Recreating One Of History’s Best Known Spy Gadgets

[Machining and Microwaves] got an interesting request. The BBC asked him to duplicate the Great Seal Bug — the device the Russians used to listen covertly to the US ambassador for seven years in 1945. Turns out they’re filming a documentary on the legendary surveillance device and wanted to demonstrate how it worked.

The strange thing about the bug is that it wasn’t directly powered. It was actually a resonant cavity that only worked when it was irradiated with an external RF energy. Most of the video is background about the bug, with quite a few details revealed. We particularly liked the story of using a software defined radio (SDR) to actually make the bug work.

As you might expect, things didn’t go smoothly. Did they ever get results on camera? Watch the video, and you can find out. This is just the first of six videos he plans to make on the topic, and we can’t wait for future videos that cover the machining and more technical details.

We’ve examined the Theremin bug before. There’s a definite cat-and-mouse dynamic between creating bugging devices and detecting them.

21 thoughts on “Recreating One Of History’s Best Known Spy Gadgets

    1. I hope my new video will help dispel a few of the myths and inaccuracies in much of the published material! New vid is at and a playlist of the whole growing series is here:

      Next up will be the machining vid, then the demonstration vid, then an investigation into where Lev Termen found his inspiration (spoiler: the US Patent Office and during his work for the NKVD while working as a showbiz celeb, entrepreneur and sometime money-launderer (allegedly)

  1. Thank you very much, my thoughts have been more or less along the same line…
    From the video you can find out zilch about the device itself.
    I still would be really interested about more technical details about the whole thing

  2. Found the full BBC documentation; it’s actually about bank cards. Haven’t had time to watch it after already watching this video, but it’s cool that the BBC commissions something that definitely made someone’s day (and probably a bit of their rent) to illustrate backscatter communications :)

    1. Sadly, I didn’t get paid a cent for the 200+ hours the project took, other than travel expenses and hotel stays, but as a result of the programme being on TV and the exposure on Youtube, I’ve had some very interesting collaboration offers and made a little from Adsense revenue plus some very kind Patreon donations. The real motivation was so my mother could tell her friends that her little boy was on the TV with a Professor!

  3. I’ve heard that when a new US embassy was built in Moscow, the russians put all bad transistors an diodes in the concrete to be discovered by the non linear junction detectors. When the americans learned about this by scanning for listening devices, the building was already built. So they had to build another one with americans workers.

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