RE: [TCML] Filter Choice

["Lau, Gary" <Gary.Lau@xxxxxx>]

A Terry filter and the EMI filter you cited on eBay are two completely different beasts.  Neither one replaces the other.  The Terry filter is used to filter "bad stuff" between the main spark gap and the NST, for the purpose of protecting the NST.  The EMI filter is used to keep "bad stuff" from passing from the NST primary back into your mains wiring, in an attempt to minimize interference to radios, TV's, etc.  I have an EMI filter wired into my coil too, mostly because EMI filters are cheap and there's no down-side to using one.  But there's no doubt that radio reception in my house, and likely beyond, is affected, regardless.

IMHO, the Terry filter is the more valuable asset.  If you had to choose one, that's the one.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Scott
> Sent: Saturday, February 23, 2008 6:04 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Filter Choice
>
> Hello again guys.  The troubleshooting tips I got here on my first post led
> me to replace my NST and as a result my coil is now resonating, thanks to
> all.
>
> Now that I'm onto tuning, I would like to protect the power supply systems
> before I do any runs longer than a few seconds.  The construction of a
> safety gap, variable power output, ext. are within my technical grasp, but I
> would like some advice on a choice of filter.
>
> >From what I have read, I need a RC low pass filter installed after the HV
> outputs of the NST.  A Terry Filter seemed like the only choice, but I have
> been coming across these:
> http://cgi.ebay.com/RFI-EMI-Tesla-Filter-2-x-20-Amps-115-
> 250vac_W0QQitemZ140208669619QQihZ004QQcategoryZ7288QQssPageName
> ZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting
> on ebay and local industrial shops.  Is this something different than a
> Terry Filter?  Would I want both?  Is there a cheaper filter solution from a
> Terry Filter or place to buy them commercially  They seem rather expensive
> to build from scratch.  Thanks for the answers, my coil specs are:
>
> 60hz 9kv NST @ 30ma, secondary balanced midpoint ground
> 0.0085 uF caps @ 17600 volts
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