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 Post subject: Need a Sine Wave? Ring One Up.
PostPosted: Jun Sun 27, 2021 8:52 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 5177
Location: Melbourne, Florida
I needed a decent 1 MHz sine wave to check calibration on a high bandwidth AF voltmeter. All my signal generators are service grade and none generate anything close to a clean waveform.

It occurred to me that I might be able to get a decent waveform by filtering out the harmonics from my EICO 324 output. I was too lazy to design a special filter so I decided to try a simple tuned circuit. I had a left over coil from a regenerative receiver project and a variable cap from the junk box so I built it up on a board and tried it out. As you can see it's really simple but it gave me a sine wave with harmonics down 45-50 db which was plenty good enough for my use.

There's plenty of room for experimentation with something like this.

RRM


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Simple Tunable Filter.jpg
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