[WriteLog] bandwith for rtty

[Jim Brannigan]

I regularly use cascaded 250khz. filters for RTTY on my OMNI-VI.  You need
to tune the bandpass filter or it comes out like %VCSFT$!WQ@#

Jim


> The mostly likely problem for those of you using one of the SSB modes to
> receive RTTY signals is that the passband isn't centered correctly for
> tuning a RTTY signal when you have a narrow filter engaged. The normal
> center of the passband in SSB is somewhere around 1200Hz - with a 500Hz
> filter, you're only hearing the 950 to 1450Hz segment. But the RTTY signal
> is centered near 2125Hz, so you won't print it.
>
> Adjust the IF shift until the signals are strong and printable and you'll
> be in business.
>
> Alternatively, you can use "low tones" and receive RTTY signals in the SSB
> passband. It's not recommende for a few reasons, mainly because of the
> opportunity for harmonics when you transmit. With the normal "high" RTTY
> tones, the second harmonic is well out of the passband of the filters so
> it's suppressed naturally; on low tones, the second harmonic is at the
> upper end of the SSB passband.
>
> Many of us routinely use 250Hz filters with no issues at all, so it's not
a
> matter of bandwidth, but a matter of bandpass instead.
>
> -Marty NW0L
>   martyt@pobox.com
>
> At 08:14 AM 1/13/2002 , Alan Curson wrote:
> >Jay same setup here more or less.  I experience the same issues with
trying
> >to isolate the weaker signals using the .5 filter.  I have just suspected
> >that they are too narrow to tune effectively with just MMTTY software.
> >
> >John the AF Out is a jack on the back of the rig.  It is a "low level
> >receiver output for recording or external amplification."  (From the
manual)
> >The peak level is 100mVrms at 600 ohms.  It is not affected by the AF
> >control on the front panel but is affected by the digital fil controls on
> >the front.
> >
> >
> >
> > > > I have four filters on the radio. I found that I could copy
consistently
> > > > using the widest (2.4K) filter, generally OK using the 2.0K filter,
and
> > > not
> > > > at all with the narrower (.5 and .25) filters. This meant that I
could
> >not
> > > > isolate any of the weaker signals.
> > >
> > > Does the FT-990 allow the use of narrow filters in LSB mode?  If not,
> >that's
> > > it.  Funny, the 1000MP did allow that, but the newer MARK-V 1000MP
does
> >not.
> > > If this is the problem, use the PACKET jack - That one should've been
> > > labeled AFSK instead of PACKET!  Then press the PKT button on the from
and
> > > you'll be set to use the narrow filters.
> > >
> > > You mention "AF out", but you don't say where you're getting it from.
> > >
> > >
> > >
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