[RTTY] Dash vs space, more beat this to death

[Richard Ferch]

W6WRT wrote:

> I think you're right. If I recall correctly, when a space is detected by
> either the transmitter or receiver, they each reset themselves back to FIGS
> case, but no actual FIGS character is sent. The slowdown comes when the
> space is followed by more numbers, in which case another FIGS character is
> sent. If only letters are being sent, the space only causes a reset, not an
> actual sent character.
>
> Does that sound right?

Yes, but...

If the transmitting station is expecting the receiving station to be 
using USOS, it will transmit a [FIGS] whenever a space is followed by 
numbers, whereas if it is expecting the receiving station not to be 
using USOS, it doesn't bother. How does it know what to expect? Most 
likely, by looking at its own station's strategy on receive; that is, if 
you use USOS on receive, your most logical transmit strategy is to 
assume other stations are using USOS.

So, in the absence of errors, using a typical exchange with the serial 
number sent twice:

Non-USOS transmitter transmits [FIGS]599 123 123
Non-USOS receiver prints 599 123 123

Non-USOS transmitter transmits [FIGS]599 123 123
USOS receiver prints 599 QWE QWE - Oops!

USOS transmitter transmits [FIGS]599 [FIGS]123 [FIGS]123
Both receivers print 599 123 123

Either transmitter transmits [FIGS]599-123-123
Both receivers print 599-123-123

In other words, if you use USOS when you transmit (i.e. insert the extra 
[FIGS] characters), it doesn't matter what the receiving station does, 
it will always receive the intended message regardless of whether you 
use spaces or dashes (in the absence of errors, of course). If you don't 
use USOS when you transmit, then you had better use dashes between 
groups of numbers.

73,
Rich VE3KI