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# How can i convert square wave to sine wave

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#### holax12

##### New Member
I need to convert a square wave to a pure sine wave, how can this be archeived in its simplest form. Thanks

I need to convert a square wave to a pure sine wave, how can this be archeived in its simplest form. Thanks

hi,
What frequency.?

can you define 'pure'?

what sort of power level as well? there are waveform generators that are good at sine waves, but not if you need 15kw

Actually i want to convert the square wave generated from an astable multivibrator to sine wave and use it as a rf generator. The frequency is 100mhz.

Do you have an astable multibrator running @100 MHZ??? I have a multi running a few 10's of KHZ, and I generate a sine wave from it, but I can't even think about running at that freq.

EDIT: for that freq, just use an RF oscillator, and generate the sine wave directly.

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The rf generator i know is LC tank circuit and it is not stable, slight torch on any part usually alter the frequency. So i want to use astable multivibrator to generate stable frequency.

Use an rf generator, and don't touch any of the parts. You aren't going to get an astable multi to run at your frequency.

Thanks for ur reply @ Brownout.

What if i get the astable multi to work at the frequency i want will it work as an rf generator.

Keep torches away from your LC.

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Thanks for ur reply @ Brownout.

What if i get the astable multi to work at the frequency i want will it work as an rf generator.

You won't, so it's a pointless question.

Theoretically (and practically to some extent) if you have a low frequency square wave then you have higher frequency components though at profoundly lower power levels than the fundamental frequency. A filter might help push down the stuff you don't want - leaving the part that you do want. This seems clumsy but it might serve your purpose.

I know in amateur/shortwave radio they used to have a crystal "calibrator) that delivered RF at various specific intervals all over the RF spectrum. I recall seeing some solid-state circuits that I'd guess were square wave generators rich in RF. One would adjust the marker against a known standard like WWV.

Using SMT components it's possible to build an astable multivibrator that'll run at 100MHz.

It's a silly idea though, you're better off using an LC oscillator.

Is this an FM transmitter? In high power output stage of a transmitter a MOSFET in class c is practically making a square wave, often the gate driven by logic IC or MOSFET driver. The LC 'Pi filter' which matches the antenna turns it into a sine wave.

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