[RTTY] RTTY and Emergency Communication

[Kok Chen]

On Jan 6, 2009, at 1/6    8:14 AM, Lee Buller wrote:

> During the RU...I was working stations all over the country and  
> even the world with good copy.

Well, some of the stations that you copied were using a whole load of  
power, too.

Even PSK31, under the same average power, will out perform RTTY under  
quiet band conditions.  RTTY has an edge when conditions deteriorate  
-- you can still get through if you apply enough power.  When  
conditions are poor, PSK31 just won't work anymore, no matter how  
much power you use.

Because of the envelope shaping, PSK31 stations that uses 100 watt  
tranceivers can only run a maximum of about 50 watts.  Yet, on a good  
day, you can hear signals all over the place in the PSK31 part of  
20m.  Lots of stations didn't even know I was calling them during the  
Roundup with my 50 watts and verticals -- now and then I had pushed  
it to 100 watts just to be heard.

Unlike PSK31, MFSK16 and Olivia can work under very terrible  
conditions using very low power.  Both are multitone FSK after all,  
they just has more tones than the two Mark and Space in RTTY, and  
they don't take up that much more bandwidth than RTTY.

MT63 is a mode that is preferred by emergency operations today.   
However, it is a much wider bandwidth mode.  I guess bandwidth usage  
does not matter in an emergency.

The fact that RTTY is restricted to the 5 bit Baudot code is also an  
impediment.  All the modern modes can take a much larger character  
set without the LTRS/FIGS hack that so cripple RTTY in terms of error  
rates.   The lack of an interleaver and FEC are also hurting RTTY  
during long QSB.

IMHO, RTTY is good for fast transmit/receive turnarounds (thus good  
for contesting and DXpeditions) but does not hold a candle to other  
modern modes when it comes to robustness.

During the RTTY Welcome day, I had established contact with W8TTY.   
But he was getting terrible copy from me.  I noticed that the path  
was in pretty decent shape, so we QSY to PSK31 and had a very  
pleasant hour long QSO.

73
Chen, W7AY