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:[EMAIL PROTECTED]
Sent: Friday, November 30, 2007 8:52 PM
To: 'elecraft@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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Alan Bloom
Sent: Friday, November 30, 2007 1:47 PM
To: Darwin, Keith
Cc: elecraft@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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