Re: Filters & Chokes

["J. B. Weazle McCreath" <weazle-at-xxxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

At 05:46 PM 13/11/00 -0700, you wrote:
> Original poster: "Neil Chambers" <Neil_Chambers-at-paragon-it-dot-com>
> 
> Cripes
> 
> I'm just costing out the filter as per Terry's circuit diagram
> (http://hot-streamer-dot-com/TeslaCoils/Misc/NSTFilt.jpg) and at the UK prices
> I've found, it's gonna set me back over £110! £80 of that being the 100W
> wire-wound resisters.
> 
> Any cheaper options?!
> 
> Cheers
> 
> neil
>
Hello Neil,

I think that the 100 watt rating of the filter circuit resistors is much
larger than is really required.  Unless you intend to run your coil for
long continuous runs, about half that value should be more than enough.

In my own case, I have a two section filter circuit on my coil with two
400 ohm, 45 watt, resistors in each leg.  The common point of the two
resistors is bypassed to ground with a 500 pF. doorknob cap, and another
cap is connected from each HV bushing of the transformer to ground.
After runs of a minute or so, the resistors are just barely warm with a
measured input power of 1000 watts.

You can even parallel a number of smaller wattage resistors to give you
an equivalent resistance and wattage to one larger unit.  For instance,
three 1200 ohm, 15 watt, resistors equals one 400 ohm, 45 watt resistor.
In fact, due to more surface area, the group of three might radiate any
heat produced better than a single one would.

That's just my $.02 worth.


73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
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