{"id":1521,"date":"2025-06-10T09:38:57","date_gmt":"2025-06-10T08:38:57","guid":{"rendered":"https:\/\/pi4zlb.vrza.nl\/wp\/?p=1521"},"modified":"2025-06-10T09:38:57","modified_gmt":"2025-06-10T08:38:57","slug":"single-tube-sdr-is-a-delightful-mix-of-old-and-new","status":"publish","type":"post","link":"https:\/\/pi4zlb.vrza.nl\/wp\/2025\/06\/10\/single-tube-sdr-is-a-delightful-mix-of-old-and-new\/","title":{"rendered":"Single Tube SDR Is A Delightful Mix Of Old And New"},"content":{"rendered":"
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Software Defined Radio (SDR) is the big thing these days, and why not? A single computer can get rid of a room full of boat anchors, and give you better signal discrimination than all but the best kit. Any SDR project needs an RF receiver, and in this project [mircemk] used a single 6J1 vaccum tube to produce an SSB SDR that combines the best of old and new.\u00a0<\/a><\/p>\n

Single-tube radios are a classic hack, and where a lot of hams got started back in the day, but there is a reason more complicated circuits tend to be used. On the other hand, if you can throw a PC worth of signal processing at the output, it looks like you can get a very sensitive and selective single-sideband (SSB) receiver.<\/p>\n

The 6J1 tube is convenient, since it can run on only 6 V (or down to 3.7 as [mircemk] demonstrates). Here it is used as a mixer, with the oscillator signal injected via the screen grid. Aside from that, the simple circuit consists of a receiving coil, a few resistors and a variable capacitor. How well does it work? Quite well, when paired with a PC; you can judge for yourself in the video embedded below.<\/p>\n

We\u2019ve featured a lot of [mircemk]\u2019s projects over the years, like this handsome OLED VU meter<\/a>, or this frequency analyzer with a VFD\u00a0 <\/a>and even a virtual pinball cabinet made from scraps<\/a>, among many others.<\/p>\n

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