eventually switched to a non-dollar store helium tank. That balloon inflates to about 36 inches and appears to have plenty of lift. It looks like by the end he was using two of them.

Continue reading “Balloon Antenna Doesn’t Need A Tower” →

Send Old-Fashioned Pager Messages With New-Fashioned Hardware

May 18, 2021 by 5 Comments

In a world of always-connected devices and 24/7 access to email and various social media and messaging platforms, it’s sometimes a good idea to take a step away from the hustle and bustle for peace of mind. But not too big of a step. After all, we sometimes need some limited contact with other humans, so that’s what [EverestX] set out to do with his modern, pocket-sized communication device based on pager technology from days of yore.

The device uses the POCSAG communications protocol, a current standard for pager communications that allows for an SMS-like experience for those still who still need (or want) to use pagers. [EverestX] was able to adapt some preexisting code and port it to an Atmel 32u4 microcontroller. With a custom PCB, small battery, an antenna, and some incredibly refined soldering skills, he was able to put together this build with an incredibly small footprint, slightly larger than a bottle cap.

Once added to a custom case, [EverestX] has an excellent platform for sending pager messages to all of his friends and can avoid any dreaded voice conversations. Pager hacks have been a favorite around these parts for years, and are still a viable option for modern communications needs despite also being a nostalgic relic of decades past. As an added bonus, the 32u4 microcontroller has some interesting non-pager features that you might want to check out as well.

Thanks to [ch0l0man] for the tip!

Monitor SpaceX Rocket Launches With Software-Defined Radio

March 11, 2021 by 15 Comments

The amateur radio community has exploded with activity lately especially in the software-defined radio (SDR) area since it was found that a small inexpensive TV tuner could be wrangled to do what only expensive equipment was able to do before. One common build with these cards is monitoring air traffic, which send data about their flights out in packets over the radio and can easily be received and decoded now. It turns out another type of vehicle, SpaceX’s Falcon 9 spacecraft, reports data via radio as well and with some slightly upgraded hardware it’s possible to “listen in” to these flights in a similar way.

Reddit users [derekcz] and [Xerbot] used a HackRF module to listen in to the Falcon 9’s data transmissions during its latest launch. While the HackRF is a much more expensive piece of equipment compared to the RTL-SDR dongles used to listen in on aircraft, it is much more capable as well, with a range from 1 MHz to 6 GHz. Using this SDR peripheral as well as a 1.2 m repurposed satellite dish, the duo were able to intercept the radio transmissions from the in-flight rocket. From there, they were recorded with GNU Radio, converted into binary data, and then translated into text.

It seems as though the data feed included a number of different elements including time, location information, and other real-time data about the rocket’s flight. It’s a great build that demonstrates the wide appeal of software-defined radio, and if you want to get started it’s pretty easy to grab a much cheaper dongle and use it for all kinds of applications like this. Go check out [Tom Nardi]’s piece on the last seven years of RTL-SDR to get caught up to speed.

Thanks to [Adrian] for the tip!

Capstan Winch Central To This All-Band Adjustable Dipole Antenna

February 23, 2021 by 18 Comments

The perfect antenna is the holy grail of amateur radio. But antenna tuning is a game of inches, and since the optimum length of an antenna depends on the frequency it’s used on, the mere act of spinning the dial means that every antenna design is a compromise. Or perhaps not, if you build this infinitely adjustable capstan-winch dipole antenna.

Dipoles are generally built to resonate around the center frequency of one band, and with allocations ranging almost from “DC to daylight”, hams often end up with a forest of dipoles. [AD0MZ]’s adjustable dipole solves that problem, making the antenna usable from the 80-meter band down to 10 meters. To accomplish this feat it uses something familiar to any sailor: a capstan winch.

The feedpoint of the antenna contains a pair of 3D-printed drums, each wound with a loop of tinned 18-gauge antenna wire attached to some Dacron cord. These make up the adjustable-length elements of the antenna, which are strung through pulleys suspended in trees about 40 meters apart. Inside the feedpoint enclosure are brushes from an electric drill to connect the elements to a 1:1 balun and a stepper motor to run the winch. As the wire pays out of one spool, the Dacron cord is taken up by the other; the same thing happens on the other side of the antenna, resulting in a balanced configuration.

We think this is a really clever design that should make many a ham happy across the bands. We even see how this could be adapted to other antenna configurations, like the end-fed halfwave we recently featured in our “$50 Ham” series.

3D Print Your Next Antenna

February 19, 2021 by 40 Comments

Building antennas is a time-honored ham radio tradition. Shortwave antennas tend to be bulky but at VHF frequencies the antenna sizes are pretty manageable. [Fjkaan’s] 2 meter quadrifilar helicoidal antenna is a good example and the structure for it can be created with 3D printing combined with electrical conduit.

Many people, including [G4ILO] use PVC pipe for the structure, and that design inspired [Fjkaan]. Despite being a bit less substantial, the conduit seems to work well and it is easy to cut. The helical design is common for satellite work owing to its circular polarization and omnidirectional pattern.

Continue reading “3D Print Your Next Antenna” →

3D Printer Makes Ham Antenna Portable

February 9, 2021 by 8 Comments

You don’t normally think of a 3D printer as a necessity for an antenna project. However, if you are interested in making a handy portable antenna, you might want to melt some plastic. [N2MXX] has an end fed antenna winder design that also contains the necessary matching toroid. This would be just the thing to throw in your backpack for portable operation.

The end-fed configuration is handy for portability too, because you can easily secure one end and feed the other end. Compare that to a dipole where you have to feed a high point and secure both ends.

Continue reading “3D Printer Makes Ham Antenna Portable” →