[Laser] stable audio oscillator?

David D. Rea [email protected]
Thu, 10 Apr 2003 19:08:40 -0400


If you only need a few hundred Hz, you could use a microcontroller with
a crystal oscillator. You could just program it to clock an I/O pin on
and off every [insert desired number here] machine cycles.

If you're using a pen pointer, you can then just use a NPN transistor to
pull down the input rail of the pointer, providing MCW at whatever rate
you want.

If you wanted to get real spiffy, you could hook a keyboard and display
up to the microcontroller, and have it do everything for ya!

Dave Rea
RIT
Rochester, NY

On Thu, 2003-04-10 at 18:38, Andrew T. Flowers, K0SM wrote:
> I'm not really sure whom to ask about this, but I'm guessing that 
> someone has run into a similar problem at one time or another...
> 
> I'm building a laser communication system and I'm looking at different 
> modulation schemes for the transmitter.  I'd like to try QRSS CW--that's 
> CW in 0.5wpm or even less, using DSP to show the elements on the screen 
> using spectran or other analysis program.  I thought about keying the 
> laser on and off into a 12vdc fan to create a squarewave tone.  It works 
> fine for normal speed CW, but the frequency drift is +/- 10Hz or so. 
>  For QRSS to be effective, I need rock-solid stability, preferably less 
> than 100 millihertz/min or better.  Any ideas here?  I'd like to keep it 
> cheap.  Is there some version of the 555 timer do this with good 
> components?  I was also thinking of getting some ovenized xtal thing in 
> the low RF range and then dividing down.
> 
> Ideas??
> 
> Andy, K0SM
> 
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