Custom LoRa Pager Designed With Care

March 24, 2019 by Lewin Day 13 Comments

LoRa is a useful technology if you need to send data a long way at low power levels. Leveraging this, [5Volt-Junkie] decided to build a small pager named the LoRaNicator.

Those who love a detailed build log will enjoy this. The pager features everything up to and including the kitchen sink. A Cortex M0+ runs the show, flashed with an Arduino compatible bootloader, while a RFM95W module handles the LoRa communications. There’s a pager vibrator and piezo buzzer for notifications, along with a LiPo charger to make keeping the battery topped up easy. There’s even an RTC and soft-power button module.

Even if the LoRa side of things isn’t relevant to your interests, it’s a great example of how to build a useful tool rather than just a proof-of-concept. Things like an easy-to-use interface and simple battery charging go a long way to making something usable in the field. [5Volt-Junkie] even goes so far as to point out that even solder mask matters – if you’re using an infrared oven, your black boards will need a different profile to the usual green PCBs.

All the hard work has paid off, creating an attractive end product that we’d be proud to pack with the rest of our ham gear. LoRa is a useful platform, and as we’ve seen, it can be useful for everything from viticulture to meterology. Video after the break.

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Making A 1940s Radio Digital With Nixies

March 17, 2019 by Brian Benchoff 10 Comments

Classix Philly One Oh Seven Nine is your home for Philly soul right at the top of the dial. That phrase, ‘top of the dial’ doesn’t mean much these days because we all have radios with a digital display and seek buttons. There was a time when radios actually had dials, but [glasslinger] is in a class all by himself. He’s adding a digital display to a 1940s radio, and he’s doing it with Nixie tubes.

The circuitry for the digital display for this AM radio requires getting the frequency the radio is tuned to. This is done by counting the oscillator frequency, then subtracting the IF. [glasslinger] is doing this with an Arduino (hey, it’s a legitimate engineering choice) and a 4040 12-bit binary counter as a pre-scaler. The Arduino does the math and then drives a few 74141 Nixie drivers, which then display the frequency of the receiver in beautiful glass tubes. Add in a single neon bulb for the thousands digit, and you have a four-digit display that will tell you the frequency you’re tuned to on an old AM radio.

The rest of the build consists of fixing up an old radio and gluing the veneer down again with modern glues that will last another seventy years. The finished cabinet was sanded, a bezel for the display was added, and since [glasslinger] has the equipment, he made a new, long neon tube to light up with the volume of the radio. And you thought a cat’s eye detector was cool.

This build is a tour de force, and something that is so incredibly modern but at the same time built on vintage technology. If you’ve got an hour and a half, we highly recommend checking out the build video below.

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Building A Magnetic Loop Antenna

March 17, 2019 by Lewin Day 21 Comments

Antennas come in many shapes and sizes, with a variety of characteristics making them more or less suitable for various applications. The average hacker with only a middling exposure to RF may be familiar with trace antennas, yagis and dipoles, but there’s a whole load more out there. [Eric Sorensen] is going down the path less travelled, undertaking the build of a self-tuning magnetic loop antenna.

[Eric]’s build is designed to operate at 100W on the 20 meter band, and this influences the specifications of the antenna. Particularly critical in the magnetic loop design is the voltage across the tuning capacitor; in this design, it comes out at approximately 4 kilovolts. This necessitates the careful choice of parts that can handle these voltages. In this case, a vacuum variable capacitor is used, rated to a peak current of 57 amps and a peak voltage of 5 kilovolts.

The magnetic loop design leads to antenna which is tuned to a very narrow frequency range, giving good selectivity. However, it also requires retuning quite often in order to stay on-band. [Eric] is implementing a self-tuning system to solve this, with a controller using a motor to actuate the tuning capacitor to maintain the antenna at its proper operating point.

If you’re unfamiliar with magnetic loop builds, [Eric]’s project serves as a great introduction to both the electrical and mechanical considerations inherent in such a design. We’ve seen even more obscure designs though – like these antennas applied with advanced spray techniques.

This SDR Uses A Tube

March 7, 2019 by Al Williams 17 Comments

When you think of a software defined radio (SDR) setup, maybe you imagine an IC or two, maybe feeding a computer. You probably don’t think of a vacuum tube. [Mirko Pavleski] built a one-tube shortwave SDR using some instructions from [Burkhard Kainka] which are in German, but Google Translate is good enough if you want to duplicate his feat. You can see a video of [Mirko’s] creation, below.

The build was an experiment to see if a tube receiver could be stable enough to receive digital shortwave radio broadcasts. To avoid AC line hum, the radio is battery operated and while the original uses an EL95 tube, [Mirko] used an EF80.

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Justin McAllister’s Simple, Post-Apocalypse-Friendly Antennas

March 4, 2019 by Donald Papp 10 Comments

Watch Justin McAllister’s presentation on simple antennas suitable for a zombie apocalypse and two things will happen: you’ll be reminded that everything antennas do is amazing, and their reputation for being a black magic art will fade dramatically. Justin really knows his stuff; there is no dangle-a-wire-and-hope-for-the-best in his examples. He demonstrates that it’s possible to communicate over remarkable distances with nothing more than an off-the-shelf radio, battery pack, and an antenna of simple design.

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The Cat, The Aircraft, And The Tiny Computer

March 4, 2019 by Jenny List 29 Comments

Sharing your life with a cat is a wonderful and fulfilling experience. Sharing your life with an awake, alert, and bored cat in the early hours when you are trying to sleep, is not. [Simon Aubury] has just this problem, as his cat [Snowy] is woken each morning by a jet passing over. In an attempt to identify the offending aircraft, he’s taken a Raspberry Pi and a software-defined radio, and attempted to isolate it by spotting its ADS-B beacon.

The SDR was the ubiquitous RTL chipset model, and it provided a continuous stream of aircraft data. To process this data he used an Apache Kafka stream processing server into which he also retrieved aircraft identifying data from an online service. Kafka’s SQL interface for interrogating multiple streams allowed him to untangle the mess of ADS-B returns and generate a meaningful feed of aircraft. This in turn was piped into an elasticsearch search engine database, upon which he built a Kibana visualisation.

The result was that any aircraft could be identified at a glance, and potential noise hotspots forecast. Whether all this heavy lifting was worth the end result is for you to decide, however it does provide an interesting introduction to the technologies and software involved. It is however possible to monitor ADS-B traffic considerably more simply.

Thanks [Oleg Anashkin] for the tip.

Be Vewy Vewy Quiet, We’re Hunting Baofengs

March 3, 2019 by Tom Nardi 24 Comments

In the world of ham radio, a “Fox Hunt” is a game where participants are tasked with finding a hidden transmitter through direction finding. Naturally, the game is more challenging when you’re on the hunt for something small and obscure, so the ideal candidate is a small automated beacon that can be tucked away someplace inconspicuous. Of course, cheap is also preferable so you don’t go broke trying to put a game together.

As you might expect, there’s no shortage of kits and turn-key transmitters that you can buy, but [WhiskeyTangoHotel] wanted to come up with something that could be put together cheaply and easily from hardware the average ham or hacker might already have laying around. The end result is a very capable “fox” that can be built in just a few minutes at a surprisingly low cost. He cautions that you’ll need a ham license to legally use this gadget, but we imagine most people familiar with this particular pastime will already have the necessary credentials.

The heart of this build is one of the fairly capable, but perhaps more importantly, incredibly cheap Baofeng handheld radios. These little gadgets are likely familiar to the average Hackaday reader, as we discussed their dubious legal status not so long ago. At the moment they are still readily available though, so if you need a second (or third…), you might want to pull the trigger sooner rather than later.

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