To look at the wave forms, I use the PC Mic. input, and Audacity, that 
displays the wave forms on the screen and allows saving and viewing 4 
different samples. The receiver is just a simple photo diode, so not to 
filter the carrier. When pointing the Directv TV remote and hitting a 
key (say "3"), there is a definite square  wave with slight sloping 
rises and falls. There  is flat tops and bottoms. Using a typical (have 
tried more than a few) remote, the high has a carrier with say 8 or 15 
cycles of a saw tooth superimposed. 

I guess it would be possible to recognize the digital identifier of the 
Directv, and then sen eithe a square or carrier signal, but that is much 
more work, unless someone has done it previously and all necessary is to 
port the application, of course do only what is legal. :)

Barry Gershenfeld wrote:
> I think you're going to have to discover how that thing communicates
> "without modulation".  ;-)  I suspect you're referring to the 38KHz signal
> as the "modulation".  (Probably should call it the "carrier").  But any
> attempt at straight-through analog amplification is going to be plagued by
> the noise from stray lights as you pointed out.  So you're going to have to
> discover what the receiver is looking for, and detect, and repeat that, much
> as the previous scheme did.
>
> So, maybe it uses baseband codes without a carrier?  My first IR control
> from a TV made in 1976 by GE used discrete frequencies in the 40-50KHz
> range.  So the receiver had to decide which frequency you were throwing at
> it.
>   
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist