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Re: [Discuss-gnuradio] VGA-based DVB-T modulator

From: Seth David Schoen
Subject: Re: [Discuss-gnuradio] VGA-based DVB-T modulator
Date: Mon, 13 Jun 2005 16:45:15 -0700
User-agent: Mutt/1.5.9i

Johnathan Corgan writes:

> Seth David Schoen wrote:
> >Someone proposed this a while ago, but Fabrice Bellard (who is also
> >responsible for cool stuff like the tcc compiler, which lets you use
> >C as a scripting language and lets the Linux kernel compile itself
> >at boot time) has used a VGA card's DAC as an RF modulator to produce
> >a valid DVB-T signal.
> I sure wish I could remember where to find it, but I've seen 
> demonstrated a program that would generate valid AM waveforms by 
> displaying certain pictures on a video screen.  You'd enter a target 
> frequency (I think in the HF range) and choose a MIDI sound file, and it 
> would "modulate" the CRT display to emit RFI at that frequency with the 
> tones riding as AM modulation.  Very spooky.  It was a demonstration of 
> the security hazards associated with CRT displays (TEMPEST stuff) in a 
> very palpable way.

Probably Tempest for Eliza:


There's yet another similar project that I would like to track down
that was using a VGA card.

Does anyone here know if the VGA cards prevent you from controlling
the DAC durinng the blanking intervals?  Are the blanking intervals
implemented in hardware or in software?

Seth David Schoen <address@hidden> | Very frankly, I am opposed to people
     http://www.loyalty.org/~schoen/   | being programmed by others.
     http://vitanuova.loyalty.org/     |     -- Fred Rogers (1928-2003),
                                       |        464 U.S. 417, 445 (1984)

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