Since I am planning to resume this blog, I thought I’d share a fairly recent project. For a magnetic loop antenna build, I needed a variable capacitor that can handle relatively high voltages. These can be somewhat hard to come across today, and you have to work with what you can find on eBay voltage and capacitance wise. That’s why I came up with a variable capacitor that can be mostly 3D-printed, with the addition of some hardware store parts….
I am currently working on a project that requires me to switch signals in the range of 1-30MHz. I could probably get away with using regular relays, but they’d be rather noisy as I have about 10 signals that need to be switched at the same time. Reed relays would be more quiet, but they can be rather expensive and often have only one contact. I also wanted to avoid any special ICs such as off-the-shelf RF switches or PIN-diodes…
I recently built a simple AM receiver for listening to shortwave radio. The circuit uses just 4 transistors in total, can be built on a breadboard and works pretty well despite it’s simplicity. It works as a regenerative receiver, which means that some of the amplified RF is fed back to the input. This greatly increases sensitivity and selectivity at the cost of having an extra potentiometer that has to be tuned, since too much feedback will cause oscillation. Another…