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
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