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Fishing for Radio Signals With the Moxon Antenna

mox-antenna

[Bill Meara] has finished his latest project, a Moxon antenna for HF on 17 meters. [Bill] is well-known here on Hackaday. When not building awesome radios, he can be found ranting about ham radio. His new antenna turned out to be a true hack. He even used a hacksaw to build it!

The Moxon antenna is named for the late [Les Moxon, G6XN] who first described it in “Two-Element Driven Arrays”, a QST magazine article published in July of 1952.  [Bill] built his Moxon loosely based on [Jim/AE6AC's] excellent instructions. The design is incredibly simple – a two element directional antenna using crappie fishing poles as spreaders. That’s crappie as in the fish, not the quality of the pole. Crappie poles are typically made up of telescoping sections of graphite or fiberglass  in common lengths of 14, 16, and 20 feet. The poles can be bought for under $20 at sporting goods stores. [Bill] used 16 foot poles purchased from Amazon.

The antenna is created by connecting all four poles at their bases in an X shape. The wire elements are stretched across the ends of the poles. The entire antenna bends up as the stiff poles hold the driven and reflector elements in tension. [Bill] used some scrap wood and U-bolts to attach the fishing poles, and bungee cord ends at the tips. Since the antenna is directional, [Bill] added a TV antenna rotor to spin the beam around. The antenna is so light that one could get by with a couple of cords and the “Armstrong method” of antenna rotation.

Once up on the roof, [Bill] found his antenna really performed. He was easily able to cross the Atlantic from his Northern Virginia home to France, Belgium, and Latvia. The mostly horizontal antenna makes it a bit more unobtrusive than other directional designs. [Bill] mentions that his neighbors haven’t revolted yet, so he’s continuing to enjoy the fruits of his antenna labors.

Dodgy Hotel, Beer and A WWII Era Tube Receiver

bc-22e ww2 reciever operating in a hotel

In the luxurious accommodations provided by Motel 8 and armed only with a few tools and a six pack – a pair of amateur radio enthusiasts attempted the repair of an old WWII era BC-224E receiver. They picked up the boat anchor antique receiver, which was in unknown condition, from a flea market while in town for the Dayton Hamvention, brought it back to their hotel and got to work.

The BC-224E came in two parts – the receiver and the power supply. The speaker for the system, which is actually located in the power supply, is driven by a large inductor.  Apparently when the receiver was constructed, the permanent magnets of the day were not powerful enough to drive a speaker.

Fortunately, the receiver also came with some schematics, allowing [Gregory] and his fellow radio enthusiast to reverse engineer the power supply. After a few tweaks and cap swaps, they crossed their fingers and plugged it in. Stay tuned to see what happened next.

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Oinker is Twitter for HAMs

oinker

Have you ever wanted to send a quick message to your HAM radio buddies over the air but then realized you forgot your radio at home? [Troy] created Oinker to remedy this problem. Oinker is a Perl script that turns emails into audio.

The script monitors an email account for new messages and then uses the Festival text-to-speech engine to transform the text into audio. [Troy] runs Oinker on a Raspberry Pi, with the Pi’s audio output plugged directly into an inexpensive ham radio. The radio is then manually tuned to the desired transmit frequency. Whenever Oinker see’s a new email, that message is converted into speech and then output to the transmitter.

The script automatically appends your HAM radio call sign to the end of every message to ensure you stay within FCC regulations. Now whenever [Troy] runs into some bad traffic on the road, he can send a quick SMS to his email address and warn his HAM radio buddies to stay clear of the area.

Listening To A Swarm Of Satellites In Orbit

kicksat

A few months ago, we heard of a Kickstarter with an amazing goal: give everyone with $300 burning a hole in their pocket their very own satellite orbiting Earth. Time passes, the mothership has been launched, and in just a few short hours, over a hundred of these personal femtosatellites will be released into low Earth orbit.

The Kicksat consists of a 3U cubesat that was recently launched aboard the SpaceX CRS-3 mission to the International Space Station. Inside this cubesat are over one hundred satellites called Sprites, loaded up with solar cells, magnetometers, a microcontroller and a radio to communicate with ground stations below. The current mission is a proof of concept, but if everything goes as planned, similar satellites can be deployed into the path of incoming asteroids, or whenever a mission calls for a swarm of small smart devices covering a huge area.

Already the Kicksat mothership has been tracked by a few enterprising amateur radio enthusiasts but the deployment of the Sprites isn’t scheduled until today at 4:00 PM EDT (20:00 GMT). After that, the Sprites will be on their own, spewing out data and the initials of kickstarter backers to most of the population of Earth.

For anyone worrying about these Sprites causing an ablation cascade or a Kessler syndrome, don’t. Orbital decay is a function of surface area and mass, and these extremely lightweight thin rectangles will burn up in the atmosphere in a few week’s time. The lack of radiation hardening on the Sprites won’t be a problem, either. This shouldn’t be a surprise, as they’re orbiting well within our wonderful, protective magnetosphere, and there are digital cameras, tablets, and other much more radiation sensitive electronics that have been working perfectly on the ISS for years now.

You can check out the current location of the orbiting Kicksat mothership on the project website, read the updates on the project blog, or check out our coverage of the Kicksat program from last year’s world maker faire in New York. Relevant videos below.

Oh, and if you have a USB TV tuner, a good antenna, LNA, and some experience with SDR, here’s what you need to listen in.

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Pi-Powered Radio Over IP

Pi

[KP4TR] connected a Raspberry Pi to a small, cheap handheld radio, allowing anyone within a few miles of his house to connect to amateur radio operators all around the world.

For the hardware, [KP4TR] is using a Raspi, a Baofeng BF-888s 400MHz – 470MHz walkie-talkie radio, a USB sound card, and a pair of transformers for the 5V and 3.7V lines. All this is tucked away in a remakably vintage-looking plate and standoff enclosure, complete with acorn nuts and an RGB LED connected to the Raspi’s GPIO to indicate whether the radio is transmitting or receiving.

The software used is SVXLink, a Linux port of the Echolink software. This app allows hams the world over to connect to very distant radios over the Internet.

You can check out the video demos of the system below.

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SSTV beacon based on a Raspberry Pi

The Budapest hackerspace did some joint work with a local ham radio club and created an SSTV beacon housed inside a CCTV case that takes an image of its environment and transmits it using slow-scan television over ham bands.

As the title says, the build uses a Raspberry Pi to process the image taken from its camera and then transmits it over the air using a Ricofunk UHF transceiver with a main frequency of 433.425MHz. On the software side, PySSTV is used to convert images to frequency/time tuples, UNIXSSTV then creates the actual audio file and finally sox plays it. To avoid screwing up the Raspberry SD card, every part of the filsystem is either mounted in read-only mode (things like /home and /usr) or uses a ramdisk (things like /tmp and logs).

The plans, schematics and source code are available, so they hope that other hackerspaces will join the ranks!

Retrotechtacular: Fundamentals of AM and FM Radio Communication

AM Transmitter

How radios send and receive information can seem magical to the uninformed. For some people, this week’s Retrotechtacular video, “Frequency Modulation – Part 1 Basic Principles”, from the US Army Department of Defense 1964 will be a great refresher, and for others it will be their first introduction into the wonderful world of radio communications.

The stated objective is to teach why FM radio communication reduces interference which normally afflicts AM radio communications. Fundamentals of AM and FM is a better description, however, because the first part of the video nicely teaches the principles of AM and FM radio communications. It isn’t until later in the clip that it delves into interference, advantages of FM modulation, and detailed functioning of FM radio. The delivery is slow at times and admittedly long, yet the pace is perfect for a young ham to follow along with plenty of time to soak in the knowledge. If you’re still on the fence about becoming a ham here’s some words or encouragement.

Though the video isn’t aimed at ham radio users it does address core knowledge needed by amateur radio hobbyists. Amateur radio is full of many exciting communication technologies and you should have a clear understanding of AM and FM communication methodologies before getting on Grandpa’s information super highway. Once you have your ham license (aka ticket) you have privileges to create and test amazing ham related hacks, like [Lior] implementing full programmable control of a Baofeng UV5R ham radio using an Arduino.

Join us after the break to watch the video.

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