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Re: RF Chokes + Bypass caps = resonant rise?




From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Friday, November 21, 1997 6:40 PM
To: 	Tesla List
Subject: 	Re: RF Chokes + Bypass caps = resonant rise?

Hi Adam,

> From:   Adam[SMTP:absmith-at-tiac-dot-net]
> Sent:   Thursday, November 20, 1997 1:10 AM
> To:     tesla list
> Subject:    RF Chokes + Bypass caps = resonant rise?
> 
> 
> I just thought of something kind of disturbing.  It occured to me that 
> the 2mH RF chokes I borrowed from my small coil setup, in combination 
> with my 500pF bypass caps, should have a cutoff freq. of 160kHz.  Now, my 
> current larger coil with it's big toroid operates at almost exactly 
> 160kHz, so this is really bad- especially dangerous with no damping DC 
> resistance.  I suspect that these small chokes are actually working 
> against me in this new setup!  I am removing the chokes, and I will 
> probably try to replace them with 10mH values or bigger, so that any kick 
> back from the tank is dropped across the choke, not across the bypass 
> caps!
> 
> Any thoughts? Am I correct to do this?
> 
> -Adam

Yes - go bigger and usethe smallest wire you can get away with for
max choke current (contributes to killing their Q).

Malcolm