Sferics, Whistlers, and the Dawn Chorus: Listening to Earth Music on VLF

We live in an electromagnetic soup, bombarded by wavelengths from DC to daylight and beyond. A lot of it is of our own making, especially further up the spectrum where wavelengths are short enough for the bandwidth needed for things like WiFi and cell phones. But long before humans figured out how to make their own electromagnetic ripples, the Earth was singing songs at the low end of the spectrum. The very low frequency (VLF) band abounds with interesting natural emissions, and listening to these Earth sounds can be quite a treat.

Long, Long Waves

The VLF band is roughly …read more http://pje.fyi/PzYGw6

Paul Jacob Evans

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[Jeri] Builds a Magnetic Loop Antenna

Most new hams quickly learn that the high-frequency bands are where the action is, and getting on the air somewhere between 40- and 160-meters is the way to make those coveted globe-hopping contacts. Trouble is, the easiest antennas to build — horizontal center-fed dipoles — start to claim a lot of real estate at these wavelengths.

So hacker of note and dedicated amateur radio operator [Jeri Ellsworth (AI6TK)] has started a video series devoted to building a magnetic loop antenna for the 160- and 80-meter bands. The first video, included after the break, is an overview of the rationale behind …read more http://pje.fyi/PypStJ

Paul Jacob Evans

Scratch That SDR!

When you think of a software defined radio, what language might you consider reaching for to create the software part of the equation? C? C++, maybe?

How about Scratch?

“What, Scratch as in the visual programming language aimed at young people?”, we hear you cry incredulously. It’s not exactly the answer you’d expect for an SDR, but thanks to [Andrew Back]’s work there is now ScratchRadio, a set of Scratch extensions for software defined radio. Why on earth do this? The aim is to lower the barrier to entry for software defined radio as far as possible, and to place …read more http://pje.fyi/PyGVn5

Paul Jacob Evans

LoRa Is the Network

We’ve become used to seeing LoRa appearing in projects on these pages, doing its job as a low-bandwidth wireless data link with a significant range. Usually these LoRa projects take the form of a client that talks to a central Internet connected node, allowing a remote wireless-connected device to connect through that node to the Internet.

It’s interesting then to see a modest application from [Mark C], a chat application designed to use a set of LoRa nodes as a peer-to-peer network. In effect LoRa becomes the network, instead of simply being a tool to access it. He optimistically describes …read more http://pje.fyi/PxSVP6

Paul Jacob Evans

Snazzy Balun Lets Ham Use Off-The-Shelf Coax

It’s a dilemma many hams face: it’s easy to find yourself with a big spool of RG-11 coax cable, usually after a big cable TV wiring project. It can be tempting to use it in antenna projects, but the characteristic impedance of RG-11 is 75 Ω, whereas the ham world is geared to 50 Ω. Not willing to waste a bounty of free coax, one ham built a custom 1:1 current balun for a 75 Ω dipole.

Converting between balanced and unbalanced signals is the job of a balun, and it’s where the device derives its name. For hams, baluns …read more http://pje.fyi/Pw3hQ8

Paul Jacob Evans

The Early Bird Repairs a Slug

When faced with a problematic Bird slug, [Chuck Martin] didn’t give up. He pecked away at the slug and brought us all along for the ride. If that sentence didn’t make sense to you, read on! Anyone who’s been to a hamfest has seen a Bird meter. The Bird Model 43 watt meter is the defacto standard for measuring transmitter power in-line. Bird meters don’t just work from DC to light though. In fact, the model 43 itself is just a bit of transmission line and a meter movement.  The magic happens inside the swappable measurement element. These elements, affectionately …read more http://pje.fyi/PvT0XX

Paul Jacob Evans

Retrotechtacular: Radio to Listen to When you Duck and Cover

CONELRAD may sound like the name of a fictional android, but it is actually an acronym for control of electronic radiation. This was a system put in place by the United States at the height of the cold war (from 1951 to 1963) with two purposes: One was to disseminate civil defense information to the population and, also, to eliminate radio signals as homing beacons for enemy pilots.

How CONELRAD Worked

Here’s how it worked: In case of an attack, certain key stations were notified. They would use a very simple sequence to indicate there was an alert. All FCC-licensed …read more http://pje.fyi/Pv9h2f

Paul Jacob Evans