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
