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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: the apple test
Date: Wed, 1 Jan 2025 17:11:02 -0000 (UTC)
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On Wed, 01 Jan 2025 07:45:20 -0800, john larkin wrote:

> On Wed, 1 Jan 2025 01:05:40 -0000 (UTC), Cursitor Doom
> <cd999666@notformail.com> wrote:
> 
>>On Tue, 31 Dec 2024 18:11:38 -0500, Edward Rawde wrote:
>>
>>> "john larkin" <jl@glen--canyon.com> wrote in message
>>> news:sls8nj55tqh3u77h1vqbnvffs0vjjd7oo3@4ax.com...
>>>> On Tue, 31 Dec 2024 17:30:55 -0500, DJ Delorie <dj@delorie.com>
>>>> wrote:
>>>>
>>>>>john larkin <jl@glen--canyon.com> writes:
>>>>>> Close your eyes and imagine an apple in front of your face. Can you
>>>>>> see it? In detail, in color? Can you rotate it on any axis and see
>>>>>> it moving? Can you look down on it from the top and see which way
>>>>>> the stem points?
>>>>>
>>>>>The important thing to remember is... there is no apple.
>>>>
>>>> Apples are real.
>>> 
>>> Except imaginary ones.
>>> 
>>> But some imaginary things might be real.
>>> https://www.youtube.com/watch?v=T647CGsuOVU
>>
>>They're real alright. You can't describe things like complex impedance
>>or the plotting of a Smith Chart without recourse to them.
> 
> Certainly complex impedances can be visualized and analyzed in  time
> domain. Better than in classic slide-rule-days RF terms.

There certainly is a highly useful role for TD in this area. In fact by 
using a TDR and a VNA together one can disintangle multiple reflections on 
a network and uncover discontinuities that are obscured by other 
reflections. I really should get a TDR; it's about the only piece of test 
kit (apart from a curve tracer) I don't own. Must remedy those 
shortcomings as a priority!