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Power protection toriod

Quoting Mike Mccarty:

 > Anyways, I'd like to dig a little deeper here.  Can you        
 > describe the construction of these chokes to me?  

You are going to love me for this: I take some some wire and wind
it around around ferrite toriod.

Generally I use a ferrite toroid about two inches in diameter. I
wind on 12 - 14 turns of insulated wire. 

 > It's my impression that these chokes as we are using them do   
 > very little filtering themselves but are a necessary part of   
 > the filter system to shift the phase angle 90 deg and keep the 
 > bypass capacitors (which ARE doing the filtering across the    
 > line) from looking into the tank circuit caps and acting in    
 > parallel with them. 

Actually the RF chokes by themselves do reduce the line noise
enough that you can measure a difference. But you are correct
that the filter system is much more effective.

 > By the way, how does one calculate the inductance needed for a 
 > choke like this in a given circuit?

I have no idea. I wound a few different types and sizes and
swapped them in the circuit while using a resonate pickup coil
to measure the RF line noise in the HV 60 cycle feed. There are
a lot of variables here. I do not feel that my rather simple
experiments and observations provided nearly enough data to be
conclusive, but this design does appear to work. 

Given your interest and knowledge on this subject perhaps you
would be able to research this further? I really did just blunder
along here: first I made observations from which I concluded that
some type of RF filter between the power supply and tank circuit
is very desirable; then I listened to the advice of other
experienced coilers (half of whom told me no filter is required);
then I designed some simple experiments to optimize and verify
the effectiveness of the filter I ended up using. I have tried
about five different sizes and types of chokes, and several
different values and types of bypass capacitors. But once I
obtained my goal of a workable filter, I went on to something
else.

Richard Quick



... If all else fails... Throw another megavolt across it!
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