Filter Selection

[Don Rasmussen]

Here is a question for anyone having a K3.

You are listening to a CW note on 40 meters at night
with moderate static, maybe S7 is the resting point.

Copying a signal using the standard roofing filter and
the DSP narrowed down to 500hz.

Now you open up the passband on the DSP to 2.7 khz and
activate a 500hz crystal filter.

First - can you do that?

Second - if you can, how much different does it sound?
I'd expect more pleasant listening experience in the
former scenario...
 

[Elecraft] Filter Selection
K4IA at aol.com K4IA at aol.com
Fri Nov 16 21:32:28 EST 2007


Wondering if a consensus was developing about  the
choice of roofing filters.
 Seems like there a too many to choose from.  Lacking
detailed plots for each
one, I can't believe there is that much  difference
between say a 500hz 5
pole and a 400hz 8 pole or a 200 hz 5 pole vs a  250
hz 8 pole.  Sure the 5 poles
will have wider skirts but will you be  able to hear
the difference?  

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[Craig Rairdin]

Yeah you can do that. There's a software update coming (or maybe it's
already out -- I haven't checked recently) that will make it easier. What
you would do is disable the 500hz filter and narrow the DSP to 500 hz, then
go to the CONFIG menu and enable the 500 hz filter. I think (but I'm not
sure) that the new software will immediately drop it in. The software I have
requires that you twiddle the WIDTH knob up or down a notch to make it
recognize the 500 hz filter is available.

My guess is it won't sound much different on a normal night on 40 m, but it
might be different in more crowded band conditions.

Craig
NZ0R

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Rasmussen
Sent: Friday, November 16, 2007 8:55 PM
To: Elecraft List
Subject: [Elecraft] Filter Selection


Here is a question for anyone having a K3.

You are listening to a CW note on 40 meters at night
with moderate static, maybe S7 is the resting point.

Copying a signal using the standard roofing filter and
the DSP narrowed down to 500hz.

Now you open up the passband on the DSP to 2.7 khz and
activate a 500hz crystal filter.

First - can you do that?

Second - if you can, how much different does it sound?
I'd expect more pleasant listening experience in the
former scenario...
 

[Elecraft] Filter Selection
K4IA at aol.com K4IA at aol.com
Fri Nov 16 21:32:28 EST 2007


Wondering if a consensus was developing about  the
choice of roofing filters.
 Seems like there a too many to choose from.  Lacking
detailed plots for each
one, I can't believe there is that much  difference
between say a 500hz 5
pole and a 400hz 8 pole or a 200 hz 5 pole vs a  250
hz 8 pole.  Sure the 5 poles
will have wider skirts but will you be  able to hear
the difference?  

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