[RTTY] Kenwood IF filters ???
Joe Subich, W4TV
lists at subich.com
Thu Feb 18 15:48:03 PST 2010
> Is my logic correct? RTTY signals are "supposed" to
> be 170hz wide, so a 250hz filter would be optimal......
> yes/no.......(circle one hihi)
No. The RTTY shift is 170 Hz but there are keying
sidebands that are necessary to proper decoding. As
a rule of thumb you can add the shift plus three times
the baud rate to get the bandwidth of an FSK signal.
For 45.45 baud/170 Hz shift RTTY that works out to just
about 300 Hz. Since the cascaded 250 Hz filters are
supposedly -6dB at 250 Hz, that makes them just a bit
too narrow for RTTY (although some use them and accept
the additional loss). Cascaded 400 Hz filters would
be better on a theoretical basis ... both tones and
the keying sidebands will be within the "flat" part
of the filter response and not down on the skirts.
73,
... Joe, W4TV
> -----Original Message-----
> From: rtty-bounces at contesting.com
> [mailto:rtty-bounces at contesting.com] On Behalf Of David VE3VID
> Sent: Thursday, February 18, 2010 4:30 PM
> To: RTTY contest group
> Subject: Re: [RTTY] Kenwood IF filters ???
>
>
>
>
>
> Hmmmm ??? Okay. I am using MMTTY. WPX last week was my
> first contest. I wasn't aware MMTTY did filtering. My
> TS-450s has the stock filters for SSB: 6khz in the 8.83mhz
> passband an 2.4khz in 455khz IF. Obviously those filters are
> frustrating for RTTY.
>
> Show of hands please from users with TS-850s & TS-450s - 2 x
> 400hz filters for both IF stages, or 2 x 250hz filters in
> both. Is my logic correct? RTTY signals are "supposed" to
> be 170hz wide, so a 250hz filter would be
> optimal......yes/no.......(circle one hihi)
>
> Al (KE1FO) - why did you find the narrow filters frustrating?
> Can you comment on "MMTTY filtering"?
>
> David
> VE3VID
>
>
>
> > Date: Thu, 18 Feb 2010 12:57:29 -0500
> > Subject: Re: [RTTY] Kenwood IF filters ???
> > From: al at frugoli.info
> > To: ve3vid at hotmail.com
> >
> > Be careful. 400 is often as narrow as you wat to go, especially if
> > you're contesting. I find that the filtering MMTTY can do
> is adequite
> > in 99% of the cases with a 400hz filter.
> >
> > The TS940 I used to use had a 250 filter and it was
> frustrating when
> > trying to s&p during contests.
> >
> > 73 de AL, KE1FO
> >
> > On 2/17/10, David VE3VID <ve3vid at hotmail.com> wrote:
> > >
> > > Thanks for the Inrad URL Jim..........the 250hz filters
> would likely
> > > be exactly what I need
> > >
> > > :)
> > >
> > >
> > >
> > > David
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Date: Tue, 16 Feb 2010 14:55:23 -0800
> > > From: w6eu at sbcglobal.net
> > > To: ve3vid at hotmail.com
> > > Subject: Re: [RTTY] Kenwood IF filters ???
> > >
> > > http://www.inrad.net/home.php?xid=369e20e231649e0ad9497f17437841f8
> > >
> > > Try this website, David
> > >
> > > 73, Jim W6EU
> > >
> > >
> > > David VE3VID wrote:
> > > What is "Inrad".........a manufacturer? Do you know where
> they are
> > > available?
> > >
> > >
> > >
> > >
> > >
> > >
> > > From: ww3s at zoominternet.net
> > > To: ve3vid at hotmail.com
> > > Subject: Re: [RTTY] Kenwood IF filters ???
> > > Date: Tue, 16 Feb 2010 17:38:03 -0500
> > >
> > > I have an 850, but the filters are the same....I use a
> set of 400 hz
> > > Inrad in both IFs....
> > >
> > > On 2/16/2010 5:36:25 PM, David VE3VID (ve3vid at hotmail.com) wrote:
> > >
> > >
> > >
> > > Are you working RTTY with a Kenwood TS-450s? Which of the
> optional
> > > IF filters do you use? There are filters for the 455khz
> and 8.83mhz
> > > passbands. Which would work best for RTTY. I've done a
> little bit of
> > > RTTY without the filters just to cut my teeth, but the narrow IF
> > > filters are obviously necessary.............any infor would be
> > > appreciated.
> > >
> > >
> > >
> > > David
> > >
> > >
> > >
> > > VE3VID Located in rural Canada
> > > Solar power. Wood heat.
> > > Mosley tribander @ 22m
> > > 2element delta-quad on 40m
> > > Lots of space for dipoles,
> > > bears and wolves......73
> > >
> > > http://www.ve3vid.webs.com/
> > >
> > >
> > >
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> >
> > --
> > Sent from my mobile device
> >
> > 73 de Al, KE1FO
> >
> > -----
> > Check out my Amateur Radio Contesting blog at ke1fo.wordpress.com.
>
>
>
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