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Posted: Tue Oct 26, 2010 12:09 pm
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La capa de 1 micro permettra une chemin RF vers la masse car la resistance de 220K + le pot donne une haute impedance sur ce noeud par rapport au chemin vers la masse tel que initialement il y avait avec la capa de découplage (celle après la 33K).

The low ESR cap is a RF short to ground, it's EMI immunity.

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Posted: Tue Oct 26, 2010 3:03 pm
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Interesting Tissan, I will look at this.

C'est une idée intéressante Tissan, je vais étudier ta suggestion, Merci, thank you.


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Posted: Tue Oct 26, 2010 11:20 pm
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Tissan that is an excellent method to keep the bias circuit clean ! I'll have to try that. I think this would be a good place to use a Solen fast cap I have sitting around. Thanks, Art

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Posted: Wed Oct 27, 2010 8:43 pm
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Tissan, that would be the same idea as using a film cap at 1:100 ratio to bypass any electrolytic filter cap, right ? Art

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Posted: Wed Oct 27, 2010 11:01 pm
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Aclempopi, basically yes for decoupling, it's a thumb rule (1:10 to 1:100, this is linked to ESR of each cap that you see for its own resonance, if you are interest I can give you a "spice freeware" for cap dimensioning DC to RF). However, in Stratele52 case, it's a little bit different because when he changed the schematic he unfortunatly removes the RF path + "long wire" + high impedance = antenna then risk of buzz or parasitic noise.

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Posted: Thu Oct 28, 2010 1:22 am
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This is a good thread.

That is all.

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Posted: Thu Oct 28, 2010 2:31 am
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However, in Stratele52 case, it's a little bit different because when he changed the schematic he unfortunatly removes the RF path + "long wire" + high impedance = antenna then risk of buzz or parasitic noise.

Tissan

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Good information Tissan, thank's


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Posted: Thu Oct 28, 2010 5:26 pm
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Yes Tissan, I would appreciate that info on "cap demensioning". Thanks , Art

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Posted: Fri Oct 29, 2010 1:30 pm
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Refer to the following:

http://www.kemet.com/kemet/web/homepage ... en/kemsoft

Download the soft, install it. Just try.
8)

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Posted: Sat Oct 30, 2010 1:58 am
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Tissan ,I will download this softwear too. I must say that I don't know very much about this "ESR" and 1:10 to 1:100 ratio.
I have some books talking about that, I should read it.
Thank's for the very good information, I'll buy a 1 mfd cap.

I have some questions about output transformer. I'll start a post about that.


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Posted: Sat Oct 30, 2010 1:46 pm
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ESR = Equivalent Serial Resitor.
Actually, a cap can be seen in 5 zones:
DC =Open circuit (0Hz)
C-band = frequency range where the cap is a cap (20MHz)
ESR-band = frequency range where the cap is a resistor (resonnance at 30MHz))
L-band _frequency range where the cap is a coil (200Mhz)
Parasitic band = frequency range where the cap resonates on internal geometry (3GHz)

Note that the values in Hz are only an examples.

Then if you want to make a good decoupling especially in RF, you have to put a couple of cap in // with a ration of 1:10 to 100 in order to maintain the impedance to the lowest value by ESR of each cap.

(just to make sure I was talking about 1µF (micro) not milli --> mfd)

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Posted: Sun Oct 31, 2010 1:29 am
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Good information Tissan, I have to study that.


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