The Poynting Vector Antenna

Radio amateurs are inventive people, and though not all of them choose to follow it there is a healthy culture of buildng radio equipment among them. In particular the field of antennas is where you’ll find a lot of their work, because the barrier to entry can be as low as the cost of a reel of wire.

Over the years a number of innovative antenna designs have come from radio amateurs’ experimentation, and it’s one of the more recent we’d like to share with you today following a [Southgate ARC] story about a book describing its theory (Here’s an Amazon link to the book itself). The Poynting Vector antenna has been one of those novel designs on the fringes for a while now, it has been variously described as the “Super-T”, or the “flute”. Its party piece is tiny dimensions, a fraction of the size of a conventional dipole, and it achieves that by the interaction between a magnetic field across the plates of a capacitor in a tuned circuit and the electric field between a very short pair of dipole radiators. The trade-off is that it has an extremely high Q and thus a narrow bandwidth, and since its feeder can become part of its resonant circuit it is notoriously difficult to match to a transmitter. [Alan MacDonald, VE3TET] and [Paul Birke, VE3PVB] have a detailed page on the development of their Poynting antenna which takes the reader through the details of its theory and the development of their practical version.

In the roof space above the room in which this is being written there hangs a traditional dipole for the 20m amateur band. Though it is a very effective antenna given that it is made from a couple of pieces of wire and a ferrite core it takes most of the length of the space, and as we’re sure Hackaday readers with callsigns will agree a relatively tiny alternative is always very welcome.

If antennas are a mystery to you then we’d suggest you read an introduction to antenna basics to get you started.

Get On 10 GHz For 3 Euros

A frequent complaint you will hear about amateur radio is that it is a chequebook pursuit. Of course you can work the incredible DX if you spend $20k on a high-end radio, big antenna, and associated components. The reality is though that because it’s such a multi-faceted world there are many ways into it of which the operator with the shiny rig is taking only one.

On the commonly used HF and VHF bands at the lower end of the radio spectrum you will definitely find chequebook amateurs of the type described in the previous paragraph. But as you ascend into the microwave bands there are no shiny new radios on the market, so even the well-heeled licensee must plow their own furrow and build their own station.

You might think that this would remain a chequebook operation of a different type, as exotic microwave devices are not always cheap. But in fact these bands have a long history of extremely inexpensive construction, in which skilled design and construction as well as clever re-use of components from satellite TV systems and Doppler radar modules play a part. And it is a project following this path that is our subject today, for [Peter Knol, PA1SDB] has repurposed a modern Doppler radar module as a transmitter for the 10GHz or 3cm amateur band (Google Translate version of Dutch original). The best bit about [Peter]’s project is the price: these modules can be had for only three Euros.

Years ago a Doppler module would have used a Gunn diode in a waveguide cavity and small horn, usually with an adjacent mixer diode for receiving. Its modern equivalent uses a transistor oscillator on a PCB, with a dielectric resonator and a set of patch antennas. There is also a simple receiver on board, but since [Peter] is using a converted ten-Euro satellite LNB for that task, it is redundant.

He takes us through the process of adjusting the module’s frequency before showing us how to mount it at the prime focus of a parabolic antenna. FM modulation comes via a very old-fashioned transformer in the power feed. He then looks at fitting an SMA connector and using it for more advanced antenna set-ups, before experimenting with the attenuating properties of different substances. All in all this is a fascinating read if you are interested in simple microwave construction.

The result is not the most accomplished 10 GHz station in the world, but it performs adequately for its extremely low price given that he’s logged a 32 km contact with it.

Though we cover our fair share of amateur radio stories here at Hackaday it’s fair to say we haven’t seen many in the microwave bands. If however you think we’ve been remiss in this area, may we point you to our recent coverage of a microwave radio receiver made from diamond?

Via Southgate ARC.

Demystifying Amateur Radio Callsigns

Regular Hackaday readers will be familiar with our convention of putting the name, nickname, or handle of a person in square brackets. We do this to avoid ambiguity as sometimes names and particularly nicknames can take unfamiliar forms that might be confused with other entities referred to in the text. So for example you might see them around [Bart Simpson], or [El Barto]. and occasionally within those brackets you’ll also see a capitalised string of letters and numbers after a name. For example the electronic music pioneer [Bob Moog, K2AMH], which most of you will recognise as an amateur radio callsign.

Every licenced radio amateur is issued one by their country’s radio authority as a unique identifier, think of it as similar to a car licence plate. From within the amateur radio bubble those letters and numbers can convey a significant amount of information about where in the world its user is located, when they received their licence, and even what type of licence they hold, but to outsiders they remain a mysterious and seemingly random string. We’ll now attempt to shed some light on that information, so you too can look at a callsign in a Hackaday piece or anywhere else and have some idea as to its meaning.

Continue reading “Demystifying Amateur Radio Callsigns”

Five-Watt SDR Transceiver for Hams

The availability of cheap SDR hardware created a flourishing ecosystem for SDR software, but a lot of the hardware driving the revolution was still “cheap”. In the last few years, we’ve seen quality gear replacing the TV dongles in many setups, and down-converters designed for them to allow them to work on the ham bands.

But something that’s purpose-built might be a better option if ham radio, particularly the shortwave portion thereof, is your goal. First off, you might want to transmit, which none of the TV dongles allow. Then, you might want a bit of power. Finally, if you’re serious about short-wave, you care more about the audio quality than you do immense bandwidth, so you’re going to want some good filters on the receiving end to help you pull the signal out of all the noise.

rs-hfiq_block_diagram_featuredThe RS-HFIQ 5 W SDR transceiver might be for you. It’s up on Kickstarter right now, and it’s worth looking at if you want a fully open source (schematics, firmware, and software) shortwave SDR rig. It’s also compatible with various open frontends.

The single-board radio isn’t really a full SDR in our mind — it demodulates the radio signal and sends a 96 kHz IQ signal across to your computer’s soundcard where it gets sampled and fully decoded. The advantage of this is that purpose-built audio rate DACs have comparatively high resolution for the money, but the disadvantage is that you’re limited to 96 kHz of spectrum into the computer. That’s great for voice and code transmissions, but won’t cut it for high-bandwidth data or frequency hopping applications. But that’s a reasonable design tradeoff for a shortwave.

Still, an SDR like this is a far cry from how simple a shortwave radio can be. But if you’re looking to build up your own SDR-based shortwave setup, and you’d like to hack on the controls more than on the radio itself, this looks like a good start.

Resurrection — Pressing WW2 Radio Equipment Back into Service

Mass production was key to survival during the Second World War. So much stuff was made that there continues to be volumes of new unpacked stuff left over and tons of used equipment for sale at reasonable prices. Availability of this war surplus provided experimenters in the mid 20th century with access to high performance test equipment, radio equipment, and high quality components for the first time.

Even today this old stuff continues to motivate and inspire the young generations because of its high build quality, unique electro-mechanical approaches, and overall innovative designs which continue to be relevant into the 21st century. In this post we will show you how to get started in the hobby of resurrecting WW2 radio equipment and putting it back on the air.

Continue reading “Resurrection — Pressing WW2 Radio Equipment Back into Service”

Hams in Space Part 2: The Manned Spaceflights

Whether it’s trying to make contacts across the planet with a transmitter that would have a hard time lighting an LED, or blasting signals into space and bouncing them off the moon, amateur radio operators have always been on the forefront of communications technology. As mankind took to space in the 1950s and 1960s, hams went along for the ride with the first private satellites. But as successful as the OSCAR satellites were, they were still at best only beacons or repeaters in space. What was needed was the human touch – a real live operator making contacts with people on the ground, showing the capabilities of amateur radio while generating public interest in the space program. What was needed was a ham in space. Continue reading “Hams in Space Part 2: The Manned Spaceflights”

The BITX Transceiver Comes Of Age

There was a time when the idea of building your own single-sideband transceiver was too daunting for all but the most hardcore of amateur radio constructors. After all the process of creating SSB is complex enough in itself without adding the extra complexity of a receiver and the associated switching circuitry.

In 2003 an Indian radio amateur, [Ashhar Farhan], [VU2ESE] changed all that. His BitX SSB transceiver used a bidirectional amplifier design and readily available components such that it could be built by almost anyone using dead bug construction techniques for an extremely reasonable price.

Over the years since [Ashhar] first published his circuit, his design has been taken and enhanced, been presented in kit form, and extended to other bands by multiple other radio amateurs. Until now though it seems as though he himself has taken very little advantage of his work.

It is therefore with great interest that we note a new 40-meter BitX transceiver on the market from a company founded by the man himself. The transceiver itself is an Indian-assembled PCB with an updated circuit using a 12 MHz IF, varicap tuning, and large surface-mount components for easy modification. Just as with the original circuit, there is a full technical run-down of its operation should you wish to build one yourself. For a rather impressive $45 though you might wish to put down the soldering iron, it looks very much worth the wait for international postage.

We don’t often feature commercial product launches here on Hackaday, though we are besieged by people trying to persuade us to do so. So why this one? When the creator of a design that has been as significant as the BitX has been to its community of builders releases a new version it is newsworthy in itself, and if they are commercializing their work then they deserve that reward.

We’ve featured the BitX here in the past, with a rather impressive dead-bug build, and a look at a multiband version. We’re sure that this design thread has more to deliver, and look forward to more.

Thanks [WB9FLW] for the tip.