[Laser] Thoughts on receiver design

[Andrew T. Flowers, K0SM]

wa4qal@ix.netcom.com wrote:

>I haven't frequency tested my laser pointers yet, but they
>don't seem to have any trouble responding at 800 Hz, and
>based on the shape of the waveform at that frequency, I
>expect that they'll go a lot higher.  Laser diodes themselves
>can work well up into the GHz range (or even higher!), but
>the circuitry in a laser pointer to regulate the current to the 
>diodes usually has some capacitors which tend to limit the 
>maximum frequency.  Of course, you could always design 
>your own current regulator to get around the frequency 
>limitations (and, you'll have to if you're going to use raw
>diodes, rather than laser pointers).
>
>  
>
If you go with the really cheap pointers you will find that the "current 
regulator" consists of a 47-ohm chip resistor.  The little laser 
keychain units can be had for around $1/ea off of ebay if you buy in 
quantities of 10 or more.  I they shouldn't have any trouble with being 
modulated into the RF range unless there is some weird capacitance in 
the dye that I don't know about.

Andy K0SM/2