Hacklet 19 – Ham Radio

October 17, 2014 by Adam Fabio 20 Comments

Amateur, or ham radio operators have always been hackers. For much of the early 1900’s, buying a radio was expensive or impossible. Hams would build their own rigs, learning electronics and radio theory along the way. Time moves on, but hams keep hacking. Today we’re highlighting some of the best ham radio projects on Hackaday.io!

We start with [DainBramage1991] and his very practical RTL-SDR With Upconverter and Case. [DainBramage1991] fell in love with his low-cost RTL software defined radio dongle. He even added a Ham-It-Up upconverter to cover HF bands. The only problem was RF noise. the Realtek USB sticks tend to have little or no filtering, which means they are very susceptible to noise. [DainBramage1991] used the time-honored technique of insulating with copper clad board. Bits of PCB hold the RTL-SDR and upconverter in place. More PCB separates the two boards. Everything goes into a steel enclosure which keeps that unwanted RF at bay.

Next up is [Ryan Miller’s aka KG7HZQ]’s ham radio fox hunt attenuator. Ham radio fox hunt’s don’t involve baying dogs or horses. In this case a fox hunt is a contest to find hidden low power transmitters. If you’ve never tried one, it’s a heck of a lot of fun. One of the challenges with a fox hunt is to find the direction to the transmitter when you’re very close. Even with directional antennas, reflections and swamped receivers make it hard to figure out just where the transmitter is. The solution is an attenuator, which simply reduces the signal to a more reasonable value. [Ryan] also used copper clad PCB for his circuit. Since the attenuator parts are soldered directly to the PCB, this is more of a Manhattan style design. Two ceramic 1k pots help him achieve his goal of near perfect linear attenuation. We’re betting this attenuator will help [Ryan] win some contests!

Who says amateur radio won’t take you places? It may well be taking [Michael R Colton] to space! [Michael’s] project PortableSDR is one of the five finalists in The Hackaday Prize. We covered Michael earlier in the contest. PortableSDR started as a ham radio project: a radio system which would be easy for hams to take with them on backpacking trips. It’s grown into so much more now, with software defined radio reception and transmission, vector network analysis, antenna analysis, GPS, and a host of other features. We seriously love how [Michael] optimized a small LCD for waterfall display, tuning, and bandpass filter adjustment.

[W5VO] is working on an Ethernet to Radio Adapter. Every foot of coax in a radio system loses signal. Connections are even worse. It can all add up to several dB loss. [W5VO] wants to put an SDR at the antenna feed-point. With the signal path minimized, more watts make it out when transmitting, and more signal gets back to the receiver when listening. The interface between the SDR and host computer will be all digital; Ethernet to be precise. [W5VO] isn’t the first person to do something like this, microwave systems have had the transmitter and LNB at the antenna for years. That doesn’t take away from [W5VO’s] design at all He’s been quiet for a while, but we’re hoping he continues on his design!

Where is everyone else? We’re a bit light on projects this week, but we have a good reason. There just aren’t enough ham radio projects on Hackaday.io! We’re hoping to change that though. Are you an amateur radio enthusiast? Document your project on the site. Get input from other hams and push the envelope! You might even find yourself on the Ham Radio List!

That’s all for this episode of The Hacklet. As always, QRX is next week. Same hack time, same hack channel, bringing you the best of Hackaday.io! 73’s!

Digital “Crystal” Breathes New Life Into Old Radio

October 15, 2014 by Elliot Williams 11 Comments

[Bill Meara] of the Soldersmoke Podcast has a nice old Drake 2B radio, and wanted to use it for the 12 meter amateur band. These old radios normally make switching tuning bands easy — you just swap out one frequency crystal for another and you’re set.

Only [Bill] didn’t have the 21 MHz crystal that he needed. No problem, because he had a junk crystal, a hacksaw, and a modern direct-digital synthesis (DDS) chip sitting around. So he takes the donor crystal, cuts it open, and solders the two wires directly from the DDS to the crystal’s pins. Now he’s got a plug-in replacement digital oscillator that doesn’t require modifying the nice old Drake receiver at all. A sweet little trick.

The video’s a little bit long, but the money shot comes in around 5:00.

Now, one might worry about simply plugging a powered circuit (the DDS) in place of a passive element (the crystal), but it seems to work and the proof of the pudding is in the tasting. We wonder how far this digitally-controlled-analog-receiver idea could be extended.

A Mobile Radio Power Controller

October 10, 2014 by Brian Benchoff 24 Comments

[Pete], a.k.a. [KD8TBW] wanted to install his Yaesu radio in his car. From experience, he knew that having a radio in a car inevitable led to leaving it on once in a while, and this time, he wanted a device that would turn his rig on and off when the key was in the ignition. He ended up building a mobile radio power converter. It takes the 12V from the car when the alternator is running, and shuts everything off when the engine has stopped.

The Yaesu radio in question – an FT-8800 does have an automatic power off feature, but this is a terrible way of doing things. There is no way to turn the radio back on, and the radio must be left in a non-scanning mode.

In what he hopes to be his last design in EagleCAD, [Pete] whipped up a board featuring an ATtiny85 that measures the voltage in the car; when it’s ~14V, the alternator is working, and the radio can be switched on. When it drops to ~12V, it’s time to turn the radio off. It’s a great project, and with the 3D printed case, it can easily be shoved inside the console. Video below.

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THP Semifinalist: Cheap Satellite Transponder

September 20, 2014 by Brian Benchoff 7 Comments

In 2016, a communications satellite will be launched into geostationary orbit somewhere over the middle east. Normally, this is fairly ordinary occurrence. This satellite, however, will be carrying two amateur radio transponders for hams all across europe, africa, the middle east, and India. [2FTG] is building a satellite transponder to talk to this satellite, and he’s doing it with junk sitting around his workbench.

The uplink frequency for this satellite will be in the neighborhood of 2.4 GHz, and [2FTG] needed a way to deal with the out of band interference in this part of the spectrum. The easy and cheap way to do this is with filters made for the WiFi band. Instead, [2FTG] had a few cavity filters in his junk box and decided to go that route. It meant he had to retune the filters, a process that should be annoyingly hard. [2FTG] did it in thirty minutes.

Antennas are another matter, but since [2FTG] has a supply of metal coffee cans, this part of the build was just a matter of soldering a bit of wire to an SMA connector, drilling a hole (using a log as a drill stop, no less), and soldering the connector to the can.

The project featured in this post is a quarterfinalist in The Hackaday Prize.

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Fishing For Radio Signals With The Moxon Antenna

July 23, 2014 by Adam Fabio 4 Comments

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.

bc-22e ww2 reciever operating in a hotel

Dodgy Hotel, Beer And A WWII Era Tube Receiver

May 23, 2014 by Will Sweatman 21 Comments

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.

Continue reading “Dodgy Hotel, Beer And A WWII Era Tube Receiver” →

Oinker Is Twitter For HAMs

May 12, 2014 by Rick Osgood 57 Comments

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.