[Elecraft] K3 Receiver mush

[Dave Fugleberg]

Don, that's a great explanation. I came to the same conclusion in a recent
RTTY contest. I built my K3 with the single stock filter based on advice
from a number of folks to 'just operate for awhile til you get the feel for
what other filters you need'. I think that's sound advice.
Anyhow, I've been generally ok with the standard filter and relying on DSP
filtering to narrow it as needed. However, in the RTTY contest, I often had
issues working weaker stations when strong ones were very close by. It was
easy to see what was going on by watching the P3- I'd start copying a
signal inside the DSP bandwidth, and a strong one would pop up just above
or below that station. Even though I couldn't hear the strong station, the
weak one would go nearly silent as the AGC kicked in due to the strong
signal in the IF passband.
So, I think I've learned that I need a narrower filter for such situations.
I'm thinking a 400hz filter is what I want. Any reason for a different
selection in that scenario?
73 de W0ZF
On Tue, Feb 21, 2017 at 8:52 AM Don Wilhelm <donwilh at embarqmail.com> wrote:

> Mike,
>
> Think about it - if there are multiple signals in the passband, the AGC
> will respond to the strongest, there is just no way around that fact.
> If the signals can be separated by the DSP, and one is really strong,
> that strong station may be activating the Hardware AGC.  The only
> solution for the latter is a more narrow roofing filter - put the
> offending strong signal out of the passband of the roofing filter and
> use shift to get your sidetone for the desired signal back in order.
>
> That may be too much "fiddling" for a run station in a contest, but it
> is a viable way to operate when trying to copy a weak station working
> close to a strong station.
>
> 73,
> Don W3FPR
>
> On 2/21/2017 9:25 AM, W0MU Mike Fatchett wrote:
> > We noticed again during the contest hat when 3 or 4 stations called, all
> > those signals would be flattened to the same level. Once you got to
> > where one or two stations were calling the signal level would pop up
> > substantially.
> >
> > I have played endlessly with slope and threshold with little effect.
> >
> > My K3 has the new syn boards as well and filters from 2.8 to 2.5.
> > Latest firmware etc.
> >
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