Drink Lots Of Beer To Raise Your Monopole

When we published a piece about an ADS-B antenna using a Coke can as a groundplane, Hackaday reader [2ftg] got in contact with us about something with a bit more… stature.

A monopole groundplane antenna is a single vertical conductor mounted on an insulator and rising up above a conductive groundplane. In radio terms the groundplane is supposed to look as something of a mirror, to provide a reflection of what would come from the other half of a dipole were there to be two conductors. You can use anything conductive as your monopole, a piece of wire, (in radio amateur humour) a piece of wet string, or even beer cans. “Beer cans?” you ask incredulously, expecting this to be another joke. Yes, beer cans, and [2ftg] has been good enough to supply us with a few examples. The first is a 57-foot stack of them welded together in the 1950s for use on the 80 metre band ( we suspect steel cans may have been more common than aluminum back then), the second is a more modest erection for the 2 metre band, and the final one consists of photographs only of an HF version that looks a little wavy and whose cans are a little less beery.

The reporting in the 1950s piece is rather cheesy, but does give a reasonable description of it requiring welding rods as reinforcement. It also gives evidence of the antenna’s effectiveness, showing that it could work the world. Hardly surprising, given that a decent monopole is a decent monopole no matter how many pints of ale you have dispatched in its making.

The Coke can ADSB can be seen in all its glory here, and if all this amateur radio business sounds interesting, here’s an introduction.

Beer cans picture: Visitor7 [CC BY-SA 3.0].

A Watch Only A Ham Can Use

We’re not sure what to make of this one. With the variety of smartwatches and fitness trackers out there, we can’t be surprised by what sort of hardware ends up strapped to wrists these days. So a watch with an RPN calculator isn’t too much of a stretch. But adding a hex editor? And a disassembler? Oh, and while you’re at it, a transceiver for the 70cm ham band? Now that’s something you don’t see every day.

The mind boggles at not only the technical prowess needed to pull off what [Travis Goodspeed (KK4VCZ)] calls the GoodWatch, but at the thought process that led to all these features being packed into the case of a Casio calculator watch. But a lot of hacking is more about the “Why not?” than the “Why?”, and when you start looking at the feature set of the CC430F6137 microcontroller [Travis] chose, things start to make sense. The chip has a built-in RF subsystem, intended no doubt to enable wireless sensor designs. The GoodWatch20 puts the transceiver to work in the 430-MHz band, implementing a simple low-power (QRP) beacon. But the real story here is in the hacks [Travis] used to pull this off, like using flecks of Post-It notes to probe the LCD connections, and that he managed to stay within the confines of the original case.

There’s some real skill here, and it makes for an interesting read. And since the GoodWatch is powered by a coin cell, we think it’d be a great entry for our Coin Cell Challenge contest.

[via r/AmateurRadio]

Radio Amateuring Like It’s 1975

It was a tweet from an online friend in the world of amateur radio, featuring a transmitter design published in Sprat, the journal of the G-QRP club for British enthusiasts of low-power radio. The transmitter was very simple, but seriously flawed: keying the power supply line would cause it to exhibit key clicks and frequency instability. It would probably have been far better leaving the oscillator connected full-time and keying the supply to the amplifier, with of course a suitable key click filter.

[M0CVO]'s Tweet that started it all
[M0CVO]’s Tweet that started it all
We’ve all probably made projects that get the job done at the expense of a bit of performance and economy, and from one angle this circuit is a fantastic example of that art. But it’s not the shortcomings of direct PSU keying a small transmitter that has brought it here, but observation instead of what it represents. Perhaps my social group of radio amateurs differs from the masses, but among them the universal lament is that there is nothing new in a simple transistor transmitter that could just as well have been published in 1977 as 2017.

To explain why this represents a problem, it’s worth giving some background. Any radio amateur will tell you that amateur radio is a wonderful and diverse pastime, in fact a multitude of pastimes rolled into one. Working DX? Got you covered. Contesting? UR 599 OM QRZ? Digital modes pushing the envelope of atmospheric propagation? Satellites? SDRs? GHz radio engineering? All these and many more can be yours for a modest fee and an examination pass. There was a time when radio was electronics, to all intents and purposes, and radio amateurs were at the vanguard of technology. And though electronics has moved on from those days of purely analogue communications and now stretches far beyond anything you’d need a licence and a callsign to investigate for yourself, there are still plenty of places in which an amateur can place themselves at the cutting edge. Software defined radio, for instance, or digital data transmission modes. With an inexpensive single board computer and a few components it is now possible to create a software-defined digital radio station with an extremely low power output, that can be copied on the other side of the world. That’s progress, it’s not so long ago that you would have required a lot of dollars and a lot of watts to do that. Continue reading “Radio Amateuring Like It’s 1975”

Slinky Walks Down Stairs and Picks up 80m Band

Originally intended as a way to stabilize sensitive instruments on ships during World War II, the Slinky is quite simply a helical spring with an unusually good sales pitch. But as millions of children have found out since the 1940’s, once you roll your Slinky down the stairs a few times, you’ve basically hit the wall in terms of entertainment value. So what if we told you there was yet another use for this classic toy that was also fun for a girl and a boy?

As it turns out, a cheap expandable metal coil just so happens to make for a pretty good antenna if you hook it up right. [Blake Hughes] recently took on this project and provided some detailed pictures and information for anyone else looking to hook a couple of Slinkies to their radio. [Blake] reports excellent results when paired to his RTL-SDR setup, but of course this will work with whatever kind of gear you might be using at these frequencies.

Before anyone gets out the pitchforks, admittedly this isn’t exactly a new idea. There are a few other write-ups online about people using a Slinky as a cheap antenna, such as this detailed analysis from a few years ago by [Frank Dörenberg]. There’s even rumors that soldiers used a Slinky from back home as a makeshift antenna during the Vietnam War. So this is something of an old school ham trick revived for the new generation of SDR enthusiasts.

Anyway, the setup is pretty simple. You simply solder the RF jack of your choice to two stretched out Slinkies: one to the center of the jack and one to outside. Then run a rope through them and stretch them out in opposite directions. The rope is required because the Slinky isn’t going to be strong enough when expanded to keep from laying on the ground.

One thing to keep in mind with a Slinky antenna is that these things are not exactly rated for outside use. Without some kind of treatment (like a spray on acrylic lacquer) , they’ll quickly corrode and fail. Though a better idea might simply to be to think of this as a temporary antenna that you put away when you’re done with. Thanks to the fact that the Slinky doesn’t get deformed even when stretching it out to maximum length, that’s relatively easy to accomplish.

If you’re looking for a good RTL-SDR to go along with your new Slinky antenna, check out this roundup of some of the options that are on the market as of 2017. You’ll probably need an upconverter to get down to the 80m band, so you might as well build that while you’re at it.

Military Satellite Goes Civilian

Space may be the final frontier, but that doesn’t mean we all get to explore it. Except, perhaps by radio, as the US Air Force has just demobbed a satellite and handed it over to the public to use. FalconSAT-3 was built and used by students at the US Air Force Academy (USAFA) as part of their training, then launched into orbit in 2007. It’s still going 10 years later, but the USAFA is building and launching more satellites, so they don’t need FalconSAT-3. Rather than trash it, they have turned off the military bits and and are allowing radio amateurs to use it.

Continue reading “Military Satellite Goes Civilian”

A Fully Featured, Fifty Dollar QRP Radio

QRP radio operators try to get maximum range out of minimal power. This term comes from the QRP Q-code, which means “reduce power.” For years, people have built some very low-cost radios for this purpose. Perhaps the best known QRP kit is the Pixie, which can be found for less than $3 on eBay.

The QCX is a new DIY QRP radio kit from QRP Labs. Unlike the Pixie, it has a long list of features. The QCX operates on the 80, 60, 40, 30, 20, or 17 meter bands at up to 5W output power. The display provides tuning information, an S-meter, and a CW decoder. An on-board microswitch functions as a basic Morse key, and external Iambic or straight keys are also supported. An optional GPS can be used as a frequency reference.

The radio is based around the Silicon Labs Si5351A Clock Generator, a PLL chip with three clock outputs ranging from 2.5 kHz to 200 MHz. The system is controlled by an Atmel ATmega328P.

Demand for the kit has been quite high, and unfortunately you’ll have to wait for one. However, you can put down your $49 and learn Morse code while waiting for it to ship. While the project does not appear to be open source, the assembly instructions [PDF warning] provide a full schematic.

Satellite Tracking With Friends

If you’re in the mood to track satellites, it’s a relatively simple task to look up one of a multitude of websites that can give you a list of satellites visible from your location. However, if you’re interested in using satellites to communicate with far-flung friends, you might be interested in this multi-point satellite tracker.

[Stephen Downward VA1QLE] developed the tracker to make it easier to figure out which satellites would be simultaneously visible to people at different locations on the Earth’s surface. This is useful for amateur radio, as signals can be passed through satellites with ham gear onboard (such as NO-44), or users can even chat over defunct military satellites.

[Stephen] claims the algorithm is inefficient, but calculations are made in a matter of a few seconds, so we’re not complaining. While it was originally designed for just two stations, it works with a near-infinite number of points. [Stephen] recommends verifying the tracks with another tool once calculated to ensure accuracy. The tool is accessible here, and the code is up on GitHub for your perusal.

Perhaps now you need a cost-effective satellite-tracking antenna? [Paul] has you covered.