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From: Steve Thompson <>
Date: Thu, 01 Jun 2006 11:52:57 +0100
List-post: <>

Paul Christensen wrote:
> K7FM:
>> Rich talks about prayer cloths - but in fact his nichrome suppressor is
>> acting as a prayer cloth.  This is a case of putting that in will make 
>> sure
>> something bad will not happen.
> Fuses.
> Circuit breakers.
> Lightning arrestors:
> Discharge gaps.
> VSWR alarm circuits.
> Crowbar overvoltage protection.
> What do all these devices have in common with the parasitic suppressor? 
> Why, they are all "prayer cloths" designed to protect against something 
> can *could* happen, not necessarily something that is *pre-disposed* to 
> happen.

Another thing in common is that they are sometimes used without 
understanding of what they do; without knowing if they do anything 
useful; and without consideration of whether alternatives can offer the 
same result. Like parasitic suppressors, they will rarely add any 
problems - but is that a reason not to discuss why things oscillate, or 
different ways of preventing oscillation?
> So here we are -- more than a decade later since these parasitic debates 
> began and we're still debating the use of a one-dollar component in 
> multi-kilobuck amplifiers.
> If we hire the best design engineers who do the best job they know how 
> to ensure that every component selected for an appliance will test 
> in-tolerance, and stay in-tolerance during the product's life cycle, 
> should we then eliminate fuses as being an unnecessary "prayer cloth?"  
> Or, if I build my home in the safest part of the country where no known 
> floods, lightning, hurricanes, tornadoes, sink holes, excessive winds or 
> other nasty environmental factors exist -- am I smart in terminating my 
> homeowner's insurance policy?

Probably not, if you lose cover for fire, water leaks, accidental damage 
etc. As a different analogy, if you lived in San Francisco and had 
earthquake insurance, would you take out extra insurance against 
hurricanes? As you say, if it's cheap, why not, then it's something you 
don't have to think/worry about.

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