That settles it. The info I got (from an untrusworthy source it seems) told
me mark is 2125 and space is 2295. See my original message below.
But it is the other way around.
But it is only independent of the sideband used if both sender and receiver
use the same sideband.... You still have to agree.
And it seems that the current consensus is mark = highest tone = highest
frequency. So USB if AFSK is used.
73’s Minto pa3bca
--------------------------------------------------------------------------
Ceterum
censeo Carthaginem delendam esse
Sent: Wednesday, March 06, 2013 13:57
Subject: Re: LF: RTTY Protocol
From my days on HF RTTY (~1970) with mechanical
'printers, the highest RF frequency was Mark (or idle tone) It was
independent of which sideband was used. I think this was also the mode used by
the commercial stations
Remember only European lines used bi-polar
signalling. The US used a 20mA mark and no current for space. A mechanical
machine of either type would chatter if the mechanism was not held in Mark.
Timing was mechanical and stop-start was necessary to maintain character timing
sync. with simple mechanical governors.
Alan G3NYK
----- Original Message -----
Sent: Wednesday, March 06, 2013 11:09
AM
Subject: Re: LF: RTTY Protocol
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
