9 Aug
2008
9 Aug
'08
6:56 p.m.
der Mouse wrote about the Telebit Trailblazer:
That's interesting! I knew it used hundreds of
carriers, but I didn't
know even the higher-frequency ones ran at low baud rates - and
definitely didn't know that they all changed in sync (as is necessary
to make "7 baud" fair).
They do all change in sync. The modulation and demodulation are
performed using an FFT. That was important to making the original
Trailblazer cost-effective, because it was able to trade off using a
little more memory for needing less DSP computation, as compared to
running hundreds of separate QAM modulators or demodulators.
The rate isn't exactly 7 Hz, but it's somewhere close to that.
Eric