On Jun 13, 2010, at 10:10 PM, Joe Subich, W4TV wrote:
> Even with the added bits the 8 bit code is slightly
> faster overall (146 ms/character vs, 165 ms) than 5 bit/45.45 baud.
I think I have mentioned earlier that 7-bit ASCII and 5-bit Baudot takes about
equal duration to transmit a typical contest exchanges even when both of them
use the *same* baud rate.
Counterintuitive? Perhaps.
The reason is the ASCII exchange won't have to transmit the numerous FIGS and
LTRS characters that you find in a Baudot exchange. The Baudot exchange
transmits shorter characters, but sends more of them. The ASCII exchange
contains longer characters, but fewer of them since there are no LTRS or FIGS
shift to send.
With exchanges that contain numbers between spaces (or even a number in between
alphabets of a callsign), the ASCII op actually spends less time sending a
typical contest exchange. With some other exchanges (e.g., if your callsign is
RAEM and you use dashes between exchange numbers, such as 599-123-123) the
Baudot op wins by a little. Overall, I think it is a wash in terms of printed
characters per second.
Remember too that you are not comparing 7 to 5, you are comparing 7+start+stop
to 5+start+stop.
ASCII used to be transmitted at 110 baud, 7 bit + 2 stop, no parity and 170 Hz
shift. But you do not *need* to switch to 110 baud when using ASCII.
The 110 baud number was probably determined by the then popular Model 33
Teletype. (Just as the Model 19 drove the 45.45 baud number.) You certainly
could keep using 45.45 baud or 75 baud as we do today with Baudot. I
personally think that 110 baud is needlessly fast for keyboard-to-keyboard QSO
and rather wasteful of bandwidth and comes with an increase in error rate.
The biggest impediment though, as Bob K0RC pointed out is that MMTTY lacks
ASCII capability.
73
Chen, W7AY
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