ESP32 WiFi Hits 10km with a Little Help

[Jeija] was playing with some ESP32s and in true hacker fashion, he wondered how far he could pull them apart and still get data flowing. His video answer to that question covers the Friis equation and has a lot of good examples of using the equation, decibels, and even a practical example that covers about 10km. You can see the video below.

Of course, to get that kind of range you need a directional antenna. To avoid violating regulations that control transmit power, he’s using the antenna on the receiving end. That also means he had to hack the ESP32 WiFi stack to make the device listen only on one side. The hack involves putting the device in promiscuous mode and only monitoring the signals being sent. You can find the code involved on GitHub (complete with a rickrolling application).

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RadiantBee Is A Flying Microwave Antenna Calibration System

Many of the projects we link to here at Hackaday have extensive write-ups, pages of all the detail you could need. Sometimes though we happen upon a project with only a terse description to go on, but whose tech makes it one worth stopping for and unpicking the web of information around it.

Such a project is [F4GKR] and [F5OEO]’s RadiantBee, an attempt to use a beacon transmitter on a multirotor as an antenna calibration platform. (For more pictures, see this Twitter feed.) In this case a multirotor has a GPS and a 10 GHz beacon that emits 250 ms chirps, from which the receiver can calculate signal-to-noise ratio as well as mapping the spatial response of the antenna.

The transmitter uses a Raspberry Pi feeding a HackRF SDR and a 10 GHz upconverter, while the receiver uses an RTL-SDR fed by a 10 GHz to 144 MHz downconverter. The antennas they are testing are straightforward waveguide horns, but the same principles could be applied to almost any antenna.

There was a time when antenna design at the radio amateur level necessitated extensive field testing, physical measurements with a field strength meter over a wide area, correlation of figures and calculation of performance. But with computer simulation the field has become one much more set in the lab, so it’s rather refreshing to see someone producing a real-world simulation rig. If you ever get the chance to evaluate an antenna through real-world measurement, grasp it with both hands. You’ll learn a lot.

We’ve covered very few real-world antenna tests, but there is mention in this write-up of a radar antenna test of a measurement session on a football field.

Via Southgate ARC.

Adding an External Antenna to the Raspberry Pi Zero W

Putting a complete WiFi subsystems on a single-board computer is no mean feat, and on as compact a board as the Zero W, it’s quite an achievement. The antenna is the tricky part, since there’s only so much you can do with copper traces.

The new Raspberry Pi Zero W’s antenna is pretty innovative, but sometimes you need an external antenna to reach out and touch someone. Luckily, adding an external antenna to the Zero W isn’t that tough at all, as [Brian Dorey] shows us. The Pi Zero W’s designers thoughtfully included solder pads for an ultra-miniature surface-mount UHF jack. The jack pads are placed very close to the long, curving trace that acts as a feedline to the onboard antenna. There’s even a zero ohm SMT resistor that could be repositioned slightly to feed RF to the UHF jack. A little work with a soldering iron and [Brian]’s Pi was connected to an external antenna.

[Brian] includes test data, but aside from a few outliers, the external antenna doesn’t seem to offer a huge advantage, at least under his test conditions. This speaks to the innovative design of the antenna, which [Roger Thornton] from the Raspberry Pi Foundation discussed during last week’s last week’s Hack Chat. Check out the archive for that and more.

Thanks to [theEngineer] for the tip.

Antenna Analyzer is a Lab in a Box

There was a time when the measure of a transmitting radio antenna was having it light an incandescent bulb. A step up was a classic SWR/Power meter that showed you forward and reflected power. Over the years, a few other instruments have tried to provide a deeper look into antenna performance. However, the modern champion is the antenna analyzer which is a way of measuring vector impedance.

[Captain Science] did a review of an inexpensive N1201SA analyzer. This device is well under $200 from the usual Chinese sellers. The only thing a bit odd is the frequency range which is 140 MHz to 2700 MHz. For some extra money (about $80 or $100 more) you can drop the low-end frequency to just under 35 MHz.

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Loop Antenna is Portable

We don’t know if [OH8STN] has a military background, but we suspect he might since his recent post is about a “DIY Man Portable Magnetic Loop Antenna.” “Man-portable” is usually a military designation, and — we presume — he wouldn’t object to a woman transporting it either.

[OH8STN] started with a Chameleon antenna starter kit. This costs about $100 and is primarily a suitable variable capacitor with a 6:1 reduction drive premounted and soldered. Of course, you could source your own, but finding variable capacitors that can handle transmit duty (admittedly, these can apparently handle about 10 W continuous or 25 W on single sideband) can be tricky, especially these days. Although he started with a kit, he did modify the antenna to switch between two different sets of ham radio bands. You can see the antenna in the video below.

Loop antennas aren’t ideal–but neither is any other small antenna. Because the loop is tightly tuned to a particular frequency, it requires retuning for even relatively small frequency changes, even though it can operate on many different frequencies. If you want more technical details, you might enjoy this recent presentation from [W4RAX]. The links at the end are worth checking out, too.

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A Lightweight Two Metre Carbon Fibre Yagi Antenna

If you’ve ever cast your eye towards the rooftops, you’ll be familiar with the Yagi antenna. A dipole radiator with a reflector and a series of passive director elements in front of it, you’ll find them in all fields of radio including in a lot of cases the TV antenna on your rooftop.

In the world of amateur radio they are used extensively, both in fixed and portable situations. One of their most portable uses comes from the amateur satellite community, who at the most basic level use handheld Yagi antennas to manually track passing satellites. As you can imagine, holding up an antenna for the pass of a satellite can be a test for your muscles, so a lot of effort has gone into making Yagis for this application that are as lightweight as possible.

[Tysonpower] has a contribution to the world of lightweight Yagis, he’s taken a conventional design with a PVC boom and updated it with a stronger and lighter boom made from carbon fibre composite pipe. The elements are copper-coated steel welding rods, some inexpensive aluminium clamps came from AliExpress, and all is held together by some 3D-printed parts. As a result the whole unit comes in at a claimed bargain price of under 20 Euros.

This antenna is for the 2 M (144 MHz) amateur band, but since it’s based on the [WB0CMT] “7 dB for 7 bucks”  (PDF) design it should be easily modified for other frequencies. The 3D printed parts can be found on Thingiverse,  and he’s also posted a couple of videos in German. We’ve posted the one showing the build below the break, you can find the other showing the antenna being tested at the link above.

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Hackaday Links: February 5, 2017

A lot of people around here got their start in electronics with guitar pedals. This means soldering crappy old transistors to crappy old diodes and fawning over your tonez, d00d.  Prototyping guitar pedals isn’t easy, though, and now there’s a CrowdSupply project to make it easier The FX Development Board is just that — a few 1/4″ jacks, knobs, pots, power supply, and a gigantic footswitch to make prototyping guitar pedals and other musical paraphernalia easy. Think of it as a much more feature-packed Beavis Board that’s still significantly cheaper.

How do Communicators in Star Trek work? Nobody knows. Why don’t the crew always have to tap their badge before using it? Nobody knows. How can the com badge hear, ‘Geordi to Worf’, and have Worf instantly respond? Oh, we’ve argued about this on IRC for years now. Over on Hackaday.io, [Joe] is building a Star Trek com badge. The electronics are certainly possible with modern microcontrollers, but for the enclosure, we’ll have to review a few scenes from Time’s Arrow and The Enemy.

[Alois] was working with an Intel Edison on a breadboard. He was generating a signal, and sending it through a little tiny breadboard wire to an oscilloscope. The expected waveform should have been a nice square wave at 440MHz. What he got out of this wire was a mess. You shouldn’t use long wires when probing circuits. That little breadboard wire was a perfect radiator for 440MHz, and the entire setup turned into an antenna.

[Douglas] is running a Kenwood TM-D710A as his amateur radio rig. This radio does APRS stuff, but it requires an external GPS and power source to do it right. GPS receivers are now very small and very cheap, so [Douglas] just stuffed a GPS module inside his radio. The module itself is a GP-20U7, a tiny GPS module the size of a postage stamp, and wired it up to a few pads on the radio PCB.

Here’s an upcoming Kickstarter that’s going straight to the front page of Boing Boing. It’s Pong, in coffee table format which we first saw last Spring. Instead of racing the beam, this version of Pong is mechanical. The ball is a cube, the paddles are slightly longer cubes, and the entire game is a highly refined CNC machine. Here’s something from seven years ago that’s also Pong in coffee table format. Pongmechanik is electromechanical Pong, built entirely out of switches, relays, and a few motors.