[RTTY] rtty

[Kok Chen]

On Oct 3, 2008, at 2:26 PM, Art Searle W2NRA wrote:

> BTW he'd been on RTTY a little earlier on 17 meters
> and I couldn't copy him at all.  Since PSK counts towards
> RTTY DXCC I'm happy.

I have likewise gotten through to DX on PSK31 when RTTY could not get  
through.

However, there was one time (December 1999) when JA1WSK was operating  
PSK31 from PY0FT.  He was really loud on 20m, but I was also hearing a  
lot of (trans-equatorial) flutter from his signal.  Tried as much as I  
could, I could only pull an occasional character or two from him.  It  
is possible he was seeing the same thing, because he switched to RTTY  
not long after.  Although the flutter was obvious also on RTTY, I  
printed him well and made a QSO.

The next day, conditions improved, and I made a PSK31 QSO.

When conditions are good, with PSK31 you need only about 0 dB SNR over  
a 3 kc bandwidth to get moderately good print.  That is a signal that  
is just audible above the noise if you listen with an SSB filter.  So  
the "I worked him when I could barely hear him" claims are all true  
and not boasts.

It is possible in your case (not being able to work him on RTTY with  
whatever power, and being able to work him on higher power PSK), is  
happening because conditions are moderately good but signals are just  
weak (thus the need for power).

RTTY needs about 6 dB (4x) more power to achieve the same result as  
PSK31 when conditions are good.

However, as conditions deteriorate (multipath, flutter), PSK31 will no  
longer get through even if you can hear him loudly through an SSB  
filter (like my experience with PY0FT).  That is what I meant by not  
doing any good by raising power when there is multipath and flutter.

RTTY, on the other hand will get through flutter.

I think that in general, if you can print a PSK31 signal, then the  
path can't be that bad, so chances are also good that the reverse path  
is decent -- in which case,  if there is no QRM covering you up, he  
will be able to print you even if he can just barely hear you in a  
wide filter.

73
Chen, W7AY