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From: Zen Cycle <funkmaster@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Fine Tuning Shifting
Date: Mon, 12 Aug 2024 13:15:35 -0400
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On 8/10/2024 4:56 PM, Jeff Liebermann wrote:
> On Sat, 10 Aug 2024 19:53:16 GMT, Tom Kunich <cyclintom@yahoo.com>
> wrote:
> 
>> Liebermann cannot even envision WHY I would use PWM since he probably has never owned a good oscilloscope.

No one can envision why you would use PWM to measure cable length 
because no one uses PWM to measure cable length, including you.

The method you described wasn't PWM.

We're still at the same point we were when you made this ridiculous 
claim 3 years ago - you haven't shown any published white paper, 
tutorial, app note, test equipment, or any references to using PWM for 
testing cable length other than your description which was completely 
faulty - you can't use a PWM generator and one channel on an 
oscilloscope to align a returned pulse.



> 
> 50% true.
> 
> You're correct that I can't envision why *YOU* would want to use PWM
> to measure cable length.  You're also correct that I would need to
> "envision" what you're doing.  You comment above was sufficiently
> grammatically awkward that I had to use a grammar checker to decode
> it.
> 
> 50% wrong.
> I still have far too many oscilloscopes:
> <https://www.learnbydestroying.com/jeffl/pics/home/test-equip-mess.jpg>
> <https://www.learnbydestroying.com/jeffl/crud/scopes-to-be-fixed.jpg>
> There are about 8 more scopes hidden in various corners or mounted in
> a rack.  Nobody seems to want the older oscilloscopes at any price.  I
> keep lusting after a nice new Rigol, but can't justify the expense.
> 
> I'm cleaning house right now and plan to eventually give away most of
> the oscilloscopes to hams, students, experimenters, builders and
> masochists.
> 
> I do own one LCD oscilloscope.  Something died inside and I haven't
> had time to fix it.  It's an Owon PDS 5022S.
> <https://www.google.com/search?q=owon+pds5022s&tbm=isch>
> 
> These days, I tend to use a computer and a cheap USB sound dongle for
> audio frequencies or something better for higher frequencies and more
> features:
> <https://www.google.com/search?q=usb+pc+oscilloscope&tbm=isch>
> 
>> And in some cases, time delays have to be measured down to the microsecond.
> 
> Huh?  Microsecond?  Light travels about 300 kilometers (186 miles) in
> 1 microsecond.  That's a rather large distance for measuring cable
> length.  If your mythical "some cases" require precision, you might be
> working in nanoseconds where light travels 30 cm (about 1 ft) in 1
> nanosecond.  Picoseconds would probably be better.

REmember Jeff, tommy is the one that thinks one can use Pulse Width 
Modulation to "to achieve time delay reflection"

https://groups.google.com/g/rec.bicycles.tech/c/f_tByXh5jXo/m/9Y4EzuUJCAAJ


> 
> 
> 

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