Category Archives: dipole

The Internet of Non-Electronic Things

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The bill of materials for even the simplest IoT project is likely to include some kind of microcontroller with some kind of wireless module. But could the BOM for a useful IoT thing someday list only a single item? Quite possibly, if these electronics-less 3D-printed IoT devices are any indication.

While you may think that the silicon-free devices described in a paper (PDF link) by University of Washington students [Vikram Iyer] and [Justin Chan] stand no chance of getting online, they’ve actually built an array of useful IoT things, including an Amazon Dash-like button. The key to their system is …read more

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Slinky Walks Down Stairs and Picks up 80m Band

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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 …read more

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[Jeri] Builds a Magnetic Loop Antenna

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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

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Snazzy Balun Lets Ham Use Off-The-Shelf Coax

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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

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Old Rabbit Ears Optimized for Weather Satellite Downlink

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Communicating with a satellite seems like something that should take a lot of equipment. A fancy antenna and racks full of receivers, filters, and amplifiers would seem to be the entry-level suite of gear. But listening to a weather satellite with an old pair of rabbit ears and an SDR dongle? That’s a thing too.

There was a time when a pair of rabbit ears accompanied every new TV. Those days are gone, but [Thomas Cholakov (N1SPY)] managed to find one of the old TV dipoles in his garage, complete with 300-ohm twinlead and spade connectors. He put it to …read more

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