On 3/27/2012 10:42 AM, GeorgeWallner wrote:
> set the IF Filter to 600 Hz. This last one may
> sound counterintuitive, but I have found that: a) setting
> the filter too narrow results in ringing which stretches
> out the effects of a lightening crash, masking more of the
> signal, b) setting the K3's DSP filter narrower changes
> the shape of the CW pulses and makes them stand-out less,
Not counter-intuitive at all -- a fundamental property of filters is
that ringing occurs on impulses due to phase shift in the filter, which
for good filters, is greatest at the filter slopes and is proportional
to the steepness of the slope, so very narrow filters put that ringing
closer to the CW note. Ringing is also proportional to the amplitude of
the impulses and their rise time, which is why soft clipping can be
helpful if it doesn't add significantly to distortion in the passband.
I suspect that the superiority of the Collins mechanical filters in this
application may be due to a better behaved phase response in the passband.
73, Jim K9YC
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