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[AMPS] Water dielectric?

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Subject: [AMPS] Water dielectric?
From: (2)
Date: Tue, 31 Jul 2001 09:54:41 -0700
>> > >>  It seems, on the surface, that one could dip a small air variable in
>> > >>(pure) water and have a high voltage part with 80x the capacity of the
>> > >>original.
>> >Or, if not water, some non-conductive liquid.  Don't have a dielectric
>> >chart handy, but there must be something suitable.
>> Transformer oil (or nearly any mineral oil) would work quite well.  The
>> dielectric constant typically is just over 2.0, and the voltage insulating
>> characteristics are excellent.  A good application would be for the tune
>> cap on 160 or 80 meters : a 150 or 200 pf, 1000V air variable would become
>> a 300 or 400 pf HV variable cap.
>When you look around and see the industry avoiding a method 
>there is almost always a good reason. In this case they are 
>probably concerned about loss of Q and heating of the component.
>Dissipation factor is the ratio of energy dissipated to energy stored 
>per cycle. The dissipation factor would increase greatly if you pick 
>the wrong material.
>As a second effect when you add a dielectric, energy is more 
>concentrated. There is more current in a smaller area. That also 
>can increase losses if you don't plan for it.
/\  So make the plates out a good conductor.  

>A third effect is drift. The component will change values with 
>You need to look at more than capacitance.
>Many materials also have an increase in dissipation factor with 

/\ good points, Mr. Rauch.  If there had been something better, Joe 
Jennings would likely have chosen it over the vacuum dielectric in his 
variable capacitors.  


-  R. L. Measures, 805.386.3734,AG6K,  

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