2.13 beta

[Robert Paull]

Hi all:
So I loaded 2.13 and I can now only drop to 150 hz in data mode, not 50 like I was able to with 2.10
Any one else seeing this.
Thanks
Bob
KK6UE
k3 681


     
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[KK7P]

> ...I can now only drop to 150 hz in data mode, not 50 like I was able to with 2.10
> Any one else seeing this.

50 Hz and 100 Hz BW are available in PSK D.

The reason they are not available in other data modes is because they
are not applicable (AFSK and FSK D), or the fact that the center
frequency allowed for the sharpest FIR filters is limited to something
under 2 kHz makes them not general.

73,

Lyle KK7P

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[Joe Subich, W4TV-3]

Lyle,

> 50 Hz and 100 Hz BW are available in PSK D.
>

With a 1500 Hz center frequency the narrow filter should be made
available in DATA A.  I would also argue that it should be made
available in AFSK A if MARK <> 2125 (e.g. CF=1000Hz or 1360Hz).
Both DATA A and AFSK A are useful for PSK31 which can benefit
from the ultra narrow filtering.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Lyle Johnson
> Sent: Thursday, July 03, 2008 11:59 PM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] 2.13 beta
>
>
> > ...I can now only drop to 150 hz in data mode, not 50 like
> I was able
> > to with 2.10 Any one else seeing this.
>
> 50 Hz and 100 Hz BW are available in PSK D.
>
> The reason they are not available in other data modes is because they
> are not applicable (AFSK and FSK D), or the fact that the center
> frequency allowed for the sharpest FIR filters is limited to
> something
> under 2 kHz makes them not general.
>
> 73,
>
> Lyle KK7P
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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[Julian, G4ILO]

Joe Subich, W4TV-3 wrote

With a 1500 Hz center frequency the narrow filter should be made
available in DATA A.  I would also argue that it should be made
available in AFSK A if MARK <> 2125 (e.g. CF=1000Hz or 1360Hz).
Both DATA A and AFSK A are useful for PSK31 which can benefit
from the ultra narrow filtering.

Is there any benefit in using such a narrow flter for PSK? The DSP decoder is only looking at the actual band of frequencies containing the signal so it is, in effect, a narrow band filter already. The only possible benefit I can see is if a strong close-in signal is activating AGC causing the weak one to be depressed into the noise, but if it is that close IMD products from the strong signal are probably going to make decoding the weak one a lost cause anyway.

[Robert Paull]

Hi Lyle:
I agree with Joe if I am using psk (data A) there are a lot of times I need filters below 150 hz. PSK having the least bandwidth requirement of the data modes I would have thought you would have kept it at below 150 hz.

Just my 2 cents worth

Bob, KK6UE

--- On Fri, 7/4/08, Joe Subich, W4TV <[hidden email]> wrote:

> From: Joe Subich, W4TV <[hidden email]>
> Subject: RE: [Elecraft] 2.13 beta
> To: "'Lyle Johnson'" <[hidden email]>, [hidden email]
> Cc: [hidden email]
> Date: Friday, July 4, 2008, 12:36 AM
> Lyle,
>
> > 50 Hz and 100 Hz BW are available in PSK D.
> >
>
> With a 1500 Hz center frequency the narrow filter should be
> made
> available in DATA A.  I would also argue that it should be
> made
> available in AFSK A if MARK <> 2125 (e.g. CF=1000Hz
> or 1360Hz).
> Both DATA A and AFSK A are useful for PSK31 which can
> benefit
> from the ultra narrow filtering.
>
> 73,
>
>    ... Joe, W4TV
>  
>
>
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of
> Lyle Johnson
> > Sent: Thursday, July 03, 2008 11:59 PM
> > To: [hidden email]
> > Cc: [hidden email]
> > Subject: Re: [Elecraft] 2.13 beta
> >
> >
> > > ...I can now only drop to 150 hz in data mode,
> not 50 like
> > I was able
> > > to with 2.10 Any one else seeing this.
> >
> > 50 Hz and 100 Hz BW are available in PSK D.
> >
> > The reason they are not available in other data modes
> is because they
> > are not applicable (AFSK and FSK D), or the fact that
> the center
> > frequency allowed for the sharpest FIR filters is
> limited to
> > something
> > under 2 kHz makes them not general.
> >
> > 73,
> >
> > Lyle KK7P
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> >  http://mailman.qth.net/mailman/listinfo/elecraft   
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com

     
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[Jim Brown-10]

On Fri, 4 Jul 2008 00:50:36 -0700 (PDT), G4ILO wrote:

>Is there any benefit in using such a narrow flter for PSK? The DSP decoder
>is only looking at the actual band of frequencies containing the signal so
>it is, in effect, a narrow band filter already.

Narrow filters reduce the amplitude of impulse noise, like lightning static
and many forms of QRN. Impulse noise can push gain stages, including audio
stages and the output transformers, into clip, which can make life more
difficult for any decoder. Going from 150 Hz to 50 Hz bandwidth reduces the
power of that impulse noise by 4.8 dB.

On the other hand, any sharp filter skirt can introduce ringing from that
noise, and very narrow filters bring that ringing closer to the signal. AND,
any change in amplitude response (i.e., the filter skirts) MUST introduce
phase shift, which can get in the way of decoding. In other words, there may
be a point of diminishing returns. This is one of those questions that must be
answered by experimentation, and will likely vary from one decoder to another.

W0YK is a very serious RTTY contester, and has been using K3s since the
earliest stages of beta. I'd bet that Ed could tell us a lot about these
issues with respect to RTTY decoding. :)  

73,

Jim K9YC


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