[Test-Equipment] Q and filters

[David]

I do not disagree.  I am just saying that poor phase response is a choice when
designing bandpass filters and this can be traded off for filter shape.  Linear
phase response bandpass filters respond to an impulse with an output that has a
symmetrical envelope which could be considered to have less ringing but like you
say, the uncertainty is still there.

For voice applications this is irrelevant (unless a high Q section overloads)
but for data communications it can be important.  I believe the reason phasing
type modulators and demodulators have better voice characteristics is that the
channel had to be better designed anyway to preserve the amplitude and phase
response.

On Sun, 22 Jun 2014 19:18:06 +0000, you wrote:

>  Some how folks confuse linear phase response, bandpass ripple and ringing.
>Mathematically, you can't avoid ringing with narrow bandpass. You don't even have
>to use resonance to determine this. Just understanding simple Fourier transform. 
>  Fortunately both analysis agree. In fact one analysis leads to Heisenberg's uncertainty
>principle. 
>Delta F= bandwidth
>Delta T= time resolution or ringing so to speak
> delta F x delta T > 1, then using Plank's constant E=hF and simple algebra you get
> delta E x Delta T>h published in Heisenberg's first paper on the subject.
>This can be used to derive the relationship of position and momentum
>
>73
>Bill wa4lav
> 
>From: Test-Equipment [test-equipment-bounces at mailman.qth.net] on behalf of David [davidwhess at gmail.com]
>Sent: Sunday, June 22, 2014 1:58 PM
>To: Discussion of Electronic Test Equipment
>Subject: Re: [Test-Equipment] Q and filters
>
>From what I remember, the tradeoff is high Q versus higher order.  For a given
>bandwidth the two can be traded off and the later will yield a lower Q per
>section and cleaner phase response.
>
>On Sun, 22 Jun 2014 08:34:46 -0700, you wrote:
>
>>Hello Carl,
>>
>>~ Ive built several of his passive filters to get rid of high frequency
>>hiss, they work great compared to noisy and distorted active filters.
>>
>>What I can't quite believe is that it's possible to build a narrow passband
>>filter (high Q?) without ringing. Am I missing something here?
>>
>>Cheers,
>>
>>Brian