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Re: LF: RTTY Protocol

To: <[email protected]>
Subject: Re: LF: RTTY Protocol
From: Minto Witteveen <[email protected]>
Date: Wed, 6 Mar 2013 12:09:50 +0100
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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
From: g3zjo
Sent: Wednesday, March 06, 2013 11:44
Subject: LF: RTTY Protocol

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


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