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

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FM Snake Feeds Off Radio Waves

[Eric Brasseur] built a radio-detecting snake that consists of a LED that lights up when around reasonably strong radio waves. Near an FM radio mast you’ll find a huge amount of waste energy being dumped out in the 88 to 108 MHz range.

[Eric]’s rig consists of a pair of 1N6263 Schottky diodes, flip-flopped with one set of ends soldered to the antenna and the other ends soldered to the leads of the LED with about a foot of wire in between. The antenna can be a single wire as the diodes are soldered together. This one is around 4 …read more http://pje.fyi/PrvQyH

Paul Jacob Evans

Piezomagnetic Trick Shrinks 2.5 GHz Antennas

To a ham radio operator used to “short”-wave antennas with lengths listed in tens of meters, the tiny antennas used in the gigahertz bands barely even register. But if your goal is making radio electronics that’s small enough to swallow, an antenna of a few centimeters is too big. Physics determines plausible antenna sizes, and there’s no way around that, but a large group of researchers and engineers have found a way of side-stepping the problem: resonating a nano-antenna acoustically instead of electromagnetically.

Normal antennas are tuned to some extent to the frequency that you want to pick up. Since …read more http://pje.fyi/PnbgKx

Paul Jacob Evans

ESP32 WiFi Hits 10km with a Little Help

[Jeija] was playing with some ESP32s and in true hacker fashion, he wondered how far he could pull them apart and still get data flowing. His video answer to that question covers the Friis equation and has a lot of good examples of using the equation, decibels, and even a practical example that covers about 10km. You can see the video below.

Of course, to get that kind of range you need a directional antenna. To avoid violating regulations that control transmit power, he’s using the antenna on the receiving end. That also means he had to hack the ESP32 …read more http://pje.fyi/NtTtLV

Paul Jacob Evans