[RTTY] FW: OO Advisory kk5oq

[Mike]

Hello Chen,

Good point about the "keyclicks" from the FSK set-ups.  Any ideas on 
what causes the 'clicks?  There were a number of stations that had 
them in the recent JARTS Contest.

At 11:47 AM 10/20/2005, Kok Chen wrote:
> > 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
>
>
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         73,
         Mike, K4GMH