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Wednesday, April 13, 2011

Homebrew Two Dollar Oscilloscope

This is from a short article in the April 1997 issue of Electric Radio magazine. The author is Bob Dennison, W2HBE. Bob is a real genius, and the author of many inspirational articles in ER.

The Sundt Engineering Company of Chicago was advertising this kind of device in the June 1936 issue of Short Wave Craft Magazine. Only two dollars (but that was big money in 1936). From Bob's article: "When the transmitter is modulated with a single audio tone, the waveform of the modulated carrier will be seen. By varying the motor speed (horizontal scan rate) the pattern can be synchronized or made to stand still. Percentage modulation is readily estimated by simple inspection of the display."

So here we have the perfect minimalist 'scope to go with a minimalist AM transmitter!


  1. I like it. That's $31 in today's US money. You could get a little DC motor, pot, neon and mirror for much less than that at any decent surplus store or even Radio Shack. But that now-precious variable cap in the tuned circuit had better be in your junk box. Can a low-power transmitter induce the 80-100V it takes to fire a neon?

  2. Maybe use an LED instead of the neon tube?

  3. Shhhhhh!!! Don't tell anyone that they can make a scope for $3 - I'll be out of a job!!!

  4. Who's going to be the first to construct this using stone knives and bear skins. Someone in an underground lair perhaps?

    73.......Steve Smith WB6TNL
    "Snort Rosin"

  5. Hi Bill,
    You were correct. When I got my Novice ticket back in 1957.....(wow!)
    It was good only for 12 months.
    You could not renew...nor re-apply for the Novice class. You either upgraded by testing before FCC examiner or you were out. Don't know when they expanded to two years, but for me it was one year.
    George Allgood
    Walhalla, SC

  6. Interesting - it reminded me of all kinds of elecromechanical oscilloscope designs I remember seeing in an ancient electrical engineering book I used to have when I was a kid. I've never seen one of the machines they were talking about.


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