[RTTY] To dash or not to dash - the bottom line

[Kok Chen]

On Jan 26, 2010, at 12:26 PM, Bill, W6WRT wrote:

> I'm not sure what you mean by "mixed shift" characters, but I will be
> glad to identify software which solves the whole problem neatly, and
> I'm sure the author would not be embarrassed at all.  :-)

Bill,

You reported a received exchange that printed as -QWE-QWE-QWE-QWE.

I can't think of any way that RTTY prints the above mixed shifting (LTRS shifted characters and FIGS shift characters mixed together without any spaces in between) unless extra FIGS and LTRS are intentionally sent.

If some software is printing that sequence on your machine, there is probably something wrong with it.

I.e., the only way the above can be received is that the sender  (whether it is USOS or non-USOS) has transmitted:

<FIGS>-<LTRS>QWE<FIGS>-<LTRS>QWE etc.

BTW, I just tested the K3 in FSK using the Morse paddle entry method to see if it uses USOS.

When you send "5<pause>5" in Morse from the CW paddle, cocoaModem (which has an option to display control characters) shows that the K3 generates "<figs>5<ltrs>[space]<figs>5".  Not really USOS.  

Basically, I think it generates a LTRS diddle when there is no immediate paddle activity, and by the time the pause is found to be long enough, it then finally sends a space (the system was already in LTRS shift at that point.  I.e., the K3 appears to send an extra LTRS if you send something like "599 123" when using the paddle in FSK.

I didn't check BPSK31 using a paddle on the K3, but I suspect that it also sends an extra idle Varicode before it sends a space character. You can think of the PSK idle and DominoEX beacon as having the same function as RTTY diddles (to keep the modulation active); in the case of DominoEX, the idle/diddle times are used to transmit a useful Beacon message).

And speaking of RTTY diddles, when I was experimenting with selectively faded RTTY signals, I had serendipitously discovered a very useful feature of diddles -- if you don't turn diddles on, a selective fade in the Space channel will cause the ATC to not properly track the slicer threshold when you are not typing.

73
Chen, W7AY