A motley collection of ideas
Homemade circuits, experiments, tinker-friendly electronic ideas, and and things related to amateur radio.
Spotters, SWL (shortwave listening) enthusiasts, and amateur radio operators all enjoy listening to aircraft communications — and nowadays, even drone pilots find it useful to monitor air traffic. A good handheld airband transceiver easily costs well over a hundred thousand forints, whereas the device described here is dirt cheap by comparison. Of course, it’s not … Read more
The handheld meter has been a staple in almost every technician’s toolkit for nearly 100 years. Today, the majority of handheld meters have digital displays. However, until the 1970s, most meters featured analog readouts. These were typically multimeters capable of measuring voltage, current, resistance, and occasionally capacitance and frequency. “Pocket watch”-style measuring instruments were popular … Read more
The purpose of this project is to extend the range of an older (and more affordable) frequency counter into the VHF and UHF bands. The idea was inspired by an article published in Rádiótechnika (1990/7, pp. 341–342), although the original circuit was designed by Zeljko Bozic, S52ZB, and later published in a 2006 issue of … Read more
Sometimes I find myself wondering which of my portable digital voltmeters I can actually trust. The old 4½-digit M4650? The Fulke? Or the younger METEX? (Okay, I have one from Lidl too, but that’s not even a question.) Generally, they all show pretty similar values, and I rarely need better than 1–2% accuracy—but it still … Read more
I needed a compact power supply capable of providing roughly 5–20 V DC and 12–16 V AC. Because an AC output was required, I chose a conventional transformer—similar to those used in alarm control units and intercom systems. This project was inspired by the Chordless Lab Power Supply on Thingiverse. DC Section The DC side is quite simple: a … Read more
The phenomenon of resonance has many examples in physics, engineering, and everyday life, and the reed frequency meter is one of them. Surprisingly, such instruments are still in use here and there, although they are certainly considered rarities today. I picked up this specimen, manufactured in 1961, for a few coins at a swap meet. … Read more
My better half has a weakness for weather stations, and she especially likes this old piece. It’s not particularly smart, not particularly pretty, but it has a “frog”, which makes up for everything. It’s a cheap LIDL model — even the first one we bought didn’t pick up the signal from the external sensor. They replaced … Read more
It’s well known that bats use their sonar to navigate their surroundings with remarkable precision. As part of this ability, they emit powerful ultrasonic sounds that are characteristic of each species. These sounds are inaudible to the human ear, but with a simple device, we can detect them — which can be great fun and … Read more
This stairwell lighting timer switch was rescued for me from a building by a friendly electrician acquaintance of mine, Sándor Auffenberg. It had been removed because it was “misbehaving,” but it later turned out to be perfectly fine. According to its label, it was manufactured in 1991—so it’s 30 years old… I’ve written before about … Read more
In 2014, the Csepel spark telegraph station turned one hundred years old. The equipment transmitted messages from both Béla Kun and Lenin. I decided that for the 105th anniversary, I would build a spark transmitter myself. Csepel spark telegraph radio station The construction of the Csepel spark telegraph radio station, which marked the beginning of … Read more