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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Does WiFi Kill Houseplants?

February 28, 2019 by Dan Maloney 72 Comments

Spoiler alert: No.

To come to that conclusion, which runs counter to the combined wisdom of several recent YouTube videos, [Andrew McNeil] ran a pretty neat little experiment. [Andrew] has a not inconsiderable amount of expertise in this area, as an RF engineer and prolific maker of many homebrew WiFi antennas, some of which we’ve featured on these pages before. His experiment centered on cress seeds sprouting in compost. Two identical containers were prepared, with one bathed from above in RF energy from three separate 2.4 GHz transmitters. Each transmitter was coupled to an amplifier and a PCB bi-quad antenna to radiate about 300 mW in slightly different parts of the WiFi spectrum. Both setups were placed in separate rooms in east-facing windows, and each was swapped between rooms every other day, to average out microenvironmental effects.

After only a few days, the cress sprouted in both pots and continued to grow. There was no apparent inhibition of the RF-blasted sprouts – in fact, they appeared a bit lusher than the pristine pot. [Andrew] points out that it’s not real science until it’s quantified, so his next step is to repeat the experiment and take careful biomass measurements. He’s also planning to ramp up the power on the next round as well.

We’d like to think this will put the “WiFi killed my houseplants” nonsense to rest – WiFi can even help keep your plants alive, after all. But somehow we doubt that the debate will die anytime soon.

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MIT IAP Tackles Radio

February 18, 2019 by Al Williams 2 Comments

MIT is well known for rigorous courses, but they also have a special four-week term at the start of each year called the IAP — Independent Activities Period. This year, the MIT Radio Society had several interesting presentations on both the history and application of radio. You weren’t there? No problem, as the nine lecture were all recorded for you to watch at your leisure. You can see one of the nine, below.

These aren’t some five minute quicky videos, either. They are basically live captures that run anywhere from an hour to almost two hours in length. The topics are a great mix including radio history, software-defined radio, propagation, radio astronomy, RADAR, and even 5G.

You might have to pick and choose. Some of the lectures are suitable for just about anyone. Some assume a bit more radio expertise in electronics or math. Still, they are all worth at least a cursory skim to see if you want to really sit and watch in detail. The only nitpick is that some presenters used a laser pointer that doesn’t show up on the inset slide graphics in the video. That makes sense because the inset slides are not really in the room, but it can make it a little difficult to understand what the speaker is pointing to on a crowded slide.

Of course, if you want to dive deep and you need more background, MIT — along with many other institutions — will let you use their learning material for free. We were especially fans of the circuits class but there are many others including just raw materials from OCW.

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Automated Radiosonde Tracking Via Open Source

February 10, 2019 by Lewin Day 3 Comments

Meteorological organisations across the world launch weather balloons on a regular basis as a part of their work in predicting whether or not it will rain on the weekend. Their payloads are called radiosondes, and these balloons deliver both telemetry and location data throughout their flightpath. Hobbyists around the globe have devoted time and effort to tracking and decoding these signals, and now it’s possible to do it all automatically, thanks to Radiosonde Auto RX.

The basis of the project is the RTL-SDR, everyone’s favourite low-cost software defined radio receiver. In this case, software is used to first hunt for potential radiosonde signals, before then decoding them and uploading the results to a variety of online services. Some of these are designed for simple tracking, while others are designed for live chase and recovery operations. Currently, the software only covers 3 varieties of radiosonde, but the team are eager to expand the project and have requested donations of other radiosondes for research purposes.

The team recently conducted a talk at linux.conf.au regarding the project, which goes into detail as to the decoding and tracking of the radiosonde data. If you’re eager to try it out, download the software, fetch your TV dongle and get cracking. You might also consider tracking cubesats while you’re at it. Video after the break.

via [crazyoperator], thanks to Slds Ernesto for the tip!

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