[RTTY] FW: OO Advisory kk5oq

[Kok Chen]

> I thought you may be interested to know your RTTY signal was 450 hz  
> wide
> vice the 'normal'  170 hz.

A normal RTTY signal has a shift of 170 Hz, but the -30 dB points are  
normally about 350 Hz to 450 Hz wide (even wider if you are using an  
FSK rig that has keyclicks).

The mystery deepens since it turns out that 450 Hz shift (mark tone  
is 450 Hz away from space tone) *is* one of the standards used in  
radioteletype,  just not used by hams.

Hams usually stick to 170 Hz or 850 Hz shifts, the latter at 75 baud.

So, if we assume that your signal *did* change to 450 Hz shift, the  
next question is were you using FSK or AFSK?

If you were using AFSK, it is some software in your computer that was  
responsible.  But if your were using FSK, then only your rig can be  
responsible for the wider shift.

A software modem could not have caused an FSK rig to change shift,  
since all the software does is to send the rig an FSK keying signal,  
although potentially some rig control software could have made the  
accidental switch.

73
Chen, W7AY