[RTTY] Dashes in Contest Reports

[Kok Chen]

On Jan 25, 2010, at 1/25    8:41 AM, Jim Reisert AD1C wrote:

> There is NO call for 5NN ever in a RTTY contest!

Jim has the best advice so far.

Morse cut numbers have no place in Baudot encoding, and in this case,  
also lengthens the exchange.

One good reason to keep an exchange short is to reduce the time of the  
exchange to produce the least confusing print at the other end when in  
the presence of noise.

If you can send the same information with fewer channel symbols, there  
is less likelihood that there will be garbled print on the receiving  
screen among your transmitted characters.

You can observe this especially well by watching PSK31 contests, where  
lower case and upper case characters have drastically different  
channel symbol lengths.  I have seen Simon, HB9DRV (the author of Ham  
Radio Deluxe) mention this more than once.

In the case of RTTY, there is an additional factor in addition to  
superfluous Baudot LTRS/FIGS shift characters that can be garbled into  
a (wrong) printing character -- and that is the cross compatibility  
between USOS and non-USOS systems.

Any time a space occurs between Baudot characters, it can cause  
incompatibility between USOS and non-USOS systems.  A space right  
after a number will cause the receiver of the USOS system to shift  
from FIGS into LTRS shift by itself, while the space character does  
nothing to the state of the non-USOS system.

The maximum incompatibility, if you transmit using USOS, comes when  
you type something like "599 OR".  When you send that with a USOS  
transmitter, it will be received as "599 94" by a non-USOS receiver.   
If you repeat the transmission with "599 OR OR OR", it will be read as  
"599 94 94 94".  However, if you send "599-OR" whether with a USOS or  
non-USOS transmitter, it will be received as "599-OR" by either a USOS  
or non-USOS receiver (it should be obvious since the systems only  
differ when you send a space character).

The maximum incompatibility, if you transmit with a non-USOS  
transmitter, is when you send "599 123".  A USOS receiver will receive  
it as "599 QWE".  Even if you send a repeat in the form "599 123 123  
123" it will still be read as "599 QWE QWE QWE".  However, if you send  
"599-123" from a non-USOS transmitter, it will be read as "599-123" by  
both a USOS and a non-USOS receiver.  Again, the compatibility is  
obvious since we have avoided using spaces.

(A minus/dash symbol is in the FIGS table and will cause no extra LTRS/ 
FIGS transitions when it is used between numbers.)

You can attempt to decree that all contesters use USOS by putting it  
in the contest rules as the "code" that you must use (after all, it is  
decreed that we use Baudot and 45.45 baud).  But since many novices  
have never even heard of USOS, much less know what it actually does,  
it seems prudent to send an exchange that is compatible with both  
systems as long as both systems are in use.

In the meantime, one thing you can do might be to include a "repeat"  
macro that use dashes if you are using spaces in the regular  
exchange.  And to include a macro to transmit with spaces if you are  
using dashes in regular exchanges.

I have seen so many blank stares about USOS that I had included a  
short paragraph to explain USOS when I wrote the RTTY section in the  
Digital Modes chapter of the 2010 ARRL Handbook.  I might be involved  
with the 2011 Handbook too, so if you think there are other protocol  
related topics that should be included in the RTTY, PSK31 or MFSK16  
sections, please send suggestions to me -- I already plan on expanding  
the DominoEX section in the next go around since I have in the  
meantime studied in detail how DominoEX works.

73
Chen, W7AY