[time-nuts] "Q for dummies"

[Lux, Jim]

On 1/26/21 5:29 AM, Dave Daniel wrote:
> That doesn’t really illustrate the fundamental concept of Q. I’ll try and think of something that is still non-mathematical but nonetheless illustrates the concept of Q.
>
> DaveD

Ultimately, Q is about internal (or external) losses (leaving aside 
antennas) - how much energy is stored, vs (how much is radiated) or lost 
to heat

A big heavy pendulum will swing for a lot longer than a light one, 
because more energy is stored in the system, relative to the amount lost 
to air and mechanical friction.

And that, like the wine glass (which is a nice mechanical analogy - the 
fine crystal has less internal damping) is a "impulse response" system, 
not a "driven system"



But how that relates to bandwidth is a bit tricky, because then you need 
to get into a discussion "driven systems" and then into resonance - and 
that is where the train will come off the rails, particularly with 
respect to antennas.




>> On Jan 26, 2021, at 07:28, Ole Petter Ronningen <opronningen at gmail.com> wrote:
>>
>> Hi, All
>>
>> I am going to give a presentation to non-nuts, and in one of the slides I
>> touch on Q - not wanting to spend more than a sentence or two on the
>> subject, I wonder if the following analogy works:
>>
>> "A quality long-stemmed, thin-walled wine glass will ring for a long time
>> after we give it a little tap - this is high Q. A thick-walled, stubby milk
>> glass will barely ring at all, just a dull "plink" - this is low Q. The
>> energy we put in dies out very quickly."
>>
>> As I am sure is embarrassingly evident, I have a rather tentative grip on
>> the subject myself..
>>
>> Ole
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