[RTTY] FW: OO Advisory kk5oq

[DJ3IW Goetz]

Hi,

I worked Charles, KK5OQ on 16 October, 1615UTC on 15m and I
did NOT notice a wide shift.

73 de Goetz, DJ3IW
----- Original Message ----- 
From: "Kok Chen" <chen at mac.com>
To: "Anderson, Charles, MSG, 255ACS, SCS, 6820" 
<Charles.Anderson at msjack.ang.af.mil>
Cc: <k7ovg at velocitus.net>; <rtty at contesting.com>
Sent: Thursday, October 20, 2005 3:47 PM
Subject: Re: [RTTY] FW: OO Advisory kk5oq


>> 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
>