[RTTY] LMS Notch filter

[Jeff Blaine]

Harry,

I hear what you are saying.  But what looks good to a human eye as a filter
setting may not actually help the decoding.  A good example of this is the
guys raving about this or that crystal filter - and totally discount the
group delay impact as they go along not realizing it's the MMTTY decoder's
"ears" that are the ones that count.

The only MMTTY specific testing I've seen done was Dave's 512 profile
optimized for weak signal work.  And there I remember he was using the notch
in that config.  That's a vote in favor of using it.

Given the number of guys serious about RTTY, I would think there has been a
more serious look at it.  Of course, maybe guys have and it's falling in the
realm of "competitive advantage" so it's not showing up on the reflectors.
I would understand that as well.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Harry Coates
Sent: Friday, February 24, 2012 5:08 PM
To: Jeff Blaine
Cc: rtty at contesting.coms
Subject: Re: [RTTY] LMS Notch filter

Hi Jeff,
It sure is, you are only notching 2210hz...You will still have 2 nice narrow
signals for M & S at 2125 and 2295 with a deep notch between them, that has
nothing in it.. Don't confuse the receiving filter bandwidth with the MMTTY
tone filter bandwidth..You will have a
(noise-tone-noise) (nothing) (noise-tone-noise) signal.. Use the Show
feature to see what notch you are getting with the LMS settings.. Remember,
you can edit those settings..They are not fixed.. I then use a narrow BW
setting to get a nice bright yellow audio line with rather narrow noise
signals on each side.. Try it you can't hurt anything.. I just leave NOT
turned ON..
GO 4 IT,

Harry WA8HC


> Is there a benefit when using a twin peak filter (of whatever 
> implementation) - assuming there is only one signal within the passband?
>
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
>
> -----Original Message----- 
> From: Harry Coates
> Sent: Friday, February 24, 2012 3:43 PM
> To: rtty at contesting.com
> Subject: [RTTY] LMS Notch filter 
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