Aluminum Foil 20 Cm Antenna For 10 M Operation

July 2, 2022 by Chris Lott 11 Comments

[David], DL1DN, is an Amateur Radio enthusiast with a penchant for low-power (QRP) portable operations. Recently he was out and about, and found that 10 m propagation was wide open. Not discouraged by having forgotten his antenna, he kludges up a makeshift one using a 20 cm length of aluminum foil (see video demonstration below the break). [David] wasn’t completely unprepared, as he did have the loading coil for his portable 20 m antenna, but was missing the telescoping whip. He calculated the whip length should be around 20 cm for 10 m operation, and crinkles up a sheet of foil the approximate length. He tunes it to length by rolling the tip to shorten the “whip” until he gets an SWR minimum.

Schematic of [David]’s QRP Portable Whip Antenna

[David] describes this style of portable antenna in another video, using a more conventional telescoping whip as the radiating element. The loading coil is built from common PVC pipe and insulated wire. While these aren’t necessarily the most efficient antennas, they can do the trick when portability is a major concern. For a different approach, here’s a QRP Hackaday.io portable antenna project using a magnetic loop antenna. But for the ultimate in QRP, check out this transmitter we wrote about in 2013 that uses only voice power to operate.

What are some unusual items you’ve used as makeshift antennas? Let us know in the comments below. Thanks to [mister35mm] for submitting this to our tip line.

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A GPS Frequency Standard For When The Timing Has To Be Right

June 29, 2022 by Jenny List 10 Comments

A metrology geek will go to extreme lengths to ensure that their measurements are the best, their instruments the most accurate, and their calibration spot-on. There was a time when for time-and-frequency geeks this would have been a difficult job, but with the advent of GPS satellites overhead carrying super-accurate atomic clocks it’s surprisingly easy to be right on-frequency. [Land-boards] have a GPS 10 MHz clock that’s based around a set of modules.

Since many GPS modules have a 10 MHz output one might expect that this one to simply hook a socket to the module and have done, but instead it uses another of their projects, a fast edge pulse generator with the GPS output as its oscillator, as a buffer and signal conditioner. Add to that an QT Py microcontroller board to set up the GPS, and there you have a standalone 10 MHz source to rival any standard. Full details can be found on the project’s wiki, and the firmware can be found on GitHub.

Careful with your exploration of standard frequencies, for that can lead down a rabbit hole.

Shielding A Cheap RTL-SDR Stick

June 29, 2022 by Jenny List 22 Comments

Even though not every Hackaday reader is likely to be a radio enthusiast, it’s a fair guess that many of you will have experimented with an RTL-SDR USB dongle by now. These super-cheap devices are intended for digital TV reception and contain an RTL2832 chip, which with the proper software, can be pushed into service as a general purpose software defined radio receiver. For around $10 USD they’re fantastic value and a lot of fun to play with, even if they’re not the best radio ever. How to improve the lackluster performance? One of the easiest and cheapest ways is simply to shield it from RF noise, which [Alan R] has done with something as mundane as a tubular fizzy orange tablet container.

This is probably one of the simpler hacks you’ll see on this site, as all it involves is making an appropriate hole in the end of the tube and shielding the whole with some aluminium foil sticky tape. But the benefits can be seen immediately in the form of reduced FM broadcast band interference, something that plagues the cheaper dongles.

Perhaps the value in this hack aside from how easy it is on a cheap dongle is that it serves to remind us some of the benefits of paying a little extra for a better quality device. If you’d like to know more about RTL-SDR improvements, it’s a topic we covered in detail back in 2019 when we looked at seven years of RTL-hackery.

An Epic Tale Of Pirate Radio In Its Golden Age

June 28, 2022 by Jenny List 29 Comments

With music consumption having long ago moved to a streaming model in many parts of the world, it sometimes feels as though, just like the rotary telephone dial, kids might not even know what a radio was, let alone own one. But there was a time when broadcasting pop music over the airwaves was a deeply subversive activity for Europeans at least, as the lumbering state monopoly broadcasters were challenged by illegal pirate stations carrying the cutting edge music they had failed to provide. [Ringway Manchester] has the story of one such pirate station which broadcast across the city for a few years in the 1970s, and it’s a fascinating tale indeed.

It takes the form of a series of six videos, the first of which we’ve embedded below the break. The next installment is placed as an embedded link at the end of each video, and it’s worth sitting down for the full set.

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Designing A LoRa Gateway During A Part Shortage

June 28, 2022 by Tom Nardi 14 Comments

It’s fair to say that right now is probably the worst possible time you could choose to design a new piece of hardware. Of course the reality is that, even in the middle of a parts shortage that’s driving the cost of many components through the roof (if you can even find them), we can’t just stop building new devices. In practice, that means you’ll need to be a bit more flexible when embarking on a new design — it’s like the Stones said: “You can’t always get what you want / But if you try sometime you’ll find / You get what you need”

For [Ryan Walmsley], that meant basing his new outdoor LoRa gateway on the ubiquitous Raspberry Pi was a non-starter. So what could he use in its place? The software situation for the Nano Pi Duo looked pretty poor, and while the Onion Omega 2+ was initially compelling, a bug in the hardware SPI seemed to take it out of the running. But after more research, he found there was a software implementation that would fit the bill. Continue reading “Designing A LoRa Gateway During A Part Shortage” →

Homebrew Radio Telescope Bags Pulsar

May 25, 2022 by Dan Maloney 11 Comments

When one mulls the possibility of detecting pulsars, to the degree that one does, thoughts turn to large dish antennas and rack upon rack of sensitive receivers, filters, and digital signal processors. But there’s more than one way to catch the regular radio bursts from these celestial beacons, and if you know what you’re doing, a small satellite dish and an RTL-SDR dongle will suffice.

Granted, [Job Geheniau] has had a lot of experience exploring the radio universe. His website has a long list of observations and accomplishments achieved using his “JRT”, or “Job’s Radio Telescope.” The instrument looks like a homebrewer’s dream, with a 1.9-m satellite TV dish and precision azimuth-elevation rotator. Behind the feedhorn are a pair of low-noise amplifiers and bandpass filters to massage the 1,420 MHz signal that’s commonly used for radio astronomy, plus a Nooelec Smart SDR dongle and an Airspy Mini. Everything is run via remote control, as the interference is much lower with the antenna situated at his family’s farm, 50 km distant from his home in The Hague.

As for the pulsar, bloodlessly named PSR B0329+54, it’s a 5-million-year-old neutron star located in the constellation of Camelopardalis, about 3,500 light-years away. It’s a well-characterized pulsar and pulses at a regular 0.71452 seconds, but it’s generally observed with much, much larger antennas. [Job]’s write-up of the observation contains a lot of detail on the methods and software he used, and while the data is far from clear to the casual observer, it sure seems like he bagged it.

We’ve seen quite a few DIY radio astronomy projects before, both large and small, but this one really impresses with what it accomplished.

[via RTL-SDR.com]

VR Spectrum Analyzer

May 21, 2022 by Al Williams 5 Comments

At one point or another, we’ve probably all wished we had a VR headset that would allow us to fly around our designs. While not quite the same, thing, [manahiyo831] has something that might even be better: a VR spectrum analyzer. You can get an idea of what it looks like in the video below, although that is actually from an earlier version.

The video shows a remote PC using an RTL dongle to pick up signals. The newer version runs on the Quest 2 headset, so you can simply attach the dongle to the headset. Sure, you’d look like a space cadet with this on, but — honestly — if you are willing to be seen in the headset, it isn’t that much more hardware.

What we’d really like to see, though, is a directional antenna so you could see the signals in the direction you were looking. Now that would be something. As it is, this is undeniably cool, but we aren’t sure what its real utility is.

What other VR test gear would you like to see? A Tron-like logic analyzer? A function generator that lets you draw waveforms in the air? A headset oscilloscope? Or maybe just a giant workbench in VR?

A spectrum analyzer is a natural project for an SDR. Or things that have SDRs in them.

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