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Hi Eddie I did hear of the polarised solenoid
losing their magnetism, but not in those circumstances, interesting! Did it
recover or did it need repolarising or replacement? I had a couple of Mod 54
that were 7E with a cranked frame (makes the paper easierto read) and an
all-over very effective silence cover ex NCB I think.
Alan
----- Original Message -----
Sent: Wednesday, March 06, 2013 7:52
PM
Subject: Re: LF: Re: RTTY Protocol
Hi Alan
Yes interesting.
I had a Creed 7B?
Rattler as well as my Z80 microprocessor set up, so I kept compatible with the
mechanical methods. The Creed was in the garage and I sent to it via
co-ax for any hard copy and also printing tickets for local do's on card, a
man with a printer was a rarity.
I wonder if you ever came across a
problem I had one winter, the Creed stopped printing and I found that the
magnet had permanently lost its magnetism due to extreme cold.
73
Eddie
On 06/03/2013 19:03, Alan Melia wrote:
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
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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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