# Impossible sampling theory!

Discussion in 'Electrical Engineering' started by Airy R. Bean, Dec 9, 2004.

1. ### Airy R. BeanGuest

A number of texts suggest that sampling can be modelled
by multiplying the incoming waveform by a comb of
Diracian Delta Functions.

How can this be?

1. The samples that you get are measured in the order
of single volts whereas the Diracian is infinitely tall. Surely,
if something of the order of unity were to be multiplied by
something of the order of infinity, the result would
be of the order of infinity?

How do you account for the difference? Do you have
some internal mental model where there is an invisible constant,
"Big K", perhaps, to account for the difference in scaling?

2. The area of the sampled pulse is very much less than unity,
the volts being ooo unity and the time being typically ooo usecs.

How do you handle this mentally when the area of the Diracian
is unity?

How do you come to terms with the attributes of your claimed model
being orders of magnitude different from the signals of the real world?

3. If you are one of those who claim that the sampled signal is a short
spike of zero width, then it is zero-integrable and not analysable by
any process involving Laplace Transforms.

How do you overcome the problem that your sampled signals are
not representable in the way that you claim?

2. ### Airy R. BeanGuest

And I haven't said it below. Are you a troll?

And what I denied ever saying was that every
textBOOK was wrong.

You'ew changing your goalposts by the minute.

3. ### Airy R. BeanGuest

Why would there be any texts that deny that "A number
of texts suggest that sampling can be modelled by multiplying
the incoming waveform by a comb of Diracian Delta Functions"?

What texts do you suggest would discuss other texts in that manner?

4. ### Airy R. BeanGuest

The only trolls in this NG would seem to be those
who clamour that the troll should not be fed. Often, as
in the case of Westcott below, their plaintiff moans
follow their showing themselves up with childish
outbursts which are then chastised without being risen
to.

Having been so chastised, they try to suggest that it is others
rather than they themselves as the originators of
childish posts who should be ostracised.

5. ### deBaserGuest

Hey a troll is for life not just for xmas. Do you know there are starving
trolls out there so give him all your [email protected]' money. Feed the troll, let
him know its xmas time

Bob Geldoff

6. ### Airy R. BeanGuest

How tall do you think it is for the multiplication
to take effect in a real circuit?

7. ### Kevin NeilsonGuest

One of my professors implied that the Dirac delta wasn't mathematically
rigorous but provides correct results so it's used nonetheless.

8. ### James BondGuest

how old are you beanie?

you cause a lot of problems. thats my observation

interesting indeed. whats in it for you? do you learn from this group? do
you provide input that others appreciate?

dr. x

9. ### Torkel FranzenGuest

You mean "plaintive".

10. ### Airy R. BeanGuest

It can be mathematically rigorous if you were
to use the curve borrowed from the Normal
Distribution of statistics, but it cannot
produce the correct results for the simple
reason that the pulses obtained are several orders of
magnitude different from the pulses in real circuits.

(And if you regard the pulses produced in real circuits
as existing only at a point, then those pulses are
not analysable)

In all aspects of engineering, the numbers that you
analyse are the physical values that arise in your
equipment. I wonder how others come to terms
with the fact that the numbers produced by the claim
that sampling is the multiplication by a comb of
Diracian are simply far, far too large?

Yes! I did!

12. ### PeterGuest

he's thinking he's in court once again!

13. ### NimrodGuest

Yawn and again Yawn.

The answers to the above are on google, I recall seeing you corrected on
this by Dr Reay.

14. ### Andrew ReillyGuest

On Thu, 09 Dec 2004 16:29:52 +0000, Airy R. Bean wrote:
[*Exactly* the same questions that he asked many moons ago, and
which have been answered completely in these groups, with both the
theoretical and practical rammifications thoroughly covered.]

You have provided no coherent or correct refutation of any of the
responses that were provided in the previous discussions.

Rather than asking the same questions again, I suggest that you use
followup questions if you feel that specific clarification is necessary.
Going back to your original post is unlikely to be more helpful another
time around.

15. ### Airy R. BeanGuest

Why not cite some of those responses and show

The answer is, that they did not, and merely repeated
parrot-fashion (or religionist fashion if you prefer) what
could be read from the text books. As I referred to such
textbook context initially, then those responses were meaningless,
other than, perhaps, to serve as an ego-trip for the posters.

16. ### Airy R. BeanGuest

First of all, shame on you for lowering the tone
by introducing the behavioural standards of the CBer.

That you are a CBer is indicated by your failing to realise
that Ham Radio is a technical pursuit, where interest in
technical development is the essence. DSP is now an increasing
part of the techiques developed by _REAL_ Radio Hams and
therefore any discussion relating to the understanding of DSP
is entirely relevant to Ham Radio.

(You're a CBer, so you won't have a clue about what the
above means, and so I append a short article to assist you.)

Ham Radio is a technical pursuit for those who
are interested in the science of radio wave
propagation and who are also interested in the
way that their radios function. It has a long-standing
tradition of providing a source of engineers who
are born naturals.

fascination with all things technical and gives
an all-abiding curiosity to improve one's scientific
knowledge. It's a great swimming pool, please dive in!

This excitement causes a wish to share the experience
with ones fellow man, and shows itself in the

Radio Hams are qualified to design, build and then
operate their own pieces of equipment. They do this
with gusto, and also repair and modify their own
equipment.

The excitement that drives a Radio Ham starts with
relatively simple technologies at first, perhaps making
his own Wimshurst machine and primary cells. Small pieces
of test equipment follow, possibly multimeters and signal
generators. Then comes receivers and transmitters. It is with
the latter that communication with like-minded technically
motivated people takes off. The scope for technical
development grows with the years
and now encompasses DSP and DDS. There is also a great deal
of excitement in the areas of computer programming to
be learnt and applied.

The technical excitement motivates Radio Hams to compete
with each other to determine who has designed and manufactured
the best-quality station. This competitiveness is found in DXing,
competitions and fox-hunts.

-----OOOOO----

However, beware! A Ham Radio licence is such a
desirable thing to have that there are large
numbers of people who wish to be thought of
as Radio Hams when, in fact, they are nothing
of the kind! Usually such people are a
radios off the shelf and send them back to be
repaired; they are not interested in technical discussion
and sneer at those who are; they have no idea how
their radios work inside and have no wish to find out;
they are free with rather silly personal insults;
they have not satisfied any technical qualification
and their licences prevent the use of
self-designed-and-built equipment.

These CB types engage in the competitive activities
in a forlorn effort to prove that they are Radio Hams.

No _REAL_ Radio Hams are deceived by such people!

17. ### Airy R. BeanGuest

There's no difficulty there because the infinite spectrum
of sinusoids cancel out to zero everywhere else
apart from the place at which they add constructively
to produce the pulse being analysed.

That they are zero everywhere else, including the
extremes of bipolar infinities means that the infinities
do not feature.

18. ### David KastrupGuest

You are confusing Fourier series with Fourier transform.
Nonsense. You are confusing Fourier series with Fourier transform.
Nonsense. You are confusing Fourier series with Fourier transforms.
Yup.

19. ### Eric JacobsenGuest

Gareth, this really is ridiculous. So many people have posted answers
to you that it isn't practical to even know where to start. You, on
the other hand, are the one claiming they're incorrect, so the burden
really is on you to explain why you think so.
This just oozes irony. Gushes. Floods.

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

20. ### Eric JacobsenGuest

Better watch out, Gareth, there's a guy here who hates it when people
post childish personal insults. You don't want to get on his bad
side.

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org