On Aug 1, 2005, at 7:58 AM, Bill Turner wrote:
> RTTY is commonly processed by a digital computer, but the Baudot
> character
> set itself is purely analog.
At some level, all digital modes used over the airwaves are analog,
unless you send baseband Walsh functions or Manchester codes over the
air -- and if you do that, each bit of information will be spread in
the Fourier spectrum (what hams usually call "spectrum") between DC
and "daylight." :-)
At the demodulator level, RTTY is analog. But after the slicer, RTTY
is discrete.
If I send cards for Hellscriber QSOs in for DXCC, I am almost sure
the ARRL would issue a "digital" certificate. But there is
absolutely nothing digital in that mode.
What the ARRL calls "digital" is probably better described as
"keyboard" or "character" based modes.
73
Chen, W7AY
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