Hmm might this be because ‘in the old days’ (amateur) RTTY was done with the rig in
LSB mode using AFSK?
With mark at 2125 Hz and space at 2295 hz and mark being
the idling position, when using LSB the actual transmitted frequencies would be
‘swapped’ (reversed)
So MTTY seems to assume rig at USB, while all (all?)
others assume LSB…
Still, Stefan and I seem to do RTTY wrong (i.e. amateur reversed,
as in AFSK on USB). I just checked
my PIC code and I have mark at high (DDS_BASE + 85 Hz) and space at low
(DDS_BASE). This then gets swapped around by fldigi because I listen (via
websdr) in USB… This explains why fldigi decodes me (and Stefan) just
right.
This is of course based on the assumption that ‘right’ means AFSK
on LSB, that the space must be the high tone AND the low(est) frequency.
What
_is_ the consensus (if any)?
73’s Minto pa3bca
--------------------------------------------------------------------------
Ceterum
censeo Carthaginem delendam esse
Sent: Wednesday, March 06, 2013 11:44
Subject: LF: RTTY Protocol
Graham
Just confirmed by
test, MMTTY is backwards compared to all other Software. Others idle on the high
tone MMTTY idles on the low, unless the REV is
pressed.
From Wiki
the upper tone used for
idle condition (MARK).
Another site says
You
also have to switch the correct phase position (whether the lower or higher
frequency carrier in frequency modulation corresponds to "Mark" or
"space").
Mind you a Ham education site on the subject
says.
Remember that bfo’s help filter out the carrier waves to allow for
the original signals to come through
Eddie
