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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 4th September 2009, 04:41 PM   #941
jan.didden is offline jan.didden  Europe
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Originally Posted by jam View Post
That's Mr.Bessel to you Bob..............dropping names again?

Sorry, I couldn't resist.

Jam
It's also nonsense. There is a difference between name dropping as in 'I had lunch with Mr Bessel, therefore I am right' or invoking a mathematical process called a 'Bessel function' to explain something. I'm sure you get the not-so-subtle difference, Jam.

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Old 4th September 2009, 07:13 PM   #942
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Talk about 'name dropping'. In order to test a hunch, I asked Mitch Cotter, who had told me that he worked for the Fermi group in WW2, whether he had actually met and worked with Enrico Fremi, himself.
This is what he told me:
He and his other young associates were putting together a cyclotron, and had to align the magnetic assembly associated with it. Apparently, it takes some tweaking and adjustment to the magnetic fields to get it right. Well they were having problems, so they called in Enrico Fermi, himself.
He came, talked to everyone about the situation, then asked for someone to get him a dinner fork. Once, equipped with the fork, he went inside the cyclotron, felt around with the fork, and it was aligned in about 1 hour. How is that for a story.

Mitch also read what was here, this morning, and reminded me 'not to suffer fools, gladly' apparently a quote from Voltaire.
He also sent me some supporting material, but I can't make any sense of it, as applied to this specific situation. Would you like me to send it to you, Janneman? Perhaps you could post the relevant info from your website to this one, if you find something important.
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Old 4th September 2009, 07:24 PM   #943
john curl is offline john curl  United States
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Bob, I don't yet have the background to fully give you any real input on your questions. However if you look on p. 15-26 of the reference book: "Electronics Engineer's Reference Book' 4th edition, by L.W. Turner, you will see the added distortion pattern that is superimposed on the standard IM byproducts. Many other reference textbooks will give a similar pattern, when showing FM generation. The extra terms are composed of Fp-Fm and Fp+Fm as an example. I hope this helps.
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Old 4th September 2009, 07:31 PM   #944
Steve Eddy is offline Steve Eddy  United States
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Originally Posted by janneman View Post
It's also nonsense. There is a difference between name dropping as in 'I had lunch with Mr Bessel, therefore I am right' or invoking a mathematical process called a 'Bessel function' to explain something. I'm sure you get the not-so-subtle difference, Jam.
Jeeez, lighten up. He was only being facetious.

se
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Old 4th September 2009, 07:56 PM   #945
jan.didden is offline jan.didden  Europe
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Jeeez, lighten up. He was only being facetious.

se
OK, ok, you're right, I should.

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Old 4th September 2009, 07:57 PM   #946
jan.didden is offline jan.didden  Europe
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[snip]He also sent me some supporting material, but I can't make any sense of it, as applied to this specific situation. Would you like me to send it to you, Janneman? Perhaps you could post the relevant info from your website to this one, if you find something important.
Absolutely. Any documentation related to this I will gladly host.

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Old 4th September 2009, 08:09 PM   #947
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Originally Posted by john curl View Post
Bob, I don't yet have the background to fully give you any real input on your questions. However if you look on p. 15-26 of the reference book: "Electronics Engineer's Reference Book' 4th edition, by L.W. Turner, you will see the added distortion pattern that is superimposed on the standard IM byproducts. Many other reference textbooks will give a similar pattern, when showing FM generation. The extra terms are composed of Fp-Fm and Fp+Fm as an example. I hope this helps.
Exactly so, Fp+/-(2*k+/-1)*Fm where k is an integer, also related to the order of the Bessel functions, this is what everybody around is telling you.

So, how is this making the FM spectral components "harmonicly unrelated" and how large should be the FM modulation so that the +/- sidebands are significantly apart from Fp?
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Old 4th September 2009, 08:22 PM   #948
jan.didden is offline jan.didden  Europe
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[snip] Would you like me to send it to you, Janneman? Perhaps you could post the relevant info from your website to this one, if you find something important.
John, it is small enough to directly post it here for all to download etc. Since this appears to be from Wikipedia, it can probably be downloaded from there as well.

jd
Attached Files
File Type: pdf Frequency modulation synthesis.pdf (133.6 KB, 66 views)
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Old 4th September 2009, 08:23 PM   #949
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Well, they are sitting right there on the Graph that is fig. 3. Why don't you tell me, if you will just look at the graph.
I has emulated the FM modulation by FM modulating a 5KHz test tone with a 700 Hz modulation frequency and just playing with the modulation level. You can too!
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Old 4th September 2009, 08:34 PM   #950
jan.didden is offline jan.didden  Europe
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Originally Posted by john curl View Post
Well, they are sitting right there on the Graph that is fig. 3. Why don't you tell me, if you will just look at the graph.
I has emulated the FM modulation by FM modulating a 5KHz test tone with a 700 Hz modulation frequency and just playing with the modulation level. You can too!
Not sure who you address or what graph, but reading the posted piece it looks like inharmonic components are created with an inharmonic modulation frequency. How does that relate to the audio amp case discussed, I'm not sure, I'm skating on logic here, not on knowledge, I admit.

Anyway, inharmonic distortion does apparently occur in mechanical systems:

"Subharmonic and Nonharmonic Distortions Generated by High-Frequency Compression Drivers
Acoustical and electrical measurements are made of several commercial high frequency compression drivers with sine wave inputs at various power levels. The results show outputs containing not only the typical levels of upper harmonics, but also subharmonics and nonharmonically related content. These other distortion products are caused by certain modes of vibration of the domed diaphragm assembly. A review of parameter selections for the moving system of a compression driver is given.

Author: Hubbard, Jerry K.
Affiliation: Altec Lansing Corporation, Oklahoma City, OK
AES Conference:6th International Conference: Sound Reinforcement (May 1988)
Paper Number:6-029 "

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