The Setup

In my setup, I use a Morserino electronic keyer and send the (square-wave) sidetone through a small passive LC-filter, like the one described here by Ralf, DK5BU. Housed within a repurposed peppermint tin from Chicago O’Hare, this homebrew filter performs a critical transformation: converting harsh square waves into smooth sine waves. By dampening the sharp rise and fall transients, it ensures a signal free of key clicks and mitigates bandwidth-spattering transients.

My Testimonial

Although it’s not strictly recommended, this setup with the Morserino actually works well enough, and it’s robust enough for my frequent travels. Regarding the filter: it does what it’s supposed to, though it attenuates the signal quite a bit. In a future version, I plan to couple the inductors better, perhaps by winding them myself. Of course, there’s always room for optimization, but for a few occasional QSOs from a hotel room, it’s pretty decent as is.