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Hi Eddie, we were using line machines for a purpose
other than that for which they were designed :-)) The way round this
was to have some "special" operating methods which got lost when the ZX80 came
along.
On HF I remember sending RlsRlsR at the begining of
an over to ensure that the receiving machine had not slipped into figure shift
due to noise. On weak signals it was common to insert lots of extra ls. The
standard end of line was CRLFCR to ensure the carriage had time to get back to
the stop, before the text started. Many of the "ZX" ops didnt send any CR or LF
at all because their display wrapped......the Creed didn't!!
The QSO finished as a square black block at the end
of the line.
All good fun.
My mate G3YKB used to be on the LF reflector he was
editor of the BARTG newsletter around 1970.
Alan
G3NYK
----- Original Message -----
Sent: Wednesday, March 06, 2013 1:38
PM
Subject: Re: LF: Re: RTTY Protocol
On 06/03/2013 13:14, Minto Witteveen wrote:
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. Yes
yes.
BTW regarding missing the first character 's. In the mechanical
days did we not send CR/LF first to get things going? I have seen the software
have problems during the recent tests, printing Numbers instead of Letters.
This can be alleviated by sending 46RY first, 46 I think being RY with LetFig
set wrong.
Eddie
73’s Minto pa3bca
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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
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