[Elecraft] K3 filters

[Bill W5WVO]

Ron,

Isn't it funny that whenever you accidentally omit a word from a sentence, 
it's always the one word that completely alters the meaning of the sentence in 
the most significant way possible?  :-)

I believe this is yet another corollary to Murphy's Law...

Bill / W5WVO
(Technical Writer/Editor/Artist in my other life)



Ron D'Eau Claire wrote:
> Oops I meant to say:
>
> "Ringing is a function of the bandwidth and only SLIGHTLY affected by
> the type of filter."
>
> -----Original Message-----
> From: Ron D'Eau Claire [mailto:ron at cobi.biz]
> Sent: Friday, November 30, 2007 8:52 PM
> To: 'elecraft at mailman.qth.net'
> Subject: RE: [Elecraft] K3 filters
>
>
> Any filter will produce "ringing" when the bandwidth is too small.
>
> Ringing is a function of the bandwidth and only affected by the type
> of filter. In some filter designs it's possible for some elements of
> the filter to have such a high Q they ring even though the overall
> filter bandpass is not that small, but that's a aberration in the
> filter design.
>
> Ringing typically occurs when the bandwidth at either the transmitter
> or receiver is restricted too much to allow the CW sidebands to pass
> through.
>
> Of course, the sidebands on a CW signal are the frequencies
> represented by the rise and fall of each CW element. If the bandwidth
> isn't sufficient to pass them, the element is stretched out in time
> as the amplitude decays, just like the amplitude of a bell decays
> after the bell was stuck. That's what we call "ringing".
>
> Ron AC7AC
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Alan Bloom
> Sent: Friday, November 30, 2007 1:47 PM
> To: Darwin, Keith
> Cc: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] K3 filters
>
>
> For the same passband ripple and bandwidth I think more poles pretty
> much invariably means more ringing.
>
> By the way, many people think that DSP-based filters don't ring.
> Actually, a digital filter's impulse response, measured at say the
> half-power point, is pretty comparable to an analog (e.g. cyrstal)
> filter with the same ripple and bandwidth.  However, the ringing from
> a digital FIR (finite impulse response) filter eventually drops all
> the way to zero, while an IIR (e.g. analog) filter theoretically
> rings forever.  Since human sound perception tends to be logarithmic,
> the ringing _sounds_ longer with the analog filter.
>
> Al N1AL
>
>
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