[Elecraft] K3 Filter questions

[Thomas Horsten]

I haven't looked at the spec for the 1.8 filter but I second what Dave was
saying, the specified filter bandwidths are (I think) -3dB and the curve is
obviously not completely straight down, so there is still signals outside
the passband.

I have told my K3 that the 400Hz CW filters are really 500Hz, which means
the 2.1kHz filter only kicks in when I move above 500Hz, which allows me a
slightly wider passband e.g. when calling CQ, this works extremely well for
me, and from looking at the waterfall the extra 50Hz on each side are
getting through the filter well enough.

I'm sure operating the 1.8kHz filter as a 2.1 one would work as well,
although I never tried it myself, it might actually be a better setup than
the 2.1 filter for contest use.

73, Thomas M0TRN

On 27 March 2012 19:12, <k.igor at comcast.net> wrote:

>
>
> I am pretty sure the DSP filter is effective only  if it is narrower than
> the roofing filter. In your setup the DSP filter is pretty much  turned
> off. Please, don't forget, the crystal filters in K3 are ROOFING filters,
> they are protecting next IF stages and the DSP from strong near by signals,
> improving dynamic range . The main filtering is done in DSP. There is white
> paper on the matter somewhere on Elecraft web site (by Eric S).
>
>
>
> 73,
>
> Igor, N1YX
>
>
>
> ----- Original Message -----
>
>
> From: "Dave Hachadorian" <k6ll at arrl.net>
> To: "Elecraft Reflector" <elecraft at mailman.qth.net>
> Sent: Tuesday, March 27, 2012 12:52:51 PM
> Subject: Re: [Elecraft] K3 Filter questions
>
> I used the 1.8 for the entire WPX SSB contest, with a DSP width
> of 2.1 KHz.  It sounded great.  I never messed with any of the
> settings for the entire contest.  To get this combination of
> DSP=2.1 and crystal=1.8, one has to install the 1.8 filter as if
> it were a 2.1, so it switches in at DSP=2.1.  This installation
> setup is most easily done using the K3 Utility.  In practice,
> normalize, then use high cut until the filter switches in.  To
> me, the audio sounds best using that technique.  WPX SSB is
> traditionally the worst-case QRM-fest, and the 1.8 filter was
> just the ticket for dealing with it.
>
> Dave Hachadorian, K6LL
> Yuma, Arizona
>
>
> >From experience, I had both the 2.1 and 1.8 fitted and by
> >judicious use of
> the Hi Cut/Lo Cut adjustment I find the 1.8 far better in
> practice.
>
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